matiec: comparison stage1

equal deleted inserted replaced

-:a8263f33123f
+:f55ef301e14c
 * This means that bison cannot handle it without some
 * caoxing from ourselves. We will then need this token
 * to do the coaxing...
 */
 %token BOGUS_TOKEN_ID
 %type <leaf>	start
 %type <leaf>	any_identifier
 %type  <leaf>	action_time
 %type  <leaf>	indicator_name
 %type  <leaf>	transition
 %type  <leaf>	steps
 %type  <list>	step_name_list
+%type  <leaf>	transition_priority
 %type  <leaf>	transition_condition
 %type  <leaf>	action
 %type  <leaf>	transition_name
 prev_declared_derived_function_block_name: prev_declared_derived_function_block_name_token {$$ = new identifier_c($1, locloc(@$));};
 prev_declared_program_type_name: prev_declared_program_type_name_token {$$ = new identifier_c($1, locloc(@$));};
 /***************************/
 /* B 0 - Programming Model */
 /***************************/
 library:
 /* empty */
 | library library_element_declaration
 	{$$ = $1; $$->add_element($2);}
 /* ERROR_CHECK_BEGIN */
 | library error END_OF_INPUT
 	{$$ = NULL;
-	 print_err_msg(current_filename, locf(@2), locl(@2), "unknown error.");
+	 print_err_msg(current_filename, locf(@2), locl(@2), "unknown syntax error.");
 	 yyerrok;
 	}
 /* ERROR_CHECK_END */
 ;
 	{$$ = new integer_literal_c($1, $3, locf(@1), locl(@3));}
 /* NOTE: see note in the definition of constant for reason
 * why signed_integer, binary_integer, octal_integer
 * and hex_integer are missing here!
 */
+/* ERROR_CHECK_BEGIN */
+| integer_type_name signed_integer
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "'#' missing between integer type name and value in integer literal.");
+	}
+| integer_type_name binary_integer
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "'#' missing between integer type name and value in integer literal.");
+	}
+| integer_type_name octal_integer
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "'#' missing between integer type name and value in integer literal.");
+	}
+| integer_type_name hex_integer
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "'#' missing between integer type name and value in integer literal.");
+	}
+| integer_type_name error signed_integer
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "expecting '#' between integer type name and value in integer literal.");
+	 yyerrok;
+	}
+| integer_type_name error binary_integer
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "expecting '#' between integer type name and value in integer literal.");
+	 yyerrok;
+	}
+| integer_type_name error octal_integer
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "expecting '#' between integer type name and value in integer literal.");
+	 yyerrok;
+	}
+| integer_type_name error hex_integer
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "expecting '#' between integer type name and value in integer literal.");
+	 yyerrok;
+	}
+| integer_type_name '#' error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid value for integer literal.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 signed_integer:
 integer
 | '+' integer   {$$ = $2;}
 real_literal:
 signed_real
 | real_type_name '#' signed_real
 	{$$ = new real_literal_c($1, $3, locf(@1), locl(@3));}
+/* ERROR_CHECK_BEGIN */
+| real_type_name signed_real
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "'#' missing between real type name and value in real literal.");
+	}
+| real_type_name error signed_real
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "expecting '#' between real type name and value in real literal.");
+	 yyerrok;
+	}
+| real_type_name '#' error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid value for real literal.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 /* helper symbol for non_negative_numeric_literal */
 non_negative_real_literal:
 non_negative_signed_real
 /* NOTE: see note under the B 1.2.1 section of token
 * and grouping type definition for reason why the use of
 * bit_string_type_name, although seemingly incorrect, is
 * really correct here!
 */
+/* ERROR_CHECK_BEGIN */
+| bit_string_type_name integer
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "'#' missing between bit string type name and value in bit string literal.");
+	}
+| bit_string_type_name binary_integer
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "'#' missing between bit string type name and value in bit string literal.");
+	}
+| bit_string_type_name octal_integer
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "'#' missing between bit string type name and value in bit string literal.");
+	}
+| bit_string_type_name hex_integer
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "'#' missing between bit string type name and value in bit string literal.");
+	}
+| bit_string_type_name error integer
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "expecting '#' between bit string type name and value in bit string literal.");
+	 yyerrok;
+	}
+| bit_string_type_name error binary_integer
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "expecting '#' between bit string type name and value in bit string literal.");
+	 yyerrok;
+	}
+| bit_string_type_name error octal_integer
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "expecting '#' between bit string type name and value in bit string literal.");
+	 yyerrok;
+	}
+| bit_string_type_name error hex_integer
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "expecting '#' between bit string type name and value in bit string literal.");
+	 yyerrok;
+	}
+| bit_string_type_name '#' error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid value for bit string literal.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 boolean_literal:
 TRUE	{$$ = new boolean_literal_c(new bool_type_name_c(locloc(@$)),
 	{$$ = new duration_c(new neg_time_c(locloc(@$)), $4, locloc(@$));}
 | T_SHARP interval
 	{$$ = new duration_c(NULL, $2, locloc(@$));}
 | T_SHARP '-' interval
 	{$$ = new duration_c(new neg_time_c(locloc(@$)), $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| TIME interval
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "'#' missing between 'TIME' and interval in duration.");
+	}
+| TIME '-' interval
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "'#' missing between 'TIME' and interval in duration.");
+	}
+| TIME error interval
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "expecting '#' between 'TIME' and interval in duration.");
+	 yyerrok;
+	}
+| TIME error '-' interval
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "expecting '#' between 'TIME' and interval in duration.");
+	 yyerrok;
+	}
+| TIME '#' error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid value for duration.");
+	 yyerrok;
+	}
+| T_SHARP error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "invalid value for duration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 interval:
 days
 /*| integer ('d') ['_'] hours */
 | integer_d hours
 	{$$ = new days_c($1, $2, locloc(@$));}
 | integer_d '_' hours
 	{$$ = new days_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| integer_d '_' error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid value for hours in duration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 hours:
 /*  fixed_point ('h') */
 /*| integer ('h') ['_'] minutes */
 | integer_h minutes
 	{$$ = new hours_c($1, $2, locloc(@$));}
 | integer_h '_' minutes
 	{$$ = new hours_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| integer_h '_' error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid value for minutes in duration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 minutes:
 /*  fixed_point ('m') */
 fixed_point_m
 /*| integer ('m') ['_'] seconds */
 | integer_m seconds
 	{$$ = new minutes_c($1, $2, locloc(@$));}
 | integer_m '_' seconds
 	{$$ = new minutes_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| integer_m '_' error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid value for seconds in duration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 seconds:
 /*  fixed_point ('s') */
 fixed_point_s
 /*| integer ('s') ['_'] milliseconds */
 | integer_s milliseconds
 	{$$ = new seconds_c($1, $2, locloc(@$));}
 | integer_s '_' milliseconds
 	{$$ = new seconds_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| integer_s '_' error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid value for milliseconds in duration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 milliseconds:
 /*  fixed_point ('ms') */
 fixed_point_ms
 /* B 1.2.3.2 - Time of day and Date */
 /************************************/
 time_of_day:
 TIME_OF_DAY '#' daytime
 	{$$ = new time_of_day_c($3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| TIME_OF_DAY daytime
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "'#' missing between 'TIME_OF_DAY' and daytime in time of day.");
+	}
+| TIME_OF_DAY error daytime
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "expecting '#' between 'TIME_OF_DAY' and daytime in time of day.");
+	 yyerrok;
+	}
+| TIME_OF_DAY '#' error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid value for time of day.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 daytime:
 day_hour ':' day_minute ':' day_second
 	{$$ = new daytime_c($1, $3, $5, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| day_hour day_minute ':' day_second
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "':' missing between hours and minutes in daytime.");
+	}
+| day_hour error day_minute ':' day_second
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "expecting ':' between hours and minutes in daytime.");
+	 yyerrok;
+	}
+| day_hour ':' ':' day_second
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@3), "no minutes defined in daytime.");
+	}
+| day_hour ':' error ':' day_second
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "invalid value for minutes in daytime.");
+	 yyerrok;
+	}
+| day_hour ':' day_minute day_second
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@3), locl(@4), "':' missing between minutes and seconds in daytime.");
+	}
+| day_hour ':' day_minute error day_second
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@3), locl(@5), "expecting ':' between minutes and seconds in daytime.");
+	 yyerrok;
+	}
+| day_hour ':' day_minute ':' error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@4), locl(@4), "invalid value for seconds in daytime.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 day_hour: integer;
 day_minute: integer;
 date:
 DATE '#' date_literal
 	{$$ = new date_c($3, locloc(@$));}
 | D_SHARP date_literal
 	{$$ = new date_c($2, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| DATE date_literal
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "'#' missing between 'DATE' and date literal in date.");
+	}
+| DATE error date_literal
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "expecting '#' between 'DATE' and date literal in date.");
+	 yyerrok;
+	}
+| DATE '#' error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid value for date.");
+	 yyerrok;
+	}
+| D_SHARP error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid value for date.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 date_literal:
 year '-' month '-' day
 	{$$ = new date_literal_c($1, $3, $5, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| year month '-' day
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "'-' missing between year and month in date literal.");
+	}
+| year error month '-' day
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "expecting '-' between year and month in date literal.");
+	 yyerrok;
+	}
+| year '-' '-' day
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@3), "no month defined in date literal.");
+	}
+| year '-' error '-' day
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "invalid value for month in date literal.");
+	 yyerrok;
+	}
+| year '-' month day
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@3), locl(@4), "':' missing between month and day in date literal.");
+	}
+| year ':' month error day
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@3), locl(@5), "expecting ':' between month and day in date literal.");
+	 yyerrok;
+	}
+| year ':' month ':' error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@4), locl(@4), "invalid value for day in date literal.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 year: integer;
 month: integer;
 date_and_time:
 DATE_AND_TIME '#' date_literal '-' daytime
 	{$$ = new date_and_time_c($3, $5, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| DATE_AND_TIME date_literal '-' daytime
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "'#' missing between 'DATE_AND_TIME' and date literal in date and time.");
+	}
+| DATE_AND_TIME error date_literal '-' daytime
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "expecting '#' between 'DATE_AND_TIME' and date literal in date and time.");
+	 yyerrok;
+	}
+| DATE_AND_TIME '#' '-' daytime
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "no value defined for date literal in date and time.");
+	}
+| DATE_AND_TIME '#' error '-' daytime
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid value for date literal in date and time.");
+	 yyerrok;
+	}
+| DATE_AND_TIME '#' date_literal daytime
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "'-' missing between date literal and daytime in date and time.");
+	}
+| DATE_AND_TIME '#' date_literal error daytime
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "expecting '-' between date literal and daytime in date and time.");
+	 yyerrok;
+	}
+| DATE_AND_TIME '#' date_literal '-' error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid value for daytime in date and time.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 */
 data_type_declaration:
 TYPE type_declaration_list END_TYPE
 	{$$ = new data_type_declaration_c($2, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| TYPE END_TYPE
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no data type declared in data type(s) declaration.");
+	}
+| TYPE error type_declaration_list END_TYPE
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unexpected token after 'TYPE' in data type(s) declaration.");
+	 yyerrok;
+	}
+| TYPE error END_TYPE
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unknown error in data type(s) declaration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 /* helper symbol for data_type_declaration */
 type_declaration_list:
 type_declaration ';'
 	{$$ = new type_declaration_list_c(locloc(@$)); $$->add_element($1);}
 | type_declaration_list type_declaration ';'
 	{$$ = $1; $$->add_element($2);}
+/* ERROR_CHECK_BEGIN */
+| type_declaration error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "';' missing at end of data type declaration.");
+	 yyerrok;
+	}
+| type_declaration_list type_declaration error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "';' missing at end of data type declaration.");
+	 yyerrok;
+	}
+| type_declaration_list ';'
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "unexpected ';' after data type declaration.");
+	}
+/* ERROR_CHECK_END */
 ;
 type_declaration:
 single_element_type_declaration
 | array_type_declaration
 /*  simple_type_name ':' simple_spec_init */
 identifier ':' simple_spec_init
 	{$$ = new simple_type_declaration_c($1, $3, locloc(@$));
 	 library_element_symtable.insert($1, prev_declared_simple_type_name_token);
 	}
+/* ERROR_CHECK_BEGIN */
+| identifier simple_spec_init
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "':' missing between data type name and specification in simple type declaration.");
+	}
+| identifier ':' identifier
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@3), locl(@3), "unknown data type defined in specification for data type declaration.");
+	}
+| identifier ':' error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "no specification defined in data type declaration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 simple_spec_init:
 simple_specification
 */
 | elementary_type_name ASSIGN constant
 	{$$ = new simple_spec_init_c($1, $3, locloc(@$));}
 | prev_declared_simple_type_name ASSIGN constant
 	{$$ = new simple_spec_init_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| elementary_type_name constant
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "':=' missing in specification with initialization.");
+	}
+| prev_declared_simple_type_name constant
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "':=' missing in specification with initialization.");
+	}
+| identifier ASSIGN constant
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "unknown type defined in specification.");
+	}
+/* ERROR_CHECK_END */
 ;
 /* When converting to C/C++, we need to know whether
 * the elementary_type_name is being used in a variable
 * declaration or elsewhere (ex. declaration of a derived
 /*  subrange_type_name ':' subrange_spec_init */
 identifier ':' subrange_spec_init
 	{$$ = new subrange_type_declaration_c($1, $3, locloc(@$));
 	 library_element_symtable.insert($1, prev_declared_subrange_type_name_token);
 	}
+/* ERROR_CHECK_BEGIN */
+| identifier subrange_spec_init
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "':' missing between data type name and specification in subrange type declaration.");
+	}
+/* ERROR_CHECK_END */
 ;
 subrange_spec_init:
 subrange_specification
 	{$$ = new subrange_spec_init_c($1, NULL, locloc(@$));}
 | subrange_specification ASSIGN signed_integer
 	{$$ = new subrange_spec_init_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| subrange_specification signed_integer
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "':=' missing in subrange specification with initialization.");
+	}
+/* ERROR_CHECK_END */
 ;
 subrange_specification:
-integer_type_name '(' subrange')'
+integer_type_name '(' subrange ')'
 	{$$ = new subrange_specification_c($1, $3, locloc(@$));}
 | prev_declared_subrange_type_name
 {$$ = new subrange_specification_c($1, NULL, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| integer_type_name '(' ')'
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@3), "no subrange defined in subrange specification.");
+	}
+| integer_type_name '(' error ')'
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "invalid subrange defined in subrange specification.");
+	 yyerrok;
+	}
+| integer_type_name '(' subrange error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@3), locl(@3), "')' missing after subrange defined in subrange specification.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 subrange:
 signed_integer DOTDOT signed_integer
 	{$$ = new subrange_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| signed_integer signed_integer
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "'..' missing between bounds in subrange definition.");
+	}
+| signed_integer error signed_integer
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "expecting '..' between bounds in subrange definition.");
+	}
+| signed_integer DOTDOT error
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "invalid value for upper bound in subrange definition.");
+	}
+/* ERROR_CHECK_END */
 ;
 enumerated_type_declaration:
 /*  enumerated_type_name ':' enumerated_spec_init */
 identifier ':' enumerated_spec_init
 	{$$ = new enumerated_type_declaration_c($1, $3, locloc(@$));
 	 library_element_symtable.insert($1, prev_declared_enumerated_type_name_token);
 	}
+/* ERROR_CHECK_BEGIN */
+| identifier enumerated_spec_init
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "':' missing between data type name and specification in enumerated type declaration.");
+	}
+/* ERROR_CHECK_END */
 ;
 enumerated_spec_init:
 enumerated_specification
 	{$$ = new enumerated_spec_init_c($1, NULL, locloc(@$));}
 | enumerated_specification ASSIGN enumerated_value
 	{$$ = new enumerated_spec_init_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| enumerated_specification enumerated_value
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "':=' missing in enumerated specification with initialization.");
+	}
+/* ERROR_CHECK_END */
 ;
 enumerated_specification:
 '(' enumerated_value_list ')'
 	{$$ = $2;}
 | prev_declared_enumerated_type_name
+/* ERROR_CHECK_BEGIN */
+| '(' ')'
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no enumerated value list defined in enumerated specification.");
+	}
+| '(' error ')'
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "invalid enumerated value list defined in enumerated specification.");
+	 yyerrok;
+	}
+| '(' enumerated_value_list error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "')' missing at the end of enumerated specification.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 /* helper symbol for enumerated_specification */
 enumerated_value_list:
 enumerated_value
 	{$$ = new enumerated_value_list_c(locloc(@$)); $$->add_element($1);}
 | enumerated_value_list ',' enumerated_value
 	{$$ = $1; $$->add_element($3);}
+/* ERROR_CHECK_BEGIN */
+| enumerated_value_list enumerated_value
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "',' missing in enumerated value list.");
+	}
+| enumerated_value_list ',' error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "invalid value in enumerated value list.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 enumerated_value:
 identifier
 {$$ = new enumerated_value_c(NULL, $1, locloc(@$));}
 | prev_declared_enumerated_type_name '#' any_identifier
 	{$$ = new enumerated_value_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| prev_declared_enumerated_type_name any_identifier
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "'#' missing between enumerated type name and value in enumerated literal.");
+	}
+| prev_declared_enumerated_type_name error any_identifier
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "expecting '#' between enumerated type name and value in enumerated literal.");
+	 yyerrok;
+	}
+| prev_declared_enumerated_type_name '#' error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid value for enumerated literal.");
+	 yyerrok;
+	}
+| identifier '#' any_identifier
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "unknown type name for typed literal.");
+	}
+/* ERROR_CHECK_END */
 ;
 /*
 enumerated_value_without_identifier:
 /*  array_type_name ':' array_spec_init */
 identifier ':' array_spec_init
 	{$$ = new array_type_declaration_c($1, $3, locloc(@$));
 	 library_element_symtable.insert($1, prev_declared_array_type_name_token);
 	}
+/* ERROR_CHECK_BEGIN */
+| identifier array_spec_init
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "':' missing between data type name and specification in array type declaration.");
+	}
+/* ERROR_CHECK_END */
 ;
 array_spec_init:
 array_specification
 	{$$ = new array_spec_init_c($1, NULL, locloc(@$));}
 | array_specification ASSIGN array_initialization
 	{$$ = new array_spec_init_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| array_specification array_initialization
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "':=' missing in array specification with initialization.");
+	}
+/* ERROR_CHECK_END */
 ;
 array_specification:
 prev_declared_array_type_name
 | ARRAY '[' array_subrange_list ']' OF non_generic_type_name
 	{$$ = new array_specification_c($3, $6, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| ARRAY array_subrange_list ']' OF non_generic_type_name
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "'[' missing before subrange list in array specification.");
+	}
+| ARRAY error array_subrange_list ']' OF non_generic_type_name
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "expecting '[' after 'ARRAY' in array specification.");
+	 yyerrok;
+	}
+| ARRAY '[' ']' OF non_generic_type_name
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@3), "no subrange list defined in array specification.");
+	}
+| ARRAY '[' error ']' OF non_generic_type_name
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "invalid subrange list defined in array specification.");
+	 yyerrok;
+	}
+| ARRAY OF non_generic_type_name
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no subrange list defined in array specification.");
+	}
+| ARRAY error OF non_generic_type_name
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "invalid subrange list defined in array specification.");
+	 yyerrok;
+	}
+| ARRAY '[' array_subrange_list OF non_generic_type_name
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@3), locl(@4), "']' missing after subrange list in array specification.");
+	}
+| ARRAY '[' array_subrange_list error OF non_generic_type_name
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@3), locl(@5), "expecting '[' after subrange list in array specification.");
+	}
+| ARRAY '[' array_subrange_list ']' non_generic_type_name
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@4), locl(@5), "'OF' missing between subrange list and item type name in array specification.");
+	}
+| ARRAY '[' array_subrange_list ']' error non_generic_type_name
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@4), locl(@6), "expecting 'OF' between subrange list and item type name in array specification.");
+	 yyerrok;
+	}
+| ARRAY '[' array_subrange_list ']' OF error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "no itme data type defined in array specification.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 /* helper symbol for array_specification */
 array_subrange_list:
 subrange
 	{$$ = new array_subrange_list_c(locloc(@$)); $$->add_element($1);}
 | array_subrange_list ',' subrange
 	{$$ = $1; $$->add_element($3);}
+/* ERROR_CHECK_BEGIN */
+| array_subrange_list subrange
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "',' missing in subrange list.");
+	}
+| array_subrange_list ',' error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid subrange in subrange list.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 array_initialization:
 '[' array_initial_elements_list ']'
 	{$$ = $2;}
+/* ERROR_CHECK_BEGIN */
+| '[' ']'
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no initial values list defined in array initialization.");
+	}
+| '[' error ']'
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "invalid initial values list defined in array initialization.");
+	 yyerrok;
+	}
+| '[' array_initial_elements_list error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "']' missing at the end of array initialization.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 /* helper symbol for array_initialization */
 array_initial_elements_list:
 array_initial_elements
 	{$$ = new array_initial_elements_list_c(locloc(@$)); $$->add_element($1);}
 | array_initial_elements_list ',' array_initial_elements
 	{$$ = $1; $$->add_element($3);}
+/* ERROR_CHECK_BEGIN
+| array_initial_elements_list ',' error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid array initial value in array initial values list.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 array_initial_elements:
 array_initial_element
 | integer '(' ')'
 | integer '(' array_initial_element ')'
 	{$$ = new array_initial_elements_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN
+| integer '(' error ')'
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "invalid array initial value in array initial values list.");
+	 yyerrok;
+	}
+| integer '(' array_initial_element error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "')' missing at the end of array initial value in array initial values list.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 array_initial_element:
 constant
 /*  structure_type_name ':' structure_specification */
 identifier ':' structure_specification
 	{$$ = new structure_type_declaration_c($1, $3, locloc(@$));
 	 library_element_symtable.insert($1, prev_declared_structure_type_name_token);
 	}
+/* ERROR_CHECK_BEGIN */
+| identifier structure_specification
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "':' missing between data type name and specification in structure type declaration.");
+	}
+/* ERROR_CHECK_END */
 ;
 structure_specification:
 structure_declaration
 initialized_structure:
 prev_declared_structure_type_name
 	{$$ = new initialized_structure_c($1, NULL, locloc(@$));}
 | prev_declared_structure_type_name ASSIGN structure_initialization
 	{$$ = new initialized_structure_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| prev_declared_structure_type_name structure_initialization
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "':=' missing in structure specification with initialization.");
+	}
+| identifier ASSIGN structure_initialization
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "unknown type name for structure specification with initialization.");
+	}
+/* ERROR_CHECK_END */
 ;
 structure_declaration:
 STRUCT structure_element_declaration_list END_STRUCT
 	{$$ = $2;}
+/* ERROR_CHECK_BEGIN */
+| STRUCT END_STRUCT
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no structure element declared in structure type declaration.");
+	}
+| STRUCT error structure_element_declaration_list END_STRUCT
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unexpected token after 'STRUCT' in structure type declaration.");
+	 yyerrok;
+	}
+| STRUCT error END_STRUCT
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unknown error in structure type declaration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 /* helper symbol for structure_declaration */
 structure_element_declaration_list:
 structure_element_declaration ';'
 	{$$ = new structure_element_declaration_list_c(locloc(@$)); $$->add_element($1);}
 | structure_element_declaration_list structure_element_declaration ';'
 	{$$ = $1; $$->add_element($2);}
+/* ERROR_CHECK_BEGIN */
+| structure_element_declaration error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "';' missing at end of structure element declaration.");
+	 yyerrok;
+	}
+| structure_element_declaration_list structure_element_declaration error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "';' missing at end of structure element declaration.");
+	 yyerrok;
+	}
+| structure_element_declaration_list ';'
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "unexpected ';' after structure element declaration.");
+	}
+/* ERROR_CHECK_END */
 ;
 structure_element_declaration:
 structure_element_name ':' simple_spec_init
 	{$$ = new structure_element_declaration_c($1, $3, locloc(@$));}
 | structure_element_name ':' array_spec_init
 	{$$ = new structure_element_declaration_c($1, $3, locloc(@$));}
 | structure_element_name ':' initialized_structure
 	{$$ = new structure_element_declaration_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| structure_element_name simple_spec_init
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "':' missing between structure element name and simple specification.");
+	}
+| structure_element_name subrange_spec_init
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "':' missing between structure element name and subrange specification.");
+	}
+| structure_element_name enumerated_spec_init
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "':' missing between structure element name and enumerated specification.");
+	}
+| structure_element_name array_spec_init
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "':' missing between structure element name and array specification.");
+	}
+| structure_element_name initialized_structure
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "':' missing between structure element name and structure specification.");
+	}
+| structure_element_name ':' identifier
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "unknown variable type defined in structure element declaration.");
+	}
+| structure_element_name ':' error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "no specification defined in structure element declaration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 structure_element_name: any_identifier;
 structure_initialization:
 '(' structure_element_initialization_list ')'
 	{$$ = $2;}
+/* ERROR_CHECK_BEGIN */
+| '(' error ')'
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "invalid structure element initialization list in structure initialization.");
+	 yyerrok;
+	}
+| '(' structure_element_initialization_list error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "expecting ')' at the end of structure element initialization list in structure initialization.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 /* helper symbol for structure_initialization */
 structure_element_initialization_list:
 structure_element_initialization
 	{$$ = new structure_element_initialization_list_c(locloc(@$)); $$->add_element($1);}
 | structure_element_initialization_list ',' structure_element_initialization
 	{$$ = $1; $$->add_element($3);}
+/* ERROR_CHECK_BEGIN
+| structure_element_initialization_list structure_element_initialization
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "',' missing in structure element initialization list in structure initialization.");
+	}
+| structure_element_initialization_list ',' error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid structure element initialization in structure initialization.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 structure_element_initialization:
 structure_element_name ASSIGN constant
 	{$$ = new structure_element_initialization_c($1, $3, locloc(@$));}
 | structure_element_name ASSIGN array_initialization
 	{$$ = new structure_element_initialization_c($1, $3, locloc(@$));}
 | structure_element_name ASSIGN structure_initialization
 	{$$ = new structure_element_initialization_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| structure_element_name constant
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "':=' missing in structure element initialization.");
+	}
+| structure_element_name enumerated_value
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "':=' missing in enumerated structure element initialization.");
+	}
+| structure_element_name array_initialization
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "':=' missing in array structure element initialization.");
+	}
+| structure_element_name structure_initialization
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "':=' missing in structured structure element initialization.");
+	}
+/* ERROR_CHECK_END */
 ;
 /* NOTE: in order to remove a reduce/reduce conflict,
 *       all occurences of string_type_name
 *       have been replaced with identifier!
 | VAR_INPUT RETAIN     input_declaration_list END_VAR
 	{$$ = new input_declarations_c(new retain_option_c(locloc(@2)), $3, locloc(@$));}
 | VAR_INPUT NON_RETAIN input_declaration_list END_VAR
 	{$$ = new input_declarations_c(new non_retain_option_c(locloc(@2)), $3, locloc(@$));}
 /* ERROR_CHECK_BEGIN */
+| VAR_INPUT END_VAR
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no variable declared in input variable(s) declaration.");
+	}
+| VAR_INPUT RETAIN END_VAR
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@3), "no variable declared in retentive input variable(s) declaration.");
+	}
+| VAR_INPUT NON_RETAIN END_VAR
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@3), "no variable declared in non-retentive input variable(s) declaration.");
+	}
+| VAR_INPUT error input_declaration_list END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unexpected token after 'VAR_INPUT' in input variable(s) declaration.");
+	 yyerrok;
+	}
+| VAR_INPUT RETAIN error input_declaration_list END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "unexpected token after 'RETAIN' in retentive input variable(s) declaration.");
+	 yyerrok;
+	}
+| VAR_INPUT NON_RETAIN error input_declaration_list END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "unexpected token after 'NON_RETAIN' in non-retentive input variable(s) declaration.");
+	 yyerrok;
+	}
 | VAR_INPUT error END_VAR
 	{$$ = NULL;
-	 print_err_msg(current_filename, locf(@1), locl(@3), "error in input variable(s) declaration.");
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unknown error in input variable(s) declaration.");
-	 /* yychar */
+	 yyerrok;
+	}
+| VAR_INPUT RETAIN error END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "unknown error in retentive input variable(s) declaration.");
+	 yyerrok;
+	}
+| VAR_INPUT NON_RETAIN error END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "unknown error in non-retentive input variable(s) declaration.");
 	 yyerrok;
 	}
 /* ERROR_CHECK_END */
 ;
 input_declaration_list:
 input_declaration ';'
 	{$$ = new input_declaration_list_c(locloc(@$)); $$->add_element($1);}
 | input_declaration_list input_declaration ';'
 	{$$ = $1; $$->add_element($2);}
+/* ERROR_CHECK_BEGIN */
+| input_declaration error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "';' missing at end of input variable declaration.");
+	 yyerrok;
+	}
+| input_declaration_list input_declaration error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "';' missing at end of input variable declaration.");
+	 yyerrok;
+	}
+| input_declaration_list ';'
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "unexpected ';' after input variable declaration.");
+	}
+/* ERROR_CHECK_END */
 ;
 input_declaration:
 var_init_decl
 edge_declaration:
 var1_list ':' BOOL R_EDGE
 	{$$ = new edge_declaration_c(new raising_edge_option_c(locloc(@3)), $1, locloc(@$));}
 | var1_list ':' BOOL F_EDGE
 	{$$ = new edge_declaration_c(new falling_edge_option_c(locloc(@3)), $1, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| var1_list BOOL R_EDGE
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "':' missing between variable list and specification.");
+	}
+| var1_list BOOL F_EDGE
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "':' missing between variable list and specification.");
+	}
+| var1_list ':' BOOL R_EDGE F_EDGE
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@4), locl(@4), "'R_EDGE' and 'F_EDGE' can't be present at the same time in edge declaration.");
+	}
+| var1_list ':' R_EDGE
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "'BOOL' missing in edge declaration.");
+	}
+| var1_list ':' F_EDGE
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "'BOOL' missing in edge declaration.");
+	}
+/* ERROR_CHECK_END */
 ;
 var_init_decl:
 var1_init_decl
 	{$$ = new var1_init_decl_c($1, $3, locloc(@$));}
 | var1_list ':' subrange_spec_init
 	{$$ = new var1_init_decl_c($1, $3, locloc(@$));}
 | var1_list ':' enumerated_spec_init
 	{$$ = new var1_init_decl_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| var1_list simple_spec_init
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "':' missing between variable list and simple specification.");
+	}
+| var1_list subrange_spec_init
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "':' missing between variable list and subrange specification.");
+	}
+| var1_list enumerated_spec_init
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "':' missing between variable list and enumerated specification.");
+	}
+| var1_list ':' identifier
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "unknown variable type defined in variable declaration.");
+	}
+| var1_list ':' error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "no specification defined in variable declaration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 var1_list:
 variable_name
 	}
 | var1_list ',' variable_name
 	{$$ = $1; $$->add_element($3);
 	 variable_name_symtable.insert($3, prev_declared_variable_name_token);
 	}
+/* ERROR_CHECK_BEGIN */
+| var1_list variable_name
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "',' missing in variable list.");
+	}
+| var1_list ',' error
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "unexpected ',' in variable declaration.");
+	}
+/* ERROR_CHECK_END */
 ;
 array_var_init_decl:
 var1_list ':' array_spec_init
 	{$$ = new array_var_init_decl_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| var1_list array_spec_init
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "':' missing between variable list and array specification.");
+	}
+/* ERROR_CHECK_END */
 ;
 structured_var_init_decl:
 var1_list ':' initialized_structure
 	{$$ = new structured_var_init_decl_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| var1_list initialized_structure
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "':' missing between variable list and structured specification.");
+	}
+/* ERROR_CHECK_END */
 ;
 /* NOTE: see notes above fb_name_list and var1_list
 *       for reason why ':' was removed from this rule!
 fb_name_list_with_colon function_block_type_name
 	{$$ = new fb_name_decl_c($1, $2, NULL, locloc(@$));}
 /*| fb_name_list ':' function_block_type_name ASSIGN structure_initialization */
 | fb_name_list_with_colon function_block_type_name ASSIGN structure_initialization
 	{$$ = new fb_name_decl_c($1, $2, $4, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| fb_name_list_with_colon ASSIGN structure_initialization
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "no function block type name defined in function block declaration with initialization.");
+	}
+| fb_name_list_with_colon function_block_type_name structure_initialization
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "':=' missing in function block declaration with initialization.");
+	}
+| fb_name_list_with_colon function_block_type_name ASSIGN error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid initialization in function block declaration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 /* NOTE: In order to remove a reduce/reduce conflict between
 | VAR_OUTPUT RETAIN var_init_decl_list END_VAR
 	{$$ = new output_declarations_c(new retain_option_c(locloc(@2)), $3, locloc(@$));}
 | VAR_OUTPUT NON_RETAIN var_init_decl_list END_VAR
 	{$$ = new output_declarations_c(new non_retain_option_c(locloc(@2)), $3, locloc(@$));}
 /* ERROR_CHECK_BEGIN */
+| VAR_OUTPUT END_VAR
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no variable declared in output variable(s) declaration.");
+	}
+| VAR_OUTPUT RETAIN END_VAR
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@3), "no variable declared in retentive output variable(s) declaration.");
+	}
+| VAR_OUTPUT NON_RETAIN END_VAR
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@3), "no variable declared in non-retentive output variable(s) declaration.");
+	}
+| VAR_OUTPUT error var_init_decl_list END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unexpected token after 'VAR_OUPUT' in output variable(s) declaration.");
+	 yyerrok;
+	}
+| VAR_OUTPUT RETAIN error var_init_decl_list END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "unexpected token after 'RETAIN' in retentive output variable(s) declaration.");
+	 yyerrok;
+	}
+| VAR_OUTPUT NON_RETAIN error var_init_decl_list END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "unexpected token after 'NON_RETAIN' in non-retentive output variable(s) declaration.");
+	 yyerrok;
+	}
 | VAR_OUTPUT error END_VAR
 	{$$ = NULL;
-	 print_err_msg(current_filename, locf(@1), locl(@3), "error in output variable(s) declaration.");
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unknown error in output variable(s) declaration.");
-	 /* yychar */
+	 yyerrok;
+	}
+| VAR_OUTPUT RETAIN error END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "unknown error in retentive output variable(s) declaration.");
+	 yyerrok;
+	}
+| VAR_OUTPUT NON_RETAIN error END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "unknown error in non-retentive output variable(s) declaration.");
 	 yyerrok;
 	}
 /* ERROR_CHECK_END */
 ;
 input_output_declarations:
 VAR_IN_OUT var_declaration_list END_VAR
 	{$$ = new input_output_declarations_c($2, locloc(@$));}
 /* ERROR_CHECK_BEGIN */
+| VAR_IN_OUT END_VAR
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no variable declared in in_out variable(s) declaration.");
+	}
 | VAR_IN_OUT error END_VAR
 	{$$ = NULL;
-	 print_err_msg(current_filename, locf(@1), locl(@3), "error in in_out variable(s) declaration.");
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unknown error in in_out variable(s) declaration.");
-	 /* yychar */
 	 yyerrok;
 	}
 /* ERROR_CHECK_END */
 ;
 var_declaration_list:
 var_declaration ';'
 	{$$ = new var_declaration_list_c(locloc(@$)); $$->add_element($1);}
 | var_declaration_list var_declaration ';'
 	{$$ = $1; $$->add_element($2);}
+/* ERROR_CHECK_BEGIN */
+| var_declaration error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "';' missing at end of variable declaration.");
+	 yyerrok;
+	}
+| var_declaration_list var_declaration error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "';' missing at end of variable declaration.");
+	 yyerrok;
+	}
+| var_declaration_list ';'
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "unexpected ';' after variable declaration.");
+	}
+/* ERROR_CHECK_END */
 ;
 var_declaration:
 temp_var_decl
 	{$$ = new var1_init_decl_c($1, $3, locloc(@$));}
 | var1_list  ':' subrange_specification
 	{$$ = new var1_init_decl_c($1, $3, locloc(@$));}
 | var1_list  ':' enumerated_specification
 	{$$ = new var1_init_decl_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| var1_list simple_specification
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "':' missing between variable list and simple specification.");
+	}
+| var1_list subrange_specification
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "':' missing between variable list and subrange specification.");
+	}
+| var1_list enumerated_specification
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "':' missing between variable list and enumerated specification.");
+	}
+/* ERROR_CHECK_END */
 ;
 array_var_declaration:
 var1_list ':' array_specification
 	{$$ = new array_var_declaration_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| var1_list array_specification
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "':' missing between variable list and array specification.");
+	}
+/* ERROR_CHECK_END */
 ;
 structured_var_declaration:
 var1_list ':' prev_declared_structure_type_name
 	{$$ = new structured_var_declaration_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| var1_list prev_declared_structure_type_name
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "':' missing between variable list and structured specification.");
+	}
+| var1_list ':' identifier
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "unknown type name in structured variable declaration.");
+	}
+/* ERROR_CHECK_END */
 ;
 var_declarations:
 VAR var_init_decl_list END_VAR
 	{$$ = new var_declarations_c(NULL, $2, locloc(@$));}
 | VAR CONSTANT var_init_decl_list END_VAR
 	{$$ = new var_declarations_c(new constant_option_c(locloc(@2)), $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| VAR END_VAR
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no variable declared in variable(s) declaration.");
+	}
+| VAR CONSTANT END_VAR
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@3), "no variable declared in constant variable(s) declaration.");
+	}
+| VAR error var_init_decl_list END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unexpected token after 'VAR' in variable(s) declaration.");
+	 yyerrok;
+	}
+| VAR CONSTANT error var_init_decl_list END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "unexpected token after 'CONSTANT' in constant variable(s) declaration.");
+	 yyerrok;
+	}
+| VAR error END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unknown error in variable(s) declaration.");
+	 yyerrok;
+	}
+| VAR CONSTANT error END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unknown error in constant variable(s) declaration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 retentive_var_declarations:
 VAR RETAIN var_init_decl_list END_VAR
 	{$$ = new retentive_var_declarations_c($3, locloc(@$));}
 /* ERROR_CHECK_BEGIN */
+| VAR RETAIN END_VAR
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@3), "no variable declared in retentive variable(s) declaration.");
+	}
+| VAR RETAIN error var_init_decl_list END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "unexpected token after 'RETAIN' in retentive variable(s) declaration.");
+	 yyerrok;
+	}
 | VAR RETAIN error END_VAR
 	{$$ = NULL;
-	 print_err_msg(current_filename, locf(@1), locl(@3), "error in variable(s) declaration.");
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unknown error in retentive variable(s) declaration.");
-	 /* yychar */
 	 yyerrok;
 	}
 /* ERROR_CHECK_END */
 ;
 located_var_declarations:
-VAR  located_var_decl_list END_VAR
+VAR located_var_decl_list END_VAR
 	{$$ = new located_var_declarations_c(NULL, $2, locloc(@$));}
 | VAR CONSTANT located_var_decl_list END_VAR
 	{$$ = new located_var_declarations_c(new constant_option_c(locloc(@2)), $3, locloc(@$));}
 | VAR RETAIN located_var_decl_list END_VAR
 	{$$ = new located_var_declarations_c(new retain_option_c(locloc(@2)), $3, locloc(@$));}
 | VAR NON_RETAIN located_var_decl_list END_VAR
 	{$$ = new located_var_declarations_c(new non_retain_option_c(locloc(@2)), $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| VAR NON_RETAIN END_VAR
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@3), "no variable declared in non-retentive located variable(s) declaration.");
+	}
+| VAR error located_var_decl_list END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unexpected token after 'VAR' in located variable(s) declaration.");
+	 yyerrok;
+	}
+| VAR CONSTANT error located_var_decl_list END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "unexpected token after 'CONSTANT' in constant located variable(s) declaration.");
+	 yyerrok;
+	}
+| VAR RETAIN error located_var_decl_list END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "unexpected token after 'RETAIN' in retentive located variable(s) declaration.");
+	 yyerrok;
+	}
+| VAR NON_RETAIN error located_var_decl_list END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "unexpected token after 'NON_RETAIN' in non-retentive located variable(s) declaration.");
+	 yyerrok;
+	}
+| VAR NON_RETAIN error END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unknown error in non retentive variable(s) declaration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 /* helper symbol for located_var_declarations */
 located_var_decl_list:
 located_var_decl ';'
 	{$$ = new located_var_decl_list_c(locloc(@$)); $$->add_element($1);}
 | located_var_decl_list located_var_decl ';'
 	{$$ = $1; $$->add_element($2);}
+/* ERROR_CHECK_BEGIN */
+| located_var_decl error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "';' missing at end of located variable declaration.");
+	 yyerrok;
+	}
+| located_var_decl_list located_var_decl error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "';' missing at end of located variable declaration.");
+	 yyerrok;
+	}
+| located_var_decl_list ';'
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "unexpected ';' after located variable declaration.");
+	}
+/* ERROR_CHECK_END */
 ;
 located_var_decl:
 variable_name location ':' located_var_spec_init
 	{$$ = new located_var_decl_c($1, $2, $4, locloc(@$));
 	 variable_name_symtable.insert($1, prev_declared_variable_name_token);
 	}
 | location ':' located_var_spec_init
 	{$$ = new located_var_decl_c(NULL, $1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| variable_name location located_var_spec_init
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "':' missing between located variable location and specification.");
+	}
+| location located_var_spec_init
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "':' missing between located variable location and specification.");
+	}
+| variable_name location ':' error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "no specification defined in located variable declaration.");
+	 yyerrok;
+	}
+| location ':' error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "no specification defined in located variable declaration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 VAR_EXTERNAL external_declaration_list END_VAR
 	{$$ = new external_var_declarations_c(NULL, $2, locloc(@$));}
 | VAR_EXTERNAL CONSTANT external_declaration_list END_VAR
 	{$$ = new external_var_declarations_c(new constant_option_c(locloc(@2)), $3, locloc(@$));}
 /* ERROR_CHECK_BEGIN */
+| VAR_EXTERNAL END_VAR
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no variable declared in external variable(s) declaration.");
+	}
+| VAR_EXTERNAL CONSTANT END_VAR
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "no variable declared in constant external variable(s) declaration.");
+	}
+| VAR_EXTERNAL error external_declaration_list END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@4), "unexpected token after 'VAR_EXTERNAL' in external variable(s) declaration.");
+	 yyerrok;
+	}
+| VAR_EXTERNAL CONSTANT error external_declaration_list END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@5), "unexpected token after 'CONSTANT' in constant external variable(s) declaration.");
+	 yyerrok;
+	}
 | VAR_EXTERNAL error END_VAR
 	{$$ = NULL;
-	 print_err_msg(current_filename, locf(@1), locl(@3), "error in external variable(s) declaration.");
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unknown error in external variable(s) declaration.");
-	 /* yychar */
+	 yyerrok;
+	}
+| VAR_EXTERNAL CONSTANT error END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "unknown error in constant external variable(s) declaration.");
 	 yyerrok;
 	}
 /* ERROR_CHECK_END */
 ;
 /* helper symbol for external_var_declarations */
 external_declaration_list:
 external_declaration ';'
 	{$$ = new external_declaration_list_c(locloc(@$)); $$->add_element($1);}
-| external_declaration_list external_declaration';'
+| external_declaration_list external_declaration ';'
 	{$$ = $1; $$->add_element($2);}
+/* ERROR_CHECK_BEGIN */
+| external_declaration error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "';' missing at end of external variable declaration.");
+	 yyerrok;
+	}
+| external_declaration_list external_declaration error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "';' missing at end of external variable declaration.");
+	 yyerrok;
+	}
+| external_declaration_list ';'
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "unexpected ';' after external variable declaration.");
+	}
+/* ERROR_CHECK_END */
 ;
 external_declaration:
 global_var_name ':' simple_specification
 	}
 | global_var_name ':' function_block_type_name
 	{$$ = new external_declaration_c($1, $3, locloc(@$));
 	 variable_name_symtable.insert($1, prev_declared_fb_name_token);
 	}
+/* ERROR_CHECK_BEGIN */
+| global_var_name simple_specification
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "':' missing between external variable name and simple specification.");
+	}
+| global_var_name subrange_specification
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "':' missing between external variable name and subrange specification.");
+	}
+| global_var_name enumerated_specification
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "':' missing between external variable name and enumerated specification.");
+	}
+| global_var_name array_specification
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "':' missing between external variable name and array specification.");
+	}
+| global_var_name prev_declared_structure_type_name
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "':' missing between external variable name and structured specification.");
+	}
+| global_var_name function_block_type_name
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "':' missing between external variable name and function block type specification.");
+	}
+| global_var_name ':' identifier
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "unknown type name in external variable declaration.");
+	}
+| global_var_name ':' error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "no specification defined in external variable declaration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 global_var_name: identifier;
 | VAR_GLOBAL CONSTANT global_var_decl_list END_VAR
 	{$$ = new global_var_declarations_c(new constant_option_c(locloc(@2)), $3, locloc(@$));}
 | VAR_GLOBAL RETAIN global_var_decl_list END_VAR
 	{$$ = new global_var_declarations_c(new retain_option_c(locloc(@2)), $3, locloc(@$));}
 /* ERROR_CHECK_BEGIN */
+| VAR_GLOBAL END_VAR
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no variable declared in global variable(s) declaration.");
+	}
+| VAR_GLOBAL CONSTANT END_VAR
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@3), "no variable declared in constant global variable(s) declaration.");
+	}
+| VAR_GLOBAL RETAIN END_VAR
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@3), "no variable declared in retentive global variable(s) declaration.");
+	}
+| VAR_GLOBAL error global_var_decl_list END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unexpected token after 'VAR_GLOBAL' in global variable(s) declaration.");
+	 yyerrok;
+	}
+| VAR_GLOBAL CONSTANT error global_var_decl_list END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "unexpected token after 'CONSTANT' in constant global variable(s) declaration.");
+	 yyerrok;
+	}
+| VAR_GLOBAL RETAIN error global_var_decl_list END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "unexpected token after 'RETAIN' in retentive global variable(s) declaration.");
+	 yyerrok;
+	}
 | VAR_GLOBAL error END_VAR
 	{$$ = NULL;
-	 print_err_msg(current_filename, locf(@1), locl(@3), "error in global variable(s) declaration.");
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unknown error in global variable(s) declaration.");
-	 /* yychar */
+	 yyerrok;
+	}
+| VAR_GLOBAL CONSTANT error END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "unknown error in constant global variable(s) declaration.");
+	 yyerrok;
+	}
+| VAR_GLOBAL RETAIN error END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "unknown error in constant global variable(s) declaration.");
 	 yyerrok;
 	}
 /* ERROR_CHECK_END */
 ;
 global_var_decl_list:
 global_var_decl ';'
 	{$$ = new global_var_decl_list_c(locloc(@$)); $$->add_element($1);}
 | global_var_decl_list global_var_decl ';'
 	{$$ = $1; $$->add_element($2);}
+/* ERROR_CHECK_BEGIN */
+| global_var_decl error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "';' missing at end of global variable declaration.");
+	 yyerrok;
+	}
+| global_var_decl_list global_var_decl error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "';' missing at end of global variable declaration.");
+	 yyerrok;
+	}
+| global_var_decl_list ';'
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "unexpected ';' after global variable declaration.");
+	}
+/* ERROR_CHECK_END */
 ;
 global_var_decl:
+/* NOTE : This possibility defined in standard has no sense and generate a conflict (disabled)
 global_var_spec ':'
 	{$$ = new global_var_decl_c($1, NULL, locloc(@$));}
-| global_var_spec ':' located_var_spec_init
+*/
+global_var_spec ':' located_var_spec_init
 	{$$ = new global_var_decl_c($1, $3, locloc(@$));}
 | global_var_spec ':' function_block_type_name
 	{$$ = new global_var_decl_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| global_var_list located_var_spec_init
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "':' missing between global variable list and type specification.");
+	}
+| global_var_name location located_var_spec_init
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@3), locl(@3), "':' missing between global variable specification and type specification.");
+	}
+| global_var_spec function_block_type_name
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "':' missing between global variable specification and function block type specification.");
+	}
+| global_var_spec ':' identifier
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@3), locl(@3), "unknown variable type defined in global variable declaration.");
+	}
+| global_var_spec ':' error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "no specification defined in global variable declaration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 global_var_spec:
 global_var_list	{$$ = $1;}
 	{$$ = new global_var_spec_c(NULL, $1, locloc(@$));}
 | global_var_name location
 	{$$ = new global_var_spec_c($1, $2, locloc(@$));
 	 variable_name_symtable.insert($1, prev_declared_global_var_name_token);
 	}
 ;
 located_var_spec_init:
 simple_spec_init
 location:
 AT direct_variable
 	{$$ = new location_c($2, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| AT error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "invalid location in location declaration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 global_var_list:
 	}
 | global_var_list ',' global_var_name
 	{$$ = $1; $$->add_element($3);
 	 variable_name_symtable.insert($3, prev_declared_global_var_name_token);
 	}
+/* ERROR_CHECK_BEGIN */
+| global_var_list global_var_name
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "',' missing in global variable list.");
+	}
+| global_var_list ',' error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "unexpected ',' in global variable declaration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 string_var_declaration:
 ;
 single_byte_string_var_declaration:
 var1_list ':' single_byte_string_spec
 	{$$ = new single_byte_string_var_declaration_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| var1_list single_byte_string_spec
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "':' missing between variable list and string type specification.");
+	}
+/* ERROR_CHECK_END */
 ;
 /* NOTE: The constructs
 *
 *       [W]STRING
 | STRING ASSIGN single_byte_character_string
 	{$$ = new single_byte_string_spec_c(NULL, $3, locloc(@$));}
 */
 | STRING '[' integer ']' ASSIGN single_byte_character_string
 	{$$ = new single_byte_string_spec_c($3, $6, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| STRING '[' error ']'
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "invalid length value for limited string type specification.");
+	 yyerrok;
+	}
+| STRING '[' error ']' ASSIGN single_byte_character_string
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "invalid length value for limited string type specification.");
+	 yyerrok;
+	}
+| STRING '[' ']'
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@3), "missing length value for limited string type specification.");
+	}
+| STRING '[' ']' ASSIGN single_byte_character_string
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@3), "missing length value for limited string type specification.");
+	}
+| STRING '[' integer error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@3), locl(@3), "expecting ']' after length definition for limited string type specification.");
+	 yyerrok;
+	}
+| STRING '[' integer error ASSIGN single_byte_character_string
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@3), locl(@5), "expecting ']' after length definition for limited string type specification.");
+	 yyerrok;
+	}
+| STRING '[' integer ']' single_byte_character_string
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@4), locl(@5), "':=' missing before limited string type initialization.");
+	}
+| STRING '[' integer ']' ASSIGN error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@5), locl(@5), "invalid value for limited string type initialization.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 double_byte_string_var_declaration:
 var1_list ':' double_byte_string_spec
 	{$$ = new double_byte_string_var_declaration_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| var1_list double_byte_string_spec
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "':' missing between variable list and double byte string type specification.");
+	}
+/* ERROR_CHECK_END */
 ;
 double_byte_string_spec:
 /*  WSTRING
 	{$$ = new double_byte_string_spec_c(NULL, NULL, locloc(@$));}
 | WSTRING ASSIGN double_byte_character_string
 	{$$ = new double_byte_string_spec_c(NULL, $3, locloc(@$));}
 */
 | WSTRING '[' integer ']' ASSIGN double_byte_character_string
 	{$$ = new double_byte_string_spec_c($3, $6, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| WSTRING '[' error ']'
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "invalid length value for limited double byte string type specification.");
+	 yyerrok;
+	}
+| WSTRING '[' error ']' ASSIGN single_byte_character_string
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "invalid length value for limited double byte string type specification.");
+	 yyerrok;
+	}
+| WSTRING '[' ']'
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@3), "missing length value for limited double byte string type specification.");
+	}
+| WSTRING '[' ']' ASSIGN single_byte_character_string
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@3), "missing length value for limited double byte string type specification.");
+	}
+| WSTRING '[' integer error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@3), locl(@3), "expecting ']' after length definition for limited double byte string type specification.");
+	 yyerrok;
+	}
+| WSTRING '[' integer error ASSIGN single_byte_character_string
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@3), locl(@5), "expecting ']' after length definition for limited double byte string type specification.");
+	 yyerrok;
+	}
+| WSTRING '[' integer ']' single_byte_character_string
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@4), locl(@5), "':=' missing before limited double byte string type initialization.");
+	}
+| WSTRING '[' integer ']' ASSIGN error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@5), locl(@5), "invalid value for limited double byte string type initialization.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 incompl_located_var_declarations:
 	{$$ = new incompl_located_var_declarations_c(NULL, $2, locloc(@$));}
 | VAR     RETAIN incompl_located_var_decl_list END_VAR
 	{$$ = new incompl_located_var_declarations_c(new retain_option_c(locloc(@2)), $3, locloc(@$));}
 | VAR NON_RETAIN incompl_located_var_decl_list END_VAR
 	{$$ = new incompl_located_var_declarations_c(new non_retain_option_c(locloc(@2)), $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| VAR error incompl_located_var_decl_list END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unexpected token after 'VAR' in incomplete located variable(s) declaration.");
+	 yyerrok;
+	}
+| VAR RETAIN error incompl_located_var_decl_list END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "unexpected token after 'RETAIN' in retentive located variable(s) declaration.");
+	 yyerrok;
+	}
+| VAR NON_RETAIN error incompl_located_var_decl_list END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "unexpected token after 'NON_RETAIN' in non-retentive located variable(s) declaration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 /* helper symbol for incompl_located_var_declarations */
 incompl_located_var_decl_list:
 incompl_located_var_decl ';'
 	{$$ = new incompl_located_var_decl_list_c(locloc(@$)); $$->add_element($1);}
 | incompl_located_var_decl_list incompl_located_var_decl ';'
 	{$$ = $1; $$->add_element($2);}
+/* ERROR_CHECK_BEGIN */
+| incompl_located_var_decl error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "';' missing at end of incomplete located variable declaration.");
+	 yyerrok;
+	}
+| incompl_located_var_decl_list incompl_located_var_decl error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "';' missing at end of incomplete located variable declaration.");
+	 yyerrok;
+	}
+| incompl_located_var_decl_list ';'
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "unexpected ';' after incomplete located variable declaration.");
+	}
+/* ERROR_CHECK_END */
 ;
 incompl_located_var_decl:
 variable_name incompl_location ':' var_spec
 	{$$ = new incompl_located_var_decl_c($1, $2, $4, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| variable_name incompl_location ':' error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "no specification defined in incomplete located variable declaration.");
+	 yyerrok;
+	}
+| variable_name incompl_location var_spec
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "':' missing between incomplete located variable and type specification.");
+	}
+/* ERROR_CHECK_END */
 ;
 incompl_location:
 AT incompl_location_token
 var_init_decl_list:
 var_init_decl ';'
 	{$$ = new var_init_decl_list_c(locloc(@$)); $$->add_element($1);}
 | var_init_decl_list var_init_decl ';'
 	{$$ = $1; $$->add_element($2);}
+/* ERROR_CHECK_BEGIN */
+| var_init_decl_list var_init_decl error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "';' missing at end of variable declaration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 	 } else {
 	   library_element_symtable.insert($1, prev_declared_derived_function_name_token);
 	 }
 	}
 /* ERROR_CHECK_BEGIN */
-| FUNCTION error END_FUNCTION
+| function_name_declaration elementary_type_name io_OR_function_var_declarations_list function_body END_FUNCTION
 	{$$ = NULL;
-	 print_err_msg(current_filename, locf(@1), locl(@3), "error in function declaration.");
+	 yynerrs++;
-	 /* yychar */
+	 print_err_msg(current_filename, locf(@1), locl(@2), "':' missing after function name in function declaration.");
+	}
+| function_name_declaration derived_type_name io_OR_function_var_declarations_list function_body END_FUNCTION
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "':' missing after function name in function declaration.");
+	}
+| function_name_declaration error derived_type_name io_OR_function_var_declarations_list function_body END_FUNCTION
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "expecting ':' after function name in function declaration.");
+	 yyerrok;
+	}
+| function_name_declaration ':' io_OR_function_var_declarations_list function_body END_FUNCTION
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@3), "no return type defined in function declaration.");
+	}
+| function_name_declaration ':' error io_OR_function_var_declarations_list function_body END_FUNCTION
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "invalid return type defined in function declaration.");
+	 yyerrok;
+	}
+| function_name_declaration ':' identifier io_OR_function_var_declarations_list function_body END_FUNCTION
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "unknown return type defined in function declaration.");
+	}
+| function_name_declaration ':' elementary_type_name function_body END_FUNCTION
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@3), locl(@4), "no variable(s) declared in function declaration.");
+	}
+| function_name_declaration ':' derived_type_name function_body END_FUNCTION
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@3), locl(@4), "no variable(s) declared in function declaration.");
+	}
+| function_name_declaration ':' elementary_type_name io_OR_function_var_declarations_list END_FUNCTION
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@4), locl(@5), "no body defined in function declaration.");
+	}
+| function_name_declaration ':' derived_type_name io_OR_function_var_declarations_list END_FUNCTION
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@4), locl(@5), "no body defined in function declaration.");
+	}
+| function_name_declaration ':' elementary_type_name END_FUNCTION
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@3), locl(@4), "no variable(s) declared and body defined in function declaration.");
+	}
+| function_name_declaration ':' derived_type_name END_FUNCTION
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@3), locl(@4), "no variable(s) declared and body defined in function declaration.");
+	}
+| function_name_declaration error END_FUNCTION
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unknown error in function declaration.");
 	 yyerrok;
 	}
 /* ERROR_CHECK_END */
 ;
 	  * is cleared once the end of the function
 	  * is parsed.
 	  */
 	 variable_name_symtable.insert($2, prev_declared_variable_name_token);
 	}
+/* ERROR_CHECK_BEGIN */
+| FUNCTION error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "no function name defined in function declaration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 /* intermediate helper symbol for function_declaration */
 io_OR_function_var_declarations_list:
-/* empty */
+io_var_declarations
-	{$$ = new var_declarations_list_c(locloc(@$));}
+{$$ = new var_declarations_list_c(locloc(@1));$$->add_element($1);}
+| function_var_decls
+	{$$ = new var_declarations_list_c(locloc(@1));$$->add_element($1);}
 | io_OR_function_var_declarations_list io_var_declarations
 	{$$ = $1; $$->add_element($2);}
 | io_OR_function_var_declarations_list function_var_decls
 	{$$ = $1; $$->add_element($2);}
+/* ERROR_CHECK_BEGIN */
+| io_OR_function_var_declarations_list error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "unexpected token after variable(s) declaration in function declaration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 io_var_declarations:
 input_declarations
 function_var_decls:
 VAR CONSTANT var2_init_decl_list END_VAR
 	{$$ = new function_var_decls_c(new constant_option_c(locloc(@2)), $3, locloc(@$));}
 | VAR var2_init_decl_list END_VAR
 	{$$ = new function_var_decls_c(NULL, $2, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| VAR error var_init_decl_list END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unexpected token after 'VAR' in function variable(s) declaration.");
+	 yyerrok;
+	}
+| VAR CONSTANT error var_init_decl_list END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "unexpected token after 'CONSTANT' in constant function variable(s) declaration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 /* intermediate helper symbol for function_var_decls */
 var2_init_decl_list:
 var2_init_decl ';'
 	{$$ = new var2_init_decl_list_c(locloc(@$)); $$->add_element($1);}
 | var2_init_decl_list var2_init_decl ';'
 	{$$ = $1; $$->add_element($2);}
+/* ERROR_CHECK_BEGIN */
+| var2_init_decl error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "';' missing at end of function variable(s) declaration.");
+	 yyerrok;
+	}
+| var2_init_decl_list var2_init_decl error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "';' missing at end of function variable(s) declaration.");
+	 yyerrok;
+	}
+| var2_init_decl_list ';'
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "unexpected ';' after function variable(s) declaration.");
+	}
+/* ERROR_CHECK_END */
 ;
 function_body:
 statement_list	{$$ = $1;} /* if we leave it for the default action we get a type clash! */
 	  * are no longer valid!
 	  */
 	 variable_name_symtable.pop();
 	}
 /* ERROR_CHECK_BEGIN */
+| FUNCTION_BLOCK io_OR_other_var_declarations_list function_block_body END_FUNCTION_BLOCK
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no function block name defined in function block declaration.");
+	}
+| FUNCTION_BLOCK error io_OR_other_var_declarations_list function_block_body END_FUNCTION_BLOCK
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "invalid function block name in function block declaration.");
+	 yyerrok;
+	}
+| FUNCTION_BLOCK derived_function_block_name function_block_body END_FUNCTION_BLOCK
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@3), "no variable(s) declared in function declaration.");
+	}
+| FUNCTION_BLOCK derived_function_block_name io_OR_other_var_declarations_list END_FUNCTION_BLOCK
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@3), locl(@4), "no body defined in function block declaration.");
+	}
+| FUNCTION_BLOCK derived_function_block_name END_FUNCTION_BLOCK
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@3), "no variable(s) declared and body defined in function block declaration.");
+	}
 | FUNCTION_BLOCK error END_FUNCTION_BLOCK
 	{$$ = NULL;
-	 print_err_msg(current_filename, locf(@1), locl(@3), "error in function block declaration.");
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unknown error in function block declaration.");
-	 /* yychar */
 	 yyerrok;
 	}
 /* ERROR_CHECK_END */
 ;
 /*  { io_var_declarations | other_var_declarations }   */
 /*
 * NOTE: we re-use the var_declarations_list_c
 */
 io_OR_other_var_declarations_list:
-/* empty */
+io_var_declarations
-	{$$ = new var_declarations_list_c(locloc(@$));}
+{$$ = new var_declarations_list_c(locloc(@$));$$->add_element($1);}
+| other_var_declarations
+{$$ = new var_declarations_list_c(locloc(@$));$$->add_element($1);}
 | io_OR_other_var_declarations_list io_var_declarations
 	{$$ = $1; $$->add_element($2);}
 | io_OR_other_var_declarations_list other_var_declarations
 	{$$ = $1; $$->add_element($2);}
+/* ERROR_CHECK_BEGIN */
+| io_OR_other_var_declarations_list error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "unexpected token after variable(s) declaration in function declaration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 /* NOTE:
 *  The IEC specification gives the following definition:
 *  other_var_declarations ::=
 | non_retentive_var_decls
 | external_var_declarations
 | var_declarations
 | retentive_var_declarations
 | incompl_located_var_declarations
-/* TODO: the following error rule is not working! Must be fixed. */
-/* ERROR_CHECK_BEGIN */
-| VAR error END_VAR
-	{$$ = NULL;
-	 print_err_msg(current_filename, locf(@1), locl(@3), "error in variable(s) declaration.");
-	 /* yychar */
-	 yyerrok;
-	}
-/* ERROR_CHECK_END */
 ;
 temp_var_decls:
 VAR_TEMP temp_var_decls_list END_VAR
 	{$$ = new temp_var_decls_c($2, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| VAR_TEMP END_VAR
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no variable declared in temporary variable(s) declaration.");
+	}
+| VAR_TEMP error temp_var_decls_list END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unexpected token after 'VAR_TEMP' in function variable(s) declaration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 /* intermediate helper symbol for temp_var_decls */
 temp_var_decls_list:
 temp_var_decl ';'
 	{$$ = new temp_var_decls_list_c(locloc(@$)); $$->add_element($1);}
 | temp_var_decls_list temp_var_decl ';'
 	{$$ = $1; $$->add_element($2);}
+/* ERROR_CHECK_BEGIN */
+| temp_var_decl error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "';' missing at end of temporary variable declaration.");
+	 yyerrok;
+	}
+| temp_var_decls_list temp_var_decl error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "';' missing at end of temporary variable declaration.");
+	 yyerrok;
+	}
+| temp_var_decls_list ';'
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "unexpected ';' after temporary variable declaration.");
+	}
+/* ERROR_CHECK_END */
 ;
 non_retentive_var_decls:
 VAR NON_RETAIN var_init_decl_list END_VAR
 	{$$ = new non_retentive_var_decls_c($3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| VAR NON_RETAIN error var_init_decl_list END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "unexpected token after 'NON_RETAIN' in non-retentive temporary variable(s) declaration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 function_block_body:
 	  * are no longer valid!
 	  */
 	 variable_name_symtable.pop();
 	}
 /* ERROR_CHECK_BEGIN */
+| PROGRAM program_var_declarations_list function_block_body END_PROGRAM
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no program name defined in program declaration.");
+	}
+| PROGRAM error program_var_declarations_list function_block_body END_PROGRAM
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "invalid program name in program declaration.");
+	 yyerrok;
+	}
+| PROGRAM program_type_name function_block_body END_PROGRAM
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@3), "no variable(s) declared in program declaration.");
+	}
+| PROGRAM program_type_name program_var_declarations_list END_PROGRAM
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@3), locl(@4), "no body defined in program declaration.");
+	}
+| PROGRAM program_type_name END_PROGRAM
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@3), "no variable(s) declared and body defined in program declaration.");
+	}
 | PROGRAM error END_PROGRAM
 	{$$ = NULL;
-	 print_err_msg(current_filename, locf(@1), locl(@3), "error in function block declaration.");
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unknown error in program declaration.");
-	 /* yychar */
 	 yyerrok;
 	}
 /* ERROR_CHECK_END */
 ;
 /* helper symbol for program_declaration */
 /*
 * NOTE: we re-use the var_declarations_list_c
 */
 program_var_declarations_list:
-/* empty */
+io_var_declarations
-	{$$ = new var_declarations_list_c(locloc(@$));}
+	{$$ = new var_declarations_list_c(locloc(@$)); $$->add_element($1);}
+| other_var_declarations
+	{$$ = new var_declarations_list_c(locloc(@$)); $$->add_element($1);}
+| located_var_declarations
+	{$$ = new var_declarations_list_c(locloc(@$)); $$->add_element($1);}
 | program_var_declarations_list io_var_declarations
 	{$$ = $1; $$->add_element($2);}
 | program_var_declarations_list other_var_declarations
 	{$$ = $1; $$->add_element($2);}
 | program_var_declarations_list located_var_declarations
 	{$$ = $1; $$->add_element($2);}
 /*
 | program_var_declarations_list program_access_decls
 	{$$ = $1; $$->add_element($2);}
 */
+/* ERROR_CHECK_BEGIN */
+| program_var_declarations_list error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "unexpected token after variable(s) declaration in program declaration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 /* TODO ... */
 /*
 	{$$ = $1; $$->add_element($2);}
 | sfc_network transition
 	{$$ = $1; $$->add_element($2);}
 | sfc_network action
 	{$$ = $1; $$->add_element($2);}
+/* ERROR_CHECK_BEGIN */
+| sfc_network error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "unexpected token after SFC network in sequencial function chart.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 initial_step:
 INITIAL_STEP step_name ':' action_association_list END_STEP
 //  INITIAL_STEP identifier ':' action_association_list END_STEP
 	{$$ = new initial_step_c($2, $4, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| INITIAL_STEP ':' action_association_list END_STEP
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no step name defined in initial step declaration.");
+	}
+| INITIAL_STEP error ':' action_association_list END_STEP
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "invalid step name defined in initial step declaration.");
+	 yyerrok;
+	}
+| INITIAL_STEP step_name action_association_list END_STEP
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@3), "':' missing after step name in initial step declaration.");
+	}
+| INITIAL_STEP step_name error action_association_list END_STEP
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "expecting ':' after step name in initial step declaration.");
+	 yyerrok;
+	}
+| INITIAL_STEP step_name ':' error END_STEP
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "invalid action association list in initial step declaration.");
+	 yyerrok;
+	}
+| INITIAL_STEP error END_STEP
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unknown error in initial step declaration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 step:
 STEP step_name ':' action_association_list END_STEP
 //  STEP identifier ':' action_association_list END_STEP
 	{$$ = new step_c($2, $4, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| STEP ':' action_association_list END_STEP
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no step name defined in step declaration.");
+	}
+| STEP error ':' action_association_list END_STEP
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "invalid step name defined in step declaration.");
+	 yyerrok;
+	}
+| STEP step_name action_association_list END_STEP
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@3), "':' missing after step name in step declaration.");
+	}
+| STEP step_name error action_association_list END_STEP
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "expecting ':' after step name in step declaration.");
+	 yyerrok;
+	}
+| STEP step_name ':' error END_STEP
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "invalid action association list in step declaration.");
+	 yyerrok;
+	}
+| STEP error END_STEP
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unknown error in step declaration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 /* helper symbol for:
 *  - initial_step
 *  - step
 action_association_list:
 /* empty */
 	{$$ = new action_association_list_c(locloc(@$));}
 | action_association_list action_association ';'
 	{$$ = $1; $$->add_element($2);}
+/* ERROR_CHECK_BEGIN */
+| action_association_list action_association error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "';' missing at end of action association declaration.");
+	 yyerrok;
+	}
+| action_association_list ';'
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "unexpected ';' after action association declaration.");
+	}
+/* ERROR_CHECK_END */
 ;
 // step_name: identifier;
 step_name: any_identifier;
 action_association:
 action_name '(' {cmd_goto_sfc_qualifier_state()} action_qualifier {cmd_pop_state()} indicator_name_list ')'
 	{$$ = new action_association_c($1, $4, $6, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+/*| action_name '(' error indicator_name_list ')'
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "invalid qualifier defined in action association.");
+	 yyerrok;
+	}*/
+/* ERROR_CHECK_END */
 ;
 /* helper symbol for action_association */
 indicator_name_list:
 /* empty */
 	{$$ = new indicator_name_list_c(locloc(@$));}
 | indicator_name_list ',' indicator_name
 	{$$ = $1; $$->add_element($3);}
+/* ERROR_CHECK_BEGIN */
+| indicator_name_list indicator_name
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "',' missing at end of action association declaration.");
+	}
+| indicator_name_list ',' error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "unexpected token after ',' in indicator list.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 // action_name: identifier;
 action_name: any_identifier;
 	{$$ = NULL;}
 | qualifier
 	{$$ = new action_qualifier_c($1, NULL, locloc(@$));}
 | timed_qualifier ',' action_time
 	{$$ = new action_qualifier_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| timed_qualifier action_time
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "',' missing between timed qualifier and action time in action qualifier.");
+	}
+| timed_qualifier ',' error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "unexpected token after ',' in action qualifier.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 qualifier:
 N		{$$ = new qualifier_c(strdup("N"), locloc(@$));}
 | R		{$$ = new qualifier_c(strdup("R"), locloc(@$));}
 steps:
 step_name
 	{$$ = new steps_c($1, NULL, locloc(@$));}
 | '(' step_name_list ')'
 	{$$ = new steps_c(NULL, $2, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| '(' step_name_list error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "expecting ')' at the end of step list in transition declaration.");
+	 yyerrok;
+	}
+| '(' error ')'
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "invalid step list in transition declaration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 step_name_list:
 step_name ',' step_name
 	{$$ = new step_name_list_c(locloc(@$)); $$->add_element($1); $$->add_element($3);}
 | step_name_list ',' step_name
 	{$$ = $1; $$->add_element($3);}
+/* ERROR_CHECK_BEGIN */
+| step_name_list step_name
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "',' missing in step list.");
+	}
+| step_name_list ',' error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid step name in step list.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 /* NOTE: flex will automatically pop() out of body_state to previous state.
 *       We do not need to give a command from bison to return to previous flex state,
 *       after forcing flex to go to body_state.
 */
 transition:
-TRANSITION
+TRANSITION transition_priority
 FROM steps TO steps
 {cmd_goto_body_state();} transition_condition
 END_TRANSITION
-	{$$ = new transition_c(NULL, NULL, $3, $5, $7, locloc(@$));}
+	{$$ = new transition_c(NULL, $2, $4, $6, $8, locloc(@$));}
 //| TRANSITION identifier FROM steps TO steps ...
-| TRANSITION transition_name
+| TRANSITION transition_name transition_priority
 FROM steps TO steps
 {cmd_goto_body_state();} transition_condition
 END_TRANSITION
-	{$$ = new transition_c($2, NULL, $4, $6, $8, locloc(@$));}
+	{$$ = new transition_c($2, $3, $5, $7, $9, locloc(@$));}
-| TRANSITION '(' {cmd_goto_sfc_priority_state();} PRIORITY {cmd_pop_state();} ASSIGN integer ')'
+/* ERROR_CHECK_BEGIN */
-FROM steps TO steps
+| TRANSITION error transition_priority FROM steps TO steps {cmd_goto_body_state();} transition_condition END_TRANSITION
-{cmd_goto_body_state();} transition_condition
+	{$$ = NULL;
-END_TRANSITION
+	 print_err_msg(current_filename, locf(@1), locl(@3), "invalid transition name defined in transition declaration.");
-{$$ = new transition_c(NULL, $7, $10, $12, $14, locloc(@$));}
+	 yyerrok;
-//| TRANSITION identifier '(' PRIORITY ASSIGN integer ')' FROM steps TO steps ...
+	}
-| TRANSITION transition_name '(' {cmd_goto_sfc_priority_state();} PRIORITY {cmd_pop_state();} ASSIGN integer ')'
+| TRANSITION transition_name error FROM steps TO steps {cmd_goto_body_state();} transition_condition END_TRANSITION
-FROM steps TO steps
+	{$$ = NULL;
-{cmd_goto_body_state();} transition_condition
+	 print_err_msg(current_filename, locf(@1), locl(@3), "invalid transition priority defined in transition declaration.");
-END_TRANSITION
+	 yyerrok;
-{$$ = new transition_c($2, $8, $11, $13, $15, locloc(@$));}
+	}
-;
+| TRANSITION transition_priority FROM TO steps {cmd_goto_body_state();} transition_condition END_TRANSITION
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@3), locl(@4), "no origin step(s) defined in transition declaration.");
+	}
+| TRANSITION transition_name transition_priority FROM TO steps {cmd_goto_body_state();} transition_condition END_TRANSITION
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@4), locl(@5), "no origin step(s) defined in transition declaration.");
+	}
+| TRANSITION transition_priority FROM error TO steps {cmd_goto_body_state();} transition_condition END_TRANSITION
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@3), locl(@5), "invalid origin step(s) defined in transition declaration.");
+	 yyerrok;
+	}
+| TRANSITION transition_name transition_priority FROM error TO steps {cmd_goto_body_state();} transition_condition END_TRANSITION
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@4), locl(@6), "invalid origin step(s) defined in transition declaration.");
+	 yyerrok;
+	}
+| TRANSITION transition_priority FROM steps steps {cmd_goto_body_state();} transition_condition END_TRANSITION
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@4), locl(@5), "'TO' missing between origin step(s) and destination step(s) in transition declaration.");
+	}
+| TRANSITION transition_name transition_priority FROM steps steps {cmd_goto_body_state();} transition_condition END_TRANSITION
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@5), locl(@6), "'TO' missing between origin step(s) and destination step(s) in transition declaration.");
+	}
+| TRANSITION transition_priority FROM steps error steps {cmd_goto_body_state();} transition_condition END_TRANSITION
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@4), locl(@6), "expecting 'TO' between origin step(s) and destination step(s) in transition declaration.");
+	 yyerrok;
+	}
+| TRANSITION transition_name transition_priority FROM steps error steps {cmd_goto_body_state();} transition_condition END_TRANSITION
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@5), locl(@7), "expecting 'TO' between origin step(s) and destination step(s) in transition declaration.");
+	 yyerrok;
+	}
+| TRANSITION transition_priority FROM steps TO {cmd_goto_body_state();} transition_condition END_TRANSITION
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@5), locl(@7), "no destination step(s) defined in transition declaration.");
+	}
+| TRANSITION transition_name transition_priority FROM steps TO {cmd_goto_body_state();} transition_condition END_TRANSITION
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@6), locl(@8), "no destination step(s) defined in transition declaration.");
+	}
+| TRANSITION transition_priority FROM steps TO error {cmd_goto_body_state();} transition_condition END_TRANSITION
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@5), locl(@8), "invalid destination step(s) defined in transition declaration.");
+	 yyerrok;
+	}
+| TRANSITION transition_name transition_priority FROM steps TO error {cmd_goto_body_state();} transition_condition END_TRANSITION
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@6), locl(@9), "invalid destination step(s) defined in transition declaration.");
+	 yyerrok;
+	}
+| TRANSITION transition_priority {cmd_goto_body_state();} transition_condition END_TRANSITION
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "no origin and destination step(s) defined in transition declaration.");
+	}
+| TRANSITION transition_name transition_priority {cmd_goto_body_state();} transition_condition END_TRANSITION
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@3), locl(@5), "no origin and destination step(s) defined in transition declaration.");
+	}
+| TRANSITION error END_TRANSITION
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unknown error in transition declaration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
+;
+transition_priority:
+/* empty */
+{$$ = NULL;}
+| '(' {cmd_goto_sfc_priority_state();} PRIORITY {cmd_pop_state();} ASSIGN integer ')'
+	{$$ = $6;}
+;
 transition_condition:
 ':' eol_list simple_instr_list
 	{$$ = new transition_condition_c($3, NULL, locloc(@$));}
 | ASSIGN expression ';'
 	{$$ = new transition_condition_c(NULL, $2, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| eol_list simple_instr_list
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "':' missing before IL condition in transition declaration.");
+	}
+| ':' eol_list error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "no instructions defined in IL condition of transition declaration.");
+	 yyerrok;
+	}
+| ASSIGN ';'
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "no expression defined in ST condition of transition declaration.");
+	 yyerrok;
+	}
+| ASSIGN error ';'
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid expression defined in ST condition of transition declaration.");
+	 yyerrok;
+	}
+| ASSIGN expression error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "expecting ';' after expression defined in ST condition of transition declaration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 action:
 //  ACTION identifier ':' ...
 ACTION action_name ':' {cmd_goto_body_state();} function_block_body END_ACTION
 	{$$ = new action_c($2, $5, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| ACTION ':' {cmd_goto_body_state();} function_block_body END_ACTION
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no action name defined in action declaration.");
+	}
+| ACTION error ':' {cmd_goto_body_state();} function_block_body END_ACTION
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "invalid action name defined in action declaration.");
+	 yyerrok;
+	}
+| ACTION action_name {cmd_goto_body_state();} function_block_body END_ACTION
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "':' missing after action name in action declaration.");
+	}
+| ACTION action_name ':' END_ACTION
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@3), locl(@4), "no body defined in action declaration.");
+	 yyerrok;
+	}
+| ACTION error END_ACTION
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unknown error in action declaration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 /********************************/
 /* B 1.7 Configuration elements */
 * namespace for each of the name types (resource names, program names,
 * global varaiable names), i.e. letting the names be re-used across
 * each of the groups (resource, program, global variables), produces
 * reduce/reduce conflicts in the syntax parser. Actually, it is only
 * the resource names that need to be distinguished into a
-* prev_delcared_resource_name so as not to conflict with [gloabl] variable
+* prev_declared_resource_name so as not to conflict with [gloabl] variable
 * names in the 'data' construct.
 * The program names are only tracked to make sure that two programs do not
 * get the same name.
 *
 * Using a single namespace does have the drawback that the user will
 	{$$ = new configuration_declaration_c($2, $3, $4, $5, $6, locloc(@$));
 	 library_element_symtable.insert($2, prev_declared_configuration_name_token);
 	 variable_name_symtable.pop();
 }
 /* ERROR_CHECK_BEGIN */
+| CONFIGURATION
+optional_global_var_declarations
+single_resource_declaration
+{variable_name_symtable.pop();}
+optional_access_declarations
+optional_instance_specific_initializations
+END_CONFIGURATION
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no configuration name defined in configuration declaration.");
+	}
+| CONFIGURATION
+optional_global_var_declarations
+resource_declaration_list
+optional_access_declarations
+optional_instance_specific_initializations
+END_CONFIGURATION
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no configuration name defined in configuration declaration.");
+	}
+| CONFIGURATION error
+optional_global_var_declarations
+single_resource_declaration
+{variable_name_symtable.pop();}
+optional_access_declarations
+optional_instance_specific_initializations
+END_CONFIGURATION
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "invalid configuration name defined in configuration declaration.");
+	 yyerrok;
+	}
+| CONFIGURATION error
+optional_global_var_declarations
+resource_declaration_list
+optional_access_declarations
+optional_instance_specific_initializations
+END_CONFIGURATION
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "invalid configuration name defined in configuration declaration.");
+	 yyerrok;
+	}
+| CONFIGURATION configuration_name
+optional_global_var_declarations
+optional_access_declarations
+optional_instance_specific_initializations
+END_CONFIGURATION
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no resource(s) defined in configuration declaration.");
+	 yyerrok;
+	}
+| CONFIGURATION configuration_name
+optional_global_var_declarations
+error
+optional_access_declarations
+optional_instance_specific_initializations
+END_CONFIGURATION
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "invalid resource(s) defined in configuration declaration.");
+	 yyerrok;
+	}
 | CONFIGURATION error END_CONFIGURATION
 	{$$ = NULL;
-	 print_err_msg(current_filename, locf(@1), locl(@3), "error in configuration declaration.");
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unknown error in configuration declaration.");
-	 /* yychar */
 	 yyerrok;
 	}
 /* ERROR_CHECK_END */
 ;
 resource_declaration_list:
 resource_declaration
 	{$$ = new resource_declaration_list_c(locloc(@$)); $$->add_element($1);}
 | resource_declaration_list resource_declaration
 	{$$ = $1; $$->add_element($2);}
+/* ERROR_CHECK_BEGIN */
+| resource_declaration_list error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "unexpected token after resource declaration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 resource_declaration:
 RESOURCE {variable_name_symtable.push();} resource_name ON resource_type_name
 END_RESOURCE
 	{$$ = new resource_declaration_c($3, $5, $6, $7, locloc(@$));
 	 variable_name_symtable.pop();
 	 variable_name_symtable.insert($3, prev_declared_resource_name_token);
 	}
+/* ERROR_CHECK_BEGIN */
+| RESOURCE {variable_name_symtable.push();} ON resource_type_name
+optional_global_var_declarations
+single_resource_declaration
+END_RESOURCE
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "no resource name defined in resource declaration.");
+	}
+| RESOURCE error END_RESOURCE
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unknown error in resource declaration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 single_resource_declaration:
 task_configuration_list program_configuration_list
 task_configuration_list:
 // empty
 	{$$ = new task_configuration_list_c(locloc(@$));}
 | task_configuration_list task_configuration ';'
 	{$$ = $1; $$->add_element($2);}
+/* ERROR_CHECK_BEGIN */
+| task_configuration_list task_configuration error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "';' missing at the end of task configuration in resource declaration.");
+	 yyerrok;
+	}
+| task_configuration_list ';'
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "unexpected ';' after task configuration in resource declaration.");
+	}
+/* ERROR_CHECK_END */
 ;
 // helper symbol for single_resource_declaration //
 program_configuration_list:
 program_configuration ';'
 	{$$ = new program_configuration_list_c(locloc(@$)); $$->add_element($1);}
 | program_configuration_list program_configuration ';'
 	{$$ = $1; $$->add_element($2);}
+/* ERROR_CHECK_BEGIN */
+| program_configuration error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "';' missing at the end of program configuration in resource declaration.");
+	 yyerrok;
+	}
+| program_configuration_list program_configuration error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "';' missing at the end of program configuration in resource declaration.");
+	 yyerrok;
+	}
+| program_configuration_list ';'
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "unexpected ';' after program configuration in resource declaration.");
+	}
+/* ERROR_CHECK_END */
 ;
 resource_name: identifier;
 /*
 access_declarations:
 VAR_ACCESS access_declaration_list END_VAR
 	{$$ = NULL;}
+// ERROR_CHECK_BEGIN //
+| VAR_ACCESS END_VAR
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no variable declared in access variable(s) declaration.");
+	}
+| VAR_ACCESS error access_declaration_list END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unexpected token after 'VAR_ACCESS' in access variable(s) declaration.");
+	 yyerrok;
+	}
+| VAR_ACCESS error END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unknown error in access variable(s) declaration.");
+	 yyerrok;
+	}
+// ERROR_CHECK_END //
 ;
 // helper symbol for access_declarations //
 access_declaration_list:
 access_declaration ';'
 | access_declaration_list access_declaration ';'
+// ERROR_CHECK_BEGIN //
+| access_declaration error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "';' missing at the end of access variable declaration.");
+	 yyerrok;
+	}
+| access_declaration_list access_declaration error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "';' missing at the end of access variable declaration.");
+	 yyerrok;
+	}
+| access_declaration_list ';'
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "unexpected ';' after access variable declaration.");
+	}
+// ERROR_CHECK_END //
 ;
 access_declaration:
 access_name ':' access_path ':' non_generic_type_name
 ;
 access_path:
 direct_variable
-| prev_delcared_resource_name '.' direct_variable
+| prev_declared_resource_name '.' direct_variable
 | any_fb_name_list symbolic_variable
-| prev_delcared_resource_name '.' any_fb_name_list symbolic_variable
+| prev_declared_resource_name '.' any_fb_name_list symbolic_variable
-| prev_delcared_program_name '.'  any_fb_name_list symbolic_variable
+| prev_declared_program_name '.'  any_fb_name_list symbolic_variable
-| prev_delcared_resource_name '.' prev_delcared_program_name '.' any_fb_name_list symbolic_variable
+| prev_declared_resource_name '.' prev_declared_program_name '.' any_fb_name_list symbolic_variable
 ;
 */
 // helper symbol for
 //  - access_path
 */
 task_configuration:
 TASK task_name task_initialization
 	{$$ = new task_configuration_c($2, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| TASK task_initialization
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no task name defined in task declaration.");
+	}
+| TASK error task_initialization
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "invalid task name defined in task declaration.");
+	 yyerrok;
+	}
+| TASK task_name error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid task initialization in task declaration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 /* NOTE: The specification does not mention the namespace to which task names
 *       should belong to. Unlike resource and program names, for the moment we
 *       let the task names belong to their own private namespace, as they do not
 // [SINGLE ASSIGN data_source ',']
 /* empty */
 	{$$ = NULL;}
 | SINGLE ASSIGN {cmd_pop_state();} data_source ',' {cmd_goto_task_init_state();}
 	{$$ = $4;}
+/* ERROR_CHECK_BEGIN */
+| SINGLE {cmd_pop_state();} data_source ',' {cmd_goto_task_init_state();}
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "':=' missing after 'SINGLE' in task initialization.");
+	}
+| SINGLE error {cmd_pop_state();} data_source ',' {cmd_goto_task_init_state();}
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@4), "expecteing ':=' after 'SINGLE' in task initialization.");
+	 yyerrok;
+	}
+| SINGLE ASSIGN {cmd_pop_state();} ',' {cmd_goto_task_init_state();}
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "no data source defined in 'SINGLE' statement of task initialization.");
+	}
+| SINGLE ASSIGN {cmd_pop_state();} error ',' {cmd_goto_task_init_state();}
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@5), "invalid data source defined in 'SINGLE' statement of task initialization.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 task_initialization_interval:
 // [INTERVAL ASSIGN data_source ',']
 /* empty */
 	{$$ = NULL;}
 | INTERVAL ASSIGN {cmd_pop_state();} data_source ',' {cmd_goto_task_init_state();}
 	{$$ = $4;}
+/* ERROR_CHECK_BEGIN */
+| INTERVAL {cmd_pop_state();} data_source ',' {cmd_goto_task_init_state();}
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "':=' missing after 'INTERVAL' in task initialization.");
+	}
+| INTERVAL error {cmd_pop_state();} data_source ',' {cmd_goto_task_init_state();}
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@4), "expecting ':=' after 'INTERVAL' in task initialization.");
+	 yyerrok;
+	}
+| INTERVAL ASSIGN {cmd_pop_state();} ',' {cmd_goto_task_init_state();}
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "no data source defined in 'INTERVAL' statement of task initialization.");
+	}
+| INTERVAL ASSIGN {cmd_pop_state();} error ',' {cmd_goto_task_init_state();}
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@5), "invalid data source defined in 'INTERVAL' statement of task initialization.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 task_initialization_priority:
 // PRIORITY ASSIGN integer
 PRIORITY ASSIGN {cmd_pop_state();} integer
 	{$$ = $4;}
+/* ERROR_CHECK_BEGIN */
+| PRIORITY {cmd_pop_state();} integer
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "':=' missing after 'PRIORITY' in task initialization.");
+	}
+| PRIORITY error {cmd_pop_state();} integer
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@4), "expecting ':=' after 'PRIORITY' in task initialization.");
+	 yyerrok;
+	}
+| PRIORITY ASSIGN {cmd_pop_state();} error
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "no priority number defined in 'PRIORITY' statement of task initialization.");
+	}
+/* ERROR_CHECK_END */
 ;
 data_source:
 	}
 | PROGRAM NON_RETAIN program_name optional_task_name ':' prev_declared_program_type_name optional_prog_conf_elements
 	{$$ = new program_configuration_c(new non_retain_option_c(locloc(@2)), $3, $4, $6, $7, locloc(@$));
 	 variable_name_symtable.insert($3, prev_declared_program_name_token);
 	}
+/* ERROR_CHECK_BEGIN */
+| PROGRAM program_name optional_task_name ':' identifier optional_prog_conf_elements
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unknown program type name after ':' in program configuration.");
+	}
+| PROGRAM RETAIN program_name optional_task_name ':' identifier optional_prog_conf_elements
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "unknown program type name after ':' in program configuration.");
+	}
+| PROGRAM NON_RETAIN program_name optional_task_name ':' identifier optional_prog_conf_elements
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "unknown program type name after ':' in program configuration.");
+	}
+| PROGRAM error program_name optional_task_name ':' prev_declared_program_type_name optional_prog_conf_elements
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unexpected token after 'PROGRAM' in program configuration.");
+	 yyerrok;
+	}
+| PROGRAM RETAIN error program_name optional_task_name ':' prev_declared_program_type_name optional_prog_conf_elements
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "unexpected token after 'RETAIN' in retentive program configuration.");
+	 yyerrok;
+	}
+| PROGRAM NON_RETAIN error program_name optional_task_name ':' prev_declared_program_type_name optional_prog_conf_elements
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "unexpected token after 'NON_RETAIN' in non-retentive program configuration.");
+	 yyerrok;
+	}
+| PROGRAM optional_task_name ':' prev_declared_program_type_name optional_prog_conf_elements
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no program name defined in program configuration.");
+	}
+| PROGRAM RETAIN optional_task_name ':' prev_declared_program_type_name optional_prog_conf_elements
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@3), "no program name defined in retentive program configuration.");
+	}
+| PROGRAM NON_RETAIN optional_task_name ':' prev_declared_program_type_name optional_prog_conf_elements
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@3), "no program name defined in non-retentive program configuration.");
+	}
+| PROGRAM error optional_task_name ':' prev_declared_program_type_name optional_prog_conf_elements
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "no program name defined in program configuration.");
+	 yyerrok;
+	}
+| PROGRAM RETAIN error optional_task_name ':' prev_declared_program_type_name optional_prog_conf_elements
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "no program name defined in retentive program configuration.");
+	 yyerrok;
+	}
+| PROGRAM NON_RETAIN error optional_task_name ':' prev_declared_program_type_name optional_prog_conf_elements
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "no program name defined in non-retentive program configuration.");
+	 yyerrok;
+	}
+| PROGRAM program_name optional_task_name prev_declared_program_type_name optional_prog_conf_elements
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@3), locl(@4), "':' missing after program name or optional task name in program configuration.");
+	}
+| PROGRAM RETAIN program_name optional_task_name prev_declared_program_type_name optional_prog_conf_elements
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@4), locl(@5), "':' missing after program name or optional task name in program configuration.");
+	}
+| PROGRAM NON_RETAIN program_name optional_task_name prev_declared_program_type_name optional_prog_conf_elements
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@4), locl(@5), "':' missing after program name or optional task name in program configuration.");
+	}
+| PROGRAM program_name optional_task_name error prev_declared_program_type_name optional_prog_conf_elements
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@3), locl(@5), "expecting ':' after program name or optional task name in program configuration.");
+	 yyerrok;
+	}
+| PROGRAM RETAIN program_name optional_task_name error prev_declared_program_type_name optional_prog_conf_elements
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@4), locl(@6), "expecting ':' after program name or optional task name in program configuration.");
+	 yyerrok;
+	}
+| PROGRAM NON_RETAIN program_name optional_task_name error prev_declared_program_type_name optional_prog_conf_elements
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@4), locl(@6), "expecting ':' after program name or optional task name in program configuration.");
+	 yyerrok;
+	}
+| PROGRAM program_name optional_task_name ':' optional_prog_conf_elements
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@4), locl(@5), "no program type defined in program configuration.");
+	}
+| PROGRAM RETAIN program_name optional_task_name ':' optional_prog_conf_elements
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@5), locl(@6), "no program type defined in program configuration.");
+	}
+| PROGRAM NON_RETAIN program_name optional_task_name ':' optional_prog_conf_elements
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@5), locl(@6), "no program type defined in program configuration.");
+}
+/* ERROR_CHECK_END */
 ;
 // helper symbol for program_configuration //
 optional_task_name:
 // empty //
 	{$$ = NULL;}
 | WITH task_name
 	{$$ = $2;}
+/* ERROR_CHECK_BEGIN */
+| WITH error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "invalid tack name in optional task name of program configuration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 // helper symbol for program_configuration //
 optional_prog_conf_elements:
 // empty //
 	{$$ = NULL;}
 | '(' prog_conf_elements ')'
 	{$$ = $2;}
+/* ERROR_CHECK_BEGIN */
+| '(' error ')'
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "invalid program configuration elements in program configuration.");
+	 yyerrok;
+	}
+| '(' prog_conf_elements error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "')' missing at the end of program configuration elements in program configuration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 prog_conf_elements:
 prog_conf_element
 	{$$ = new prog_conf_elements_c(locloc(@$)); $$->add_element($1);}
 | prog_conf_elements ',' prog_conf_element
 	{$$ = $1; $$->add_element($3);}
+/* ERROR_CHECK_BEGIN */
+| prog_conf_elements prog_conf_element
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "',' missing in program configuration elements list.");
+	}
+| prog_conf_elements ',' error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid value for program configuration element in program configuration list.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 prog_conf_element:
 fb_task
 *       that have been declared in a scope outside the one we are
 *       currently parsing, so we must accept them to be any_identifier!
 */
 any_identifier WITH task_name
 	{$$ = new fb_task_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| any_identifier WITH error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid task name in function block configuration.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 /* NOTE:
 *  The semantics of configuring a program are rather confusing, so here is
 prog_cnxn:
 any_symbolic_variable ASSIGN prog_data_source
 	{$$ = new prog_cnxn_assign_c($1, $3, locloc(@$));}
 | any_symbolic_variable SENDTO data_sink
 	{$$ = new prog_cnxn_sendto_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| any_symbolic_variable constant
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "':=' missing between parameter and value in program configuration element.");
+	}
+| any_symbolic_variable enumerated_value
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "':=' missing between parameter and value in program configuration element.");
+	}
+| any_symbolic_variable data_sink
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "':=' or '=>' missing between parameter and variable in program configuration element.");
+	}
+| any_symbolic_variable error prog_data_source
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "expecting ':=' or '=>' after parameter in program configuration element.");
+	 yyerrok;
+	}
+| any_symbolic_variable ASSIGN error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid value or variable in program configuration assignment element.");
+	 yyerrok;
+	}
+| any_symbolic_variable SENDTO error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid variable in program configuration sendto element.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 prog_data_source:
 constant
 | enumerated_value
 ;
 instance_specific_initializations:
 VAR_CONFIG instance_specific_init_list END_VAR
 	{$$ = new instance_specific_initializations_c($2, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| VAR_CONFIG END_VAR
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no variable declared in configuration variable(s) initialization.");
+	}
+| VAR_CONFIG error instance_specific_init_list END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unexpected token after 'VAR_CONFIG' in configuration variable(s) initialization.");
+	 yyerrok;
+	}
+| VAR_CONFIG error END_VAR
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unknown error in configuration variable(s) initialization.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 // helper symbol for instance_specific_initializations //
 instance_specific_init_list:
 instance_specific_init ';'
 	{$$ = new instance_specific_init_list_c(locloc(@$)); $$->add_element($1);}
 | instance_specific_init_list instance_specific_init ';'
 	{$$ = $1; $$->add_element($2);}
+/* ERROR_CHECK_BEGIN */
+| instance_specific_init error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "';' missing at the end of configuration variable initialization.");
+	 yyerrok;
+	}
+| instance_specific_init_list instance_specific_init error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "';' missing at the end of configuration variable initialization.");
+	 yyerrok;
+	}
+| instance_specific_init_list ';'
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "unexpected ';' after configuration variable initialization.");
+	}
+/* ERROR_CHECK_END */
 ;
 instance_specific_init:
 //
 /* helper symbol for instance_specific_init */
 fb_initialization:
 function_block_type_name ASSIGN structure_initialization
 	{$$ = new fb_initialization_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| function_block_type_name structure_initialization
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "':=' missing between function block name and initialization in function block initialization.");
+	}
+| function_block_type_name error structure_initialization
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "expecting ':=' after function block name in function block initialization.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 /***********************************/
 /* B 2.1 Instructions and Operands */
 /***********************************/
 	{$$ = new instruction_list_c(locloc(@$)); $$->add_element($1);}
 | instruction_list il_instruction
 	{$$ = $1; $$->add_element($2);}
 | instruction_list pragma
 	{$$ = $1; $$->add_element($2);}
+/* ERROR_CHECK_BEGIN */
+| instruction_list error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "invalid IL instruction.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 il_instruction:
 | label ':' il_incomplete_instruction eol_list
 	{$$ = new il_instruction_c($1, $3, locloc(@$));}
 /* ERROR_CHECK_BEGIN */
 | error eol_list
 	{$$ = NULL;
-	 print_err_msg(current_filename, locf(@1), locl(@1), "error in IL instruction.");
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid IL instruction.");
 	 yyerrok;
 	}
-/* ERROR_CHECK_END */
+| il_incomplete_instruction error
-/* ERROR_CHECK_BEGIN */
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "EOL missing at the end of IL instruction.");
+	 yyerrok;
+	}
+| error ':' il_incomplete_instruction eol_list
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid label in IL instruction.");
+	 yyerrok;
+	}
+| label il_incomplete_instruction eol_list
+	{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "':' missing after label in IL instruction.");
+	}
+| label error il_incomplete_instruction eol_list
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "expecting ':' after label in IL instruction.");
+	 yyerrok;
+	}
 | label ':' error eol_list
 	{$$ = NULL;
-	 print_err_msg(current_filename, locf(@1), locl(@3), "error in IL instruction.");
+	 print_err_msg(current_filename, locf(@2), locl(@4), "invalid IL instruction.");
+	 yyerrok;
+	}
+| label ':' il_incomplete_instruction error
+	{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "EOL missing at the end of IL instruction.");
 	 yyerrok;
 	}
 /* ERROR_CHECK_END */
 ;
 	{$$ = new il_expression_c($1, $3, NULL, locloc(@$));}
 | il_expr_operator_clash '(' il_operand eol_list simple_instr_list ')'
 	{$$ = new il_expression_c($1, $3, $5, locloc(@$));}
 | il_expr_operator_clash_eol_list simple_instr_list ')'
 	{$$ = new il_expression_c($1, NULL, $2, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| il_expr_operator_noclash '(' eol_list error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@3), locl(@3), "')' missing at the end of IL expression.");
+	 yyerrok;
+	}
+| il_expr_operator_noclash '(' il_operand eol_list error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@4), locl(@4), "')' missing at the end of IL expression.");
+	 yyerrok;
+	}
+| il_expr_operator_noclash '(' eol_list simple_instr_list error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@4), locl(@4), "')' missing at the end of IL expression.");
+	 yyerrok;
+	}
+| il_expr_operator_noclash '(' il_operand eol_list simple_instr_list error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@5), locl(@5), "')' missing at the end of IL expression.");
+	 yyerrok;
+	}
+| il_expr_operator_clash '(' il_operand eol_list error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@4), locl(@4), "')' missing at the end of IL expression.");
+	 yyerrok;
+	}
+| il_expr_operator_clash '(' il_operand eol_list simple_instr_list error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@5), locl(@5), "')' missing at the end of IL expression.");
+	 yyerrok;
+	}
+| il_expr_operator_clash_eol_list simple_instr_list error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "')' missing at the end of IL expression.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 il_jump_operation:
 il_jump_operator label
 	{$$ = new il_jump_operation_c($1, $2, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| il_jump_operator error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "invalid label defined in IL jump operation.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 il_fb_call:
 // il_call_operator fb_name ['(' (EOL {EOL} [il_param_list]) | [il_operand_list] ')']
 	{$$ = new il_fb_call_c($1, $2, NULL, NULL, locloc(@$));}
 | il_call_operator prev_declared_fb_name '(' il_operand_list ')'
 	{$$ = new il_fb_call_c($1, $2, $4, NULL, locloc(@$));}
 | il_call_operator prev_declared_fb_name '(' eol_list il_param_list ')'
 	{$$ = new il_fb_call_c($1, $2, NULL, $5, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| il_call_operator error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "invalid function block name defined in IL function block call.");
+	 yyerrok;
+	}
+| il_call_operator '(' ')'
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no function block name defined in IL function block call.");
+	}
+| il_call_operator '(' eol_list ')'
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no function block name defined in IL function block call.");
+	}
+| il_call_operator '(' il_operand_list ')'
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no function block name defined in IL function block call.");
+	}
+| il_call_operator '(' eol_list il_param_list ')'
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no function block name defined in IL function block call.");
+	}
+| il_call_operator error '(' ')'
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "invalid function block name defined in IL function block call.");
+	 yyerrok;
+	}
+| il_call_operator error '(' eol_list ')'
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "invalid function block name defined in IL function block call.");
+	 yyerrok;
+	}
+| il_call_operator error '(' il_operand_list ')'
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "invalid function block name defined in IL function block call.");
+	 yyerrok;
+	}
+| il_call_operator error '(' eol_list il_param_list ')'
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "invalid function block name defined in IL function block call.");
+	 yyerrok;
+	}
+| il_call_operator prev_declared_fb_name ')'
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@3), "'(' missing after function block name defined in IL function block call.");
+	}
+| il_call_operator prev_declared_fb_name il_operand_list ')'
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@3), "'(' missing after function block name defined in IL function block call.");
+	}
+| il_call_operator prev_declared_fb_name '(' error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "')' missing at the end of IL function block call.");
+	 yyerrok;
+	}
+| il_call_operator prev_declared_fb_name '(' eol_list error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "')' missing at the end of IL function block call.");
+	 yyerrok;
+	}
+| il_call_operator prev_declared_fb_name '(' il_operand_list error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "')' missing at the end of IL function block call.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 /* NOTE: Please read note above the definition of function_name_without_clashes */
 il_formal_funct_call:
 * This is a lot of work, so I put it in a function
 * at the end of this file... il_operator_c_2_identifier_c()
 */
 | il_expr_operator_clash_eol_list il_param_list ')'
 	{$$ = new il_formal_funct_call_c(il_operator_c_2_identifier_c($1), $2, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| function_name_no_clashes '(' eol_list error ')'
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@3), locl(@5), "invalid parameter list defined in IL formal function call.");
+	 yyerrok;
+	}
+| function_name_simpleop_clashes '(' eol_list error ')'
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@3), locl(@5), "invalid parameter list defined in IL formal function call.");
+	 yyerrok;
+	}
+| il_expr_operator_clash_eol_list error ')'
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "invalid parameter list defined in IL formal function call.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 il_expr_operator_clash_eol_list:
 il_expr_operator_clash '(' eol_list
 	{$$ = $1;}
+/* ERROR_CHECK_BEGIN */
+| il_expr_operator_clash '(' error
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "EOL missing after '(' in IL instruction.");
+	}
+/* ERROR_CHECK_END */
 ;
 il_operand:
 variable
 il_operand_list2:
 il_operand ',' il_operand
 	{$$ = new il_operand_list_c(locloc(@$)); $$->add_element($1); $$->add_element($3);}
 | il_operand_list2 ',' il_operand
 	{$$ = $1; $$->add_element($3);}
+/* ERROR_CHECK_BEGIN */
+| il_operand_list2 il_operand
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "',' missing in IL operand list.");
+	}
+| il_formal_funct_call error il_operand
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "expecting ',' in IL operand list.");
+	 yyerrok;
+	}
+| il_formal_funct_call ',' error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "invalid operand in IL operand list.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 simple_instr_list:
 il_simple_instruction
 il_simple_instruction:
 il_simple_operation eol_list
 | il_expression eol_list
 | il_formal_funct_call eol_list
+/* ERROR_CHECK_BEGIN */
+| il_expression error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "EOL missing after expression IL instruction.");
+	 yyerrok;
+	}
+| il_formal_funct_call error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "EOL missing after formal function call IL instruction.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 /* NOTE: the correct definition of il_param_list is
 * il_param_list ::= {il_param_instruction} il_param_last_instruction
 il_param_list:
 il_param_instruction_list il_param_last_instruction
 	{$$ = $1; $$->add_element($2);}
 | il_param_last_instruction
 	{$$ = new il_param_list_c(locloc(@$)); $$->add_element($1);}
+/* ERROR_CHECK_BEGIN */
+| il_param_instruction_list error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid parameter assignment in parameter assignment list.");
+	 yyerrok;
+	}
+| il_param_last_instruction il_param_last_instruction
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "',' missing at the end of parameter assignment in parameter assignment list.");
+	}
+| il_param_instruction_list il_param_last_instruction il_param_last_instruction
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "',' missing at the end of parameter assignment in parameter assignment list.");
+	}
+/* ERROR_CHECK_END */
 ;
 /* Helper symbol for il_param_list */
 il_param_instruction_list:
 il_param_instruction
 	{$$ = new il_param_list_c(locloc(@$)); $$->add_element($1);}
 | il_param_instruction_list il_param_instruction
 	{$$ = $1; $$->add_element($2);}
+/* ERROR_CHECK_BEGIN */
+| il_param_last_instruction il_param_instruction
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "',' missing at the end of parameter assignment in parameter assignment list.");
+	}
+| il_param_instruction_list il_param_last_instruction il_param_instruction
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "',' missing at the end of parameter assignment in parameter assignment list.");
+	}
+/* ERROR_CHECK_END */
 ;
 il_param_instruction:
 il_param_assignment ',' eol_list
 | il_param_out_assignment ',' eol_list
+/* ERROR_CHECK_BEGIN */
+| il_param_assignment ',' error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "EOL missing at the end of parameter assignment in parameter assignment list.");
+	 yyerrok;
+	}
+| il_param_out_assignment ',' error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "EOL missing at the end of parameter out assignment in parameter assignment list.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 il_param_last_instruction:
 il_param_assignment eol_list
 | il_param_out_assignment eol_list
+/* ERROR_CHECK_BEGIN */
+| il_param_assignment error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "EOL missing at the end of last parameter assignment in parameter assignment list.");
+	 yyerrok;
+	}
+| il_param_out_assignment error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "EOL missing at the end of last parameter out assignment in parameter assignment list.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 il_param_assignment:
 il_assign_operator il_operand
 	{$$ = new il_param_assignment_c($1, $2, NULL, locloc(@$));}
 | il_assign_operator '(' eol_list simple_instr_list ')'
 	{$$ = new il_param_assignment_c($1, NULL, $4, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| error il_operand
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid operator in parameter assignment.");
+	 yyerrok;
+	}
+| error '(' eol_list simple_instr_list ')'
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid operator in parameter assignment.");
+	 yyerrok;
+	}
+| il_assign_operator error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "invalid operand defined in parameter assignment.");
+	 yyerrok;
+	}
+| il_assign_operator '(' ')'
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "no instruction list defined in parameter assignment.");
+	 yyerrok;
+	}
+| il_assign_operator '(' error ')'
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "invalid instruction list defined in parameter assignment.");
+	 yyerrok;
+	}
+| il_assign_operator '(' eol_list simple_instr_list error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "')' missing at the end of instruction list defined in parameter assignment.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 il_param_out_assignment:
 il_assign_out_operator variable
 	{$$ = new il_param_out_assignment_c($1, $2, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| il_assign_out_operator error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "invalid variable defined in parameter out assignment.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 /*******************/
 il_assign_operator:
 /*  variable_name ASSIGN */
 any_identifier ASSIGN
+/* ERROR_CHECK_BEGIN */
+| error ASSIGN
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid parameter defined in parameter assignment.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 il_assign_out_operator:
 /*  variable_name SENDTO */
 sendto_identifier SENDTO
 	{$$ = new il_assign_out_operator_c(NULL, $1, locloc(@$));}
 /*| NOT variable_name SENDTO */
 | NOT sendto_identifier SENDTO
 	{$$ = new il_assign_out_operator_c(new not_paramassign_c(locloc(@1)), $2, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| error SENDTO
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid parameter defined in parameter out assignment.");
+	 yyerrok;
+	}
+| NOT SENDTO
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no paramter defined in parameter out assignment.");
+	}
+| NOT error SENDTO
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "invalid parameter defined in parameter out assignment.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 il_call_operator:
 CAL_operator
 /***********************/
 expression:
 xor_expression
 | expression OR xor_expression
 	{$$ = new or_expression_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| expression OR error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid expression after 'OR' in ST expression.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 xor_expression:
 and_expression
 | xor_expression XOR and_expression
 	{$$ = new xor_expression_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| xor_expression XOR error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid expression after 'XOR' in ST expression.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 and_expression:
 comparison
 | and_expression '&' comparison
 *       but we leave it in nevertheless just in case we later decide
 *       to remove theh AND2 token...
 */
 | and_expression AND2 comparison
 	{$$ = new and_expression_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| and_expression '&' error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid expression after '&' in ST expression.");
+	 yyerrok;
+	}
+| and_expression AND error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid expression after 'AND' in ST expression.");
+	 yyerrok;
+	}
+| and_expression AND2 error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid expression after '&' in ST expression.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 comparison:
 equ_expression
 | comparison '=' equ_expression
 	{$$ = new equ_expression_c($1, $3, locloc(@$));}
 | comparison OPER_NE equ_expression
 	{$$ = new notequ_expression_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| comparison '=' error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid expression after '=' in ST expression.");
+	 yyerrok;
+	}
+| comparison OPER_NE error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid expression after '<>' in ST expression.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 equ_expression:
 add_expression
 | equ_expression '<' add_expression
 	{$$ = new gt_expression_c($1, $3, locloc(@$));}
 | equ_expression OPER_LE add_expression
 	{$$ = new le_expression_c($1, $3, locloc(@$));}
 | equ_expression OPER_GE add_expression
 	{$$ = new ge_expression_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| equ_expression '<' error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid expression after '<' in ST expression.");
+	 yyerrok;
+	}
+| equ_expression '>' error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid expression after '>' in ST expression.");
+	 yyerrok;
+	}
+| equ_expression OPER_LE error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid expression after '<=' in ST expression.");
+	 yyerrok;
+	}
+| equ_expression OPER_GE error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid expression after '>=' in ST expression.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 /* Not required...
 comparison_operator: '<' | '>' | '>=' '<='
 */
 term
 | add_expression '+' term
 	{$$ = new add_expression_c($1, $3, locloc(@$));}
 | add_expression '-' term
 	{$$ = new sub_expression_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| add_expression '+' error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid expression after '+' in ST expression.");
+	 yyerrok;
+	}
+| add_expression '-' error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid expression after '-' in ST expression.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 /* Not required...
 add_operator: '+' | '-'
 */
 	{$$ = new mul_expression_c($1, $3, locloc(@$));}
 | term '/' power_expression
 	{$$ = new div_expression_c($1, $3, locloc(@$));}
 | term MOD power_expression
 	{$$ = new mod_expression_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| term '*' error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid expression after '*' in ST expression.");
+	 yyerrok;
+	}
+| term '/' error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid expression after '/' in ST expression.");
+	 yyerrok;
+	}
+| term MOD error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid expression after 'MOD' in ST expression.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 /* Not required...
 multiply_operator: '*' | '/' | 'MOD'
 */
 power_expression:
 unary_expression
 | power_expression OPER_EXP unary_expression
 	{$$ = new power_expression_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| power_expression OPER_EXP error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid expression after '**' in ST expression.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 unary_expression:
 primary_expression
 | '-' primary_expression
 	{$$ = new neg_expression_c($2, locloc(@$));}
 | NOT primary_expression
 	{$$ = new not_expression_c($2, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| '-' error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "invalid expression after '-' in ST expression.");
+	 yyerrok;
+	}
+| NOT error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "invalid expression after 'NOT' in ST expression.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 /* Not required...
 unary_operator: '-' | 'NOT'
 */
 | enumerated_value
 | variable
 | '(' expression ')'
 	{$$ = $2;}
 |  function_invocation
+/* ERROR_CHECK_BEGIN */
+| '(' expression error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "')' missing at the end of expression in ST expression.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 /* intermediate helper symbol for primary_expression */
 /* NOTE: function_name includes the standard function name 'NOT' !
 /*  function_name '(' [param_assignment_list] ')' */
 function_name_no_NOT_clashes '(' param_assignment_formal_list ')'
 	{$$ = new function_invocation_c($1, $3, locloc(@$));}
 | function_name_no_NOT_clashes '(' param_assignment_nonformal_list ')'
 	{$$ = new function_invocation_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| function_name_no_NOT_clashes param_assignment_formal_list ')'
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "'(' missing after function name in ST expression.");
+	}
+| function_name_no_NOT_clashes error param_assignment_formal_list ')'
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "expecting '(' after function name in ST expression.");
+	 yyerrok;
+	}
+| function_name_no_NOT_clashes error param_assignment_nonformal_list ')'
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "expecting '(' after function name in ST expression.");
+	 yyerrok;
+	}
+| function_name_no_NOT_clashes '(' ')'
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "no parameter defined in function invocation of ST expression.");
+	}
+| function_name_no_NOT_clashes '(' error ')'
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "invalid parameter(s) defined in function invocation of ST expression.");
+	 yyerrok;
+	}
+| function_name_no_NOT_clashes '(' param_assignment_formal_list error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "')' missing at the end of function invocation in ST expression.");
+	 yyerrok;
+	}
+| function_name_no_NOT_clashes '(' param_assignment_nonformal_list error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "')' missing at the end of function invocation in ST expression.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 /********************/
 /* B 3.2 Statements */
 | statement_list statement ';'
 	{$$ = $1; $$->add_element($2);}
 | statement_list pragma
 	{$$ = $1; $$->add_element($2);}
 /* ERROR_CHECK_BEGIN */
+| statement_list error
+	{$$ = $1;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "';' missing at the end of statement in ST statement.");
+	 yyerrok;
+	}
 | statement_list error ';'
 	{$$ = $1;
-	 print_err_msg(current_filename, locf(@2), locl(@2), "error in statement.");
+	 print_err_msg(current_filename, locf(@1), locl(@3), "invalid statement in ST statement.");
-	 /* yychar */
+	 yyerrok;
+	}
+| statement_list statement error
+	{$$ = $1;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "';' missing at the end of statement in ST statement.");
 	 yyerrok;
 	}
 /* ERROR_CHECK_END */
 ;
 /* B 3.2.1 Assignment Statements */
 /*********************************/
 assignment_statement:
 variable ASSIGN expression
 	{$$ = new assignment_statement_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| variable ASSIGN error
+	{$$ = $1;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "invalid expression after ':=' in ST assignment statement.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 	{$$ = new fb_invocation_c($1, NULL, locloc(@$));	}
 | prev_declared_fb_name '(' param_assignment_formal_list ')'
 	{$$ = new fb_invocation_c($1, $3, locloc(@$));}
 | prev_declared_fb_name '(' param_assignment_nonformal_list ')'
 	{$$ = new fb_invocation_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| prev_declared_fb_name ')'
+	{$$ = $1;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "'(' missing after function block name in ST statement.");
+	}
+| prev_declared_fb_name param_assignment_formal_list ')'
+	{$$ = $1;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "'(' missing after function block name in ST statement.");
+	}
+| prev_declared_fb_name error ')'
+	{$$ = $1;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "expecting '(' after function block name in ST statement.");
+	 yyerrok;
+	}
+| prev_declared_fb_name error param_assignment_formal_list ')'
+	{$$ = $1;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "expecting '(' after function block name in ST statement.");
+	 yyerrok;
+	}
+| prev_declared_fb_name error param_assignment_nonformal_list ')'
+	{$$ = $1;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "expecting '(' after function block name in ST statement.");
+	 yyerrok;
+	}
+| prev_declared_fb_name '(' error ')'
+	{$$ = $1;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "invalid parameter list in function block invocation in ST statement.");
+	 yyerrok;
+	}
+| prev_declared_fb_name '(' error
+	{$$ = $1;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "')' missing after parameter list of function block invocation in ST statement.");
+	 yyerrok;
+	}
+| prev_declared_fb_name '(' param_assignment_formal_list error
+	{$$ = $1;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "')' missing after parameter list of function block invocation in ST statement.");
+	 yyerrok;
+	}
+| prev_declared_fb_name '(' param_assignment_nonformal_list error
+	{$$ = $1;
+	 print_err_msg(current_filename, locf(@1), locl(@1), "')' missing after parameter list of function block invocation in ST statement.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 /* helper symbol for
 * - fb_invocation
 param_assignment_formal_list:
 param_assignment_formal
 	{$$ = new param_assignment_list_c(locloc(@$)); $$->add_element($1);}
 | param_assignment_formal_list ',' param_assignment_formal
 	{$$ = $1; $$->add_element($3);}
+/* ERROR_CHECK_BEGIN */
+| param_assignment_formal_list error param_assignment_formal
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "expecting ',' in ST parameter assignment list.");
+	 yyerrok;
+	}
+| param_assignment_formal_list ',' error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid parameter assignment in ST parameter assignment list.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 /* helper symbol for
 * - fb_invocation
 * - function_invocation
 param_assignment_nonformal_list:
 param_assignment_nonformal
 	{$$ = new param_assignment_list_c(locloc(@$)); $$->add_element($1);}
 | param_assignment_nonformal_list ',' param_assignment_nonformal
 	{$$ = $1; $$->add_element($3);}
+/* ERROR_CHECK_BEGIN */
+| param_assignment_nonformal_list ',' error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "invalid parameter assignment in ST parameter assignment list.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 /* NOTE: According to the IEC 61131-3 standard, there are two possible
 *       syntaxes for calling function blocks within ST.
 	{$$ = new output_variable_param_assignment_c(NULL,$1, $3, locloc(@$));}
 /*| NOT variable_name SENDTO variable */
 /*| NOT any_identifier SENDTO variable*/
 | NOT sendto_identifier SENDTO variable
 	{$$ = new output_variable_param_assignment_c(new not_paramassign_c(locloc(@$)),$2, $4, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| any_identifier ASSIGN error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "invalid expression in ST formal parameter assignment.");
+	 yyerrok;
+	}
+| sendto_identifier SENDTO error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "invalid expression in ST formal parameter out assignment.");
+	 yyerrok;
+	}
+| NOT SENDTO variable
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no parameter name defined in ST formal parameter out negated assignment.");
+	}
+| NOT error SENDTO variable
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "invalid parameter name defined in ST formal parameter out negated assignment.");
+	 yyerrok;
+	}
+| NOT sendto_identifier SENDTO error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "invalid expression in ST formal parameter out negated assignment.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 if_statement:
 IF expression THEN statement_list elseif_statement_list END_IF
 	{$$ = new if_statement_c($2, $4, $5, NULL, locloc(@$));}
 | IF expression THEN statement_list elseif_statement_list ELSE statement_list END_IF
 	{$$ = new if_statement_c($2, $4, $5, $7, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| IF THEN statement_list elseif_statement_list END_IF
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no test expression defined in ST 'IF' statement.");
+	}
+| IF THEN statement_list elseif_statement_list ELSE statement_list END_IF
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no test expression defined in ST 'IF' statement.");
+	}
+| IF error THEN statement_list elseif_statement_list END_IF
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "invalid test expression defined for ST 'IF' statement.");
+	 yyerrok;
+	}
+| IF error THEN statement_list elseif_statement_list ELSE statement_list END_IF
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "invalid test expression defined for ST 'IF' statement.");
+	 yyerrok;
+	}
+| IF expression error statement_list elseif_statement_list END_IF
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "expecting 'THEN' after test expression in ST 'IF' statement.");
+	 yyerrok;
+	}
+| IF expression error statement_list elseif_statement_list ELSE statement_list END_IF
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "expecting 'THEN' after test expression in ST 'IF' statement.");
+	 yyerrok;
+	}
+| IF expression THEN elseif_statement_list END_IF
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@3), locl(@4), "no statement defined after 'THEN' in ST 'IF' statement.");
+	}
+| IF expression THEN elseif_statement_list ELSE statement_list END_IF
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@3), locl(@4), "no statement defined after 'THEN' in ST 'IF' statement.");
+	}
+| IF expression THEN statement_list elseif_statement_list ELSE END_IF
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@6), locl(@7), "no statement defined after 'ELSE' in ST 'IF' statement.");
+	}
+| IF expression THEN statement_list elseif_statement_list ELSE error END_IF
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@6), locl(@8), "invalid statement defined after 'ELSE' in ST 'IF' statement.");
+	 yyerrok;
+	}
+| IF error END_IF
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unknown error in ST 'IF' statement.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 /* helper symbol for if_statement */
 elseif_statement_list:
 /* empty */
 /* helper symbol for elseif_statement_list */
 elseif_statement:
 ELSIF expression THEN statement_list
 	{$$ = new elseif_statement_c($2, $4, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| ELSIF THEN statement_list
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no test expression defined for 'ELSEIF' statement in ST 'IF' statement.");
+	}
+| ELSIF error THEN statement_list
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "invalid test expression defined for 'ELSEIF' statement in ST 'IF' statement.");
+	 yyerrok;
+	}
+| ELSIF expression error statement_list
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "expecting 'THEN' after test expression in 'ELSEIF' statement of ST 'IF' statement.");
+	 yyerrok;
+	}
+| ELSIF expression THEN error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@3), locl(@3), "invalid statement list in 'ELSEIF' statement of ST 'IF' statement.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 case_statement:
 CASE expression OF case_element_list END_CASE
 	{$$ = new case_statement_c($2, $4, NULL, locloc(@$));}
 | CASE expression OF case_element_list ELSE statement_list END_CASE
 	{$$ = new case_statement_c($2, $4, $6, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| CASE OF case_element_list END_CASE
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no test expression defined in ST 'CASE' statement.");
+	}
+| CASE OF case_element_list ELSE statement_list END_CASE
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no test expression defined in ST 'CASE' statement.");
+	}
+| CASE error OF case_element_list END_CASE
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "invalid test expression defined for ST 'CASE' statement.");
+	 yyerrok;
+	}
+| CASE error OF case_element_list ELSE statement_list END_CASE
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "invalid test expression defined for ST 'CASE' statement.");
+	 yyerrok;
+	}
+| CASE expression error case_element_list END_CASE
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "expecting 'OF' after test expression in ST 'CASE' statement.");
+	 yyerrok;
+	}
+| CASE expression error case_element_list ELSE statement_list END_CASE
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "expecting 'OF' after test expression in ST 'CASE' statement.");
+	 yyerrok;
+	}
+| CASE expression OF END_CASE
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@3), locl(@4), "no case element(s) defined after 'OF' in ST 'CASE' statement.");
+	}
+| CASE expression OF ELSE statement_list END_CASE
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@3), locl(@4), "no case element(s) defined after 'OF' in ST 'CASE' statement.");
+	}
+| CASE expression OF error END_CASE
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@3), locl(@5), "invalid case element(s) defined after 'OF' in ST 'CASE' statement.");
+	 yyerrok;
+	}
+| CASE expression OF error ELSE statement_list END_CASE
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@3), locl(@5), "invalid case element(s) defined after 'OF' in ST 'CASE' statement.");
+	 yyerrok;
+	}
+| CASE expression OF case_element_list ELSE END_CASE
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@5), locl(@6), "no statement defined after 'ELSE' in ST 'CASE' statement.");
+	}
+| CASE expression OF case_element_list ELSE error END_CASE
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@5), locl(@7), "invalid statement defined after 'ELSE' in ST 'CASE' statement.");
+	 yyerrok;
+	}
+| CASE error END_CASE
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unknown error in ST 'CASE' statement.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 /* helper symbol for case_statement */
 case_element_list:
 case_element:
 case_list ':' statement_list
 	{$$ = new case_element_c($1, $3, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| case_list statement_list
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "':' missing after case list in ST 'CASE' statement.");
+	}
+| case_list ':' error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "invalid statement in case element of ST 'CASE' statement.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 case_list:
 case_list_element
 	{$$ = new case_list_c(locloc(@$)); $$->add_element($1);}
 | case_list ',' case_list_element
 	{$$ = $1; $$->add_element($3);}
+/* ERROR_CHECK_BEGIN */
+| case_list ',' error
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@2), "invalid case in case list of ST parameter assignment list.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 case_list_element:
 signed_integer
 for_statement:
 FOR control_variable ASSIGN expression TO expression BY expression DO statement_list END_FOR
 	{$$ = new for_statement_c($2, $4, $6, $8, $10, locloc(@$));}
 | FOR control_variable ASSIGN expression TO expression DO statement_list END_FOR
 	{$$ = new for_statement_c($2, $4, $6, NULL, $8, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| FOR ASSIGN expression TO expression BY expression DO statement_list END_FOR
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no control variable defined in ST 'FOR' statement.");
+	}
+| FOR ASSIGN expression TO expression DO statement_list END_FOR
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no control variable defined in ST 'FOR' statement.");
+	}
+| FOR error ASSIGN expression TO expression BY expression DO statement_list END_FOR
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "invalid control variable defined for ST 'FOR' statement.");
+	 yyerrok;
+	}
+| FOR error ASSIGN expression TO expression DO statement_list END_FOR
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "invalid control variable defined for ST 'FOR' statement.");
+	 yyerrok;
+	}
+| FOR control_variable expression TO expression BY expression DO statement_list END_FOR
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@3), "':=' missing between control variable and start expression in ST 'FOR' statement.");
+	}
+| FOR control_variable expression TO expression DO statement_list END_FOR
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@2), locl(@3), "':=' missing between control variable and start expression in ST 'FOR' statement.");
+	}
+| FOR control_variable error expression TO expression BY expression DO statement_list END_FOR
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "expecting ':=' between control variable and start expression in ST 'FOR' statement.");
+	 yyerrok;
+	}
+| FOR control_variable error expression TO expression DO statement_list END_FOR
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "expecting ':=' between control variable and start expression in ST 'FOR' statement.");
+	 yyerrok;
+	}
+| FOR control_variable ASSIGN TO expression BY expression DO statement_list END_FOR
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@3), locl(@4), "no start expression defined in ST 'FOR' statement.");
+	}
+| FOR control_variable ASSIGN TO expression DO statement_list END_FOR
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@3), locl(@4), "no start expression defined in ST 'FOR' statement.");
+	}
+| FOR control_variable ASSIGN error TO expression BY expression DO statement_list END_FOR
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@3), locl(@5), "invalid start expression defined in ST 'FOR' statement.");
+	 yyerrok;
+	}
+| FOR control_variable ASSIGN error TO expression DO statement_list END_FOR
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@3), locl(@5), "invalid start expression in ST 'FOR' statement.");
+	 yyerrok;
+	}
+| FOR control_variable ASSIGN expression error expression BY expression DO statement_list END_FOR
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@4), locl(@6), "expecting 'TO' between start expression and end expression in ST 'FOR' statement.");
+	 yyerrok;
+	}
+| FOR control_variable ASSIGN expression error expression DO statement_list END_FOR
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@4), locl(@6), "expecting 'TO' between start expression and end expression in ST 'FOR' statement.");
+	 yyerrok;
+	}
+| FOR control_variable ASSIGN expression TO expression error expression DO statement_list END_FOR
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@6), locl(@8), "expecting 'BY' between end expression and step expression in ST 'FOR' statement.");
+	 yyerrok;
+	}
+| FOR control_variable ASSIGN expression TO expression BY expression error statement_list END_FOR
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@8), locl(@10), "expecting 'DO' after step expression in ST 'FOR' statement.");
+	 yyerrok;
+	}
+| FOR control_variable ASSIGN expression TO expression error statement_list END_FOR
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@6), locl(@8), "expecting 'DO' after end expression in ST 'FOR' statement.");
+	 yyerrok;
+	}
+| FOR control_variable ASSIGN expression TO expression BY expression DO END_FOR
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@9), locl(@10), "no statement(s) defined after 'DO' in ST 'FOR' statement.");
+	 yyerrok;
+	}
+| FOR control_variable ASSIGN expression TO expression DO END_FOR
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@7), locl(@8), "no statement(s) defined after 'DO' in ST 'FOR' statement.");
+	 yyerrok;
+	}
+| FOR control_variable ASSIGN expression TO expression BY expression DO error END_FOR
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@9), locl(@11), "invalid statement(s) defined after 'DO' in ST 'FOR' statement.");
+	 yyerrok;
+	}
+| FOR control_variable ASSIGN expression TO expression DO error END_FOR
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@7), locl(@9), "invalid statement(s) defined after 'DO' in ST 'FOR' statement.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 /* The spec has the syntax
 * control_variable: identifier;
 * but then defines the semantics of control_variable
 while_statement:
 WHILE expression DO statement_list END_WHILE
 	{$$ = new while_statement_c($2, $4, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| WHILE DO statement_list END_WHILE
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no test expression defined in ST 'WHILE' statement.");
+	}
+| WHILE error DO statement_list END_WHILE
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "invalid test expression defined for ST 'WHILE' statement.");
+	 yyerrok;
+	}
+| WHILE expression error statement_list END_WHILE
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@2), locl(@4), "expecting 'DO' after test expression in ST 'WHILE' statement.");
+	 yyerrok;
+	}
+| WHILE expression DO END_WHILE
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@3), locl(@4), "no statement(s) defined after 'DO' in ST 'WHILE' statement.");
+	}
+| WHILE expression DO error END_WHILE
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@3), locl(@5), "invalid statement(s) defined after 'DO' in ST 'WHILE' statement.");
+	 yyerrok;
+	}
+| WHILE error END_WHILE
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unknown error in ST 'WHILE' statement.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 repeat_statement:
 REPEAT statement_list UNTIL expression END_REPEAT
 	{$$ = new repeat_statement_c($2, $4, locloc(@$));}
+/* ERROR_CHECK_BEGIN */
+| REPEAT UNTIL expression END_REPEAT
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@1), locl(@2), "no statement(s) defined after 'REPEAT' in ST 'REPEAT' statement.");
+	}
+| REPEAT error UNTIL expression END_REPEAT
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "invalid statement(s) defined after 'REPEAT' for ST 'REPEAT' statement.");
+	 yyerrok;
+	}
+| REPEAT statement_list UNTIL END_REPEAT
+{$$ = NULL;
+	 yynerrs++;
+	 print_err_msg(current_filename, locf(@3), locl(@4), "no test expression defined after 'UNTIL' in ST 'REPEAT' statement.");
+	}
+| REPEAT statement_list UNTIL error END_REPEAT
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@3), locl(@5), "invalid test expression defined after 'UNTIL' in ST 'REPEAT' statement.");
+	 yyerrok;
+	}
+| REPEAT error END_REPEAT
+{$$ = NULL;
+	 print_err_msg(current_filename, locf(@1), locl(@3), "unknown error in ST 'REPEAT' statement.");
+	 yyerrok;
+	}
+/* ERROR_CHECK_END */
 ;
 exit_statement:
 EXIT	{$$ = new exit_statement_c(locloc(@$));}
 int first_line,
 int first_column,
 int last_line,
 int last_column,
 const char *additional_error_msg) {
-fprintf(stderr, "error %d: %s\n", yynerrs /* a global variable */, additional_error_msg);
+fprintf(stderr, "%s:%d: error : %s\n", filename, first_line, additional_error_msg);
+//fprintf(stderr, "error %d: %s\n", yynerrs /* a global variable */, additional_error_msg);
 print_include_stack();
-fprintf(stderr, "%s(%d-%d): %s\n", filename, first_line, last_line, current_error_msg);
+//fprintf(stderr, "%s(%d-%d): %s\n", filename, first_line, last_line, current_error_msg);
 }
 /* convert between an il_operator to a function name */

changeset 131	f55ef301e14c
parent 121	9e8ce092e169
child 133	fff75b8283be