stage3/print_datatypes_error.cc
changeset 625 c0bda77b37a0
parent 558 9273dfc5fa7c
child 676 ca4f17211251
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/stage3/print_datatypes_error.cc	Wed Aug 22 16:46:17 2012 +0200
@@ -0,0 +1,1290 @@
+/*
+ *  matiec - a compiler for the programming languages defined in IEC 61131-3
+ *
+ *  Copyright (C) 2009-2011  Mario de Sousa (msousa@fe.up.pt)
+ *  Copyright (C) 2011-2012 Manuele Conti (manuele.conti@sirius-es.it)
+ *  Copyright (C) 2011-2012 Matteo Facchinetti (matteo.facchinetti@sirius-es.it)
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ *
+ * This code is made available on the understanding that it will not be
+ * used in safety-critical situations without a full and competent review.
+ */
+
+/*
+ * An IEC 61131-3 compiler.
+ *
+ * Based on the
+ * FINAL DRAFT - IEC 61131-3, 2nd Ed. (2001-12-10)
+ *
+ */
+
+/* NOTE: The algorithm implemented here assumes that the symbol_c.candidate_datatype, and the symbol_c.datatype 
+ *       annotations have already been apropriately filled in!
+ *       BEFORE running this visitor, be sure to CALL the fill_candidate_datatypes_c, and the narrow_candidate_datatypes_c visitors!
+ */
+
+
+/*
+ *  By analysing the candidate datatype lists, as well as the chosen datatype for each expression, determine
+ *  if an datatype error has been found, and if so, print out an error message.
+ */
+
+
+#include "print_datatypes_error.hh"
+#include "datatype_functions.hh"
+
+#include <typeinfo>
+#include <list>
+#include <string>
+#include <string.h>
+#include <strings.h>
+
+
+
+
+
+
+#define FIRST_(symbol1, symbol2) (((symbol1)->first_order < (symbol2)->first_order)   ? (symbol1) : (symbol2))
+#define  LAST_(symbol1, symbol2) (((symbol1)->last_order  > (symbol2)->last_order)    ? (symbol1) : (symbol2))
+
+#define STAGE3_ERROR(error_level, symbol1, symbol2, ...) {                                                                  \
+  if (current_display_error_level >= error_level) {                                                                         \
+    fprintf(stderr, "%s:%d-%d..%d-%d: error: ",                                                                             \
+            FIRST_(symbol1,symbol2)->first_file, FIRST_(symbol1,symbol2)->first_line, FIRST_(symbol1,symbol2)->first_column,\
+                                                 LAST_(symbol1,symbol2) ->last_line,  LAST_(symbol1,symbol2) ->last_column);\
+    fprintf(stderr, __VA_ARGS__);                                                                                           \
+    fprintf(stderr, "\n");                                                                                                  \
+    il_error = true;                                                                                                        \
+    error_count++;                                                                                                     \
+  }                                                                                                                         \
+}  
+
+
+#define STAGE3_WARNING(symbol1, symbol2, ...) {                                                                             \
+    fprintf(stderr, "%s:%d-%d..%d-%d: warning: ",                                                                           \
+            FIRST_(symbol1,symbol2)->first_file, FIRST_(symbol1,symbol2)->first_line, FIRST_(symbol1,symbol2)->first_column,\
+                                                 LAST_(symbol1,symbol2) ->last_line,  LAST_(symbol1,symbol2) ->last_column);\
+    fprintf(stderr, __VA_ARGS__);                                                                                           \
+    fprintf(stderr, "\n");                                                                                                  \
+    warning_found = true;                                                                                                   \
+}  
+
+
+/* set to 1 to see debug info during execution */
+static int debug = 0;
+
+print_datatypes_error_c::print_datatypes_error_c(symbol_c *ignore) {
+	error_count = 0;
+	warning_found = false;
+	current_display_error_level = error_level_default;
+}
+
+print_datatypes_error_c::~print_datatypes_error_c(void) {
+}
+
+int print_datatypes_error_c::get_error_count() {
+	return error_count;
+}
+
+
+
+
+
+/* Verify if the datatypes of all prev_il_instructions are valid and equal!  */
+static bool are_all_datatypes_of_prev_il_instructions_datatypes_equal(il_instruction_c *symbol) {
+	if (NULL == symbol) ERROR;
+	bool res;
+	
+	if (symbol->prev_il_instruction.size() > 0)
+		res = is_type_valid(symbol->prev_il_instruction[0]->datatype);
+
+	for (unsigned int i = 1; i < symbol->prev_il_instruction.size(); i++)
+		res &= is_type_equal(symbol->prev_il_instruction[i-1]->datatype, symbol->prev_il_instruction[i]->datatype);
+	
+	return res;
+}
+
+
+
+
+/* a helper function... */
+symbol_c *print_datatypes_error_c::base_type(symbol_c *symbol) {
+	/* NOTE: symbol == NULL is valid. It will occur when, for e.g., an undefined/undeclared symbolic_variable is used
+	 *       in the code.
+	 */
+	if (symbol == NULL) return NULL;
+	return (symbol_c *)symbol->accept(search_base_type);
+}
+
+
+
+/*
+typedef struct {
+  symbol_c *function_name,
+  symbol_c *nonformal_operand_list,
+  symbol_c *   formal_operand_list,
+
+  std::vector <symbol_c *> &candidate_functions,  
+  symbol_c &*called_function_declaration,
+  int      &extensible_param_count
+} generic_function_call_t;
+*/
+void print_datatypes_error_c::handle_function_invocation(symbol_c *fcall, generic_function_call_t fcall_data) {
+	symbol_c *param_value, *param_name;
+	function_call_param_iterator_c fcp_iterator(fcall);
+	bool function_invocation_error = false;
+	const char *POU_str = NULL;
+
+	if (generic_function_call_t::POU_FB       == fcall_data.POU_type)  POU_str = "FB";
+	if (generic_function_call_t::POU_function == fcall_data.POU_type)  POU_str = "function";
+	if (NULL == POU_str) ERROR;
+
+	if ((NULL != fcall_data.formal_operand_list) && (NULL != fcall_data.nonformal_operand_list)) 
+		ERROR;
+
+	symbol_c *f_decl = fcall_data.called_function_declaration;
+	if ((NULL == f_decl) && (generic_function_call_t::POU_FB ==fcall_data.POU_type)) {
+		/* Due to the way the syntax analysis is buit (i.e. stage 2), this should never occur. */
+		/* I.e., a FB invocation using an undefined FB variable is not possible in the current implementation of stage 2. */
+		ERROR;
+	}
+	if (NULL == f_decl) {
+		/* we now try to find any function declaration with the same name, just so we can provide some relevant error messages */
+		function_symtable_t::iterator lower = function_symtable.lower_bound(fcall_data.function_name);
+		if (lower == function_symtable.end()) ERROR;
+		f_decl = function_symtable.get_value(lower);
+	}
+
+	if (NULL != fcall_data.formal_operand_list) {
+		fcall_data.formal_operand_list->accept(*this);
+		if (NULL != f_decl) {
+			function_param_iterator_c fp_iterator(f_decl);
+			while ((param_name = fcp_iterator.next_f()) != NULL) {
+				param_value = fcp_iterator.get_current_value();
+
+				/* Check if there are duplicate parameter values */
+				if(fcp_iterator.search_f(param_name) != param_value) {
+					function_invocation_error = true;
+					STAGE3_ERROR(0, param_name, param_name, "Duplicate parameter '%s' when invoking %s '%s'", ((identifier_c *)param_name)->value, POU_str, ((identifier_c *)fcall_data.function_name)->value);
+					continue; /* jump to next parameter */
+				}
+
+				/* Find the corresponding parameter in function declaration */
+				if (NULL == fp_iterator.search(param_name)) {
+					function_invocation_error = true;
+					STAGE3_ERROR(0, param_name, param_name, "Invalid parameter '%s' when invoking %s '%s'", ((identifier_c *)param_name)->value, POU_str, ((identifier_c *)fcall_data.function_name)->value);
+					continue; /* jump to next parameter */
+				} 
+
+				/* check whether direction (IN, OUT, IN_OUT) and assignment types (:= , =>) are compatible !!! */
+				/* Obtaining the assignment direction:  := (assign_in) or => (assign_out) */
+				function_call_param_iterator_c::assign_direction_t call_param_dir = fcp_iterator.get_assign_direction();
+				/* Get the parameter direction: IN, OUT, IN_OUT */
+				function_param_iterator_c::param_direction_t param_dir = fp_iterator.param_direction();
+				if          (function_call_param_iterator_c::assign_in  == call_param_dir) {
+					if ((function_param_iterator_c::direction_in    != param_dir) &&
+					    (function_param_iterator_c::direction_inout != param_dir)) {
+						function_invocation_error = true;
+						STAGE3_ERROR(0, param_name, param_name, "Invalid assignment syntax ':=' used for parameter '%s', when invoking %s '%s'", ((identifier_c *)param_name)->value, POU_str, ((identifier_c *)fcall_data.function_name)->value);
+						continue; /* jump to next parameter */
+					}
+				} else if   (function_call_param_iterator_c::assign_out == call_param_dir) {
+					if ((function_param_iterator_c::direction_out   != param_dir)) {
+						function_invocation_error = true;
+						STAGE3_ERROR(0, param_name, param_name, "Invalid assignment syntax '=>' used for parameter '%s', when invoking %s '%s'", ((identifier_c *)param_name)->value, POU_str, ((identifier_c *)fcall_data.function_name)->value);
+						continue; /* jump to next parameter */
+					}
+				} else ERROR;
+
+				if (NULL == param_value->datatype) {
+					function_invocation_error = true;
+					STAGE3_ERROR(0, param_value, param_value, "Data type incompatibility between parameter '%s' and value being passed, when invoking %s '%s'", ((identifier_c *)param_name)->value, POU_str, ((identifier_c *)fcall_data.function_name)->value);
+					continue; /* jump to next parameter */
+				}
+			}
+		}
+	}
+	if (NULL != fcall_data.nonformal_operand_list) {
+		fcall_data.nonformal_operand_list->accept(*this);
+		if (f_decl)
+			for (int i = 1; (param_value = fcp_iterator.next_nf()) != NULL; i++) {
+		  		/* TODO: verify if it is lvalue when INOUT or OUTPUT parameters! */
+
+				/* This handle_function_invocation() will be called to handle IL function calls, where the first parameter comes from the previous IL instruction.
+				 * In this case, the previous IL instruction will be artifically (and temporarily) added to the begining ot the parameter list
+				 * so we (in this function) can handle this situation like all the other function calls.
+				 * However, 
+				 *     a) if NO previous IL function exists, then we get a fake previous IL function, with no location data (i.e. not found anywhere in the source code.
+				 *     b) the function call may actually have several prev IL instructions (if several JMP instructions jump directly to the il function call).
+				 * In order to handle these situations gracefully, we first check whether the first parameter is really an IL istruction!
+				 */
+				il_instruction_c *il_instruction_symbol = dynamic_cast<il_instruction_c *>(param_value);
+				if ((NULL != il_instruction_symbol) && (i == 1)) {
+					/* We are in a situation where an IL function call is passed the first parameter, which is actually the previous IL instruction */
+					/* However, this is really a fake previous il instruction (see visit(il_instruction_c *) )
+					 * We will iterate through all the real previous IL instructions, and analyse each of them one by one */
+					if (il_instruction_symbol->prev_il_instruction.size() == 0) {
+						function_invocation_error = true;
+						STAGE3_ERROR(0, fcall, fcall, "No available data to pass to first parameter of IL function %s. Missing a previous LD instruction?", ((identifier_c *)fcall_data.function_name)->value);
+					}
+#if 0
+					/* NOTE: We currently comment out this code...
+					 * This does not currently work, since the narrow operation is currently done on the intersection 
+					 * of all the previous IL instructions, so we currently either accept them all, or none at all.
+					 * In order to be able to produce these user freindly error messages, we will need to update the 
+					 * narrow algorithm. We leave this untill somebody aks for it...
+					 * So, for now, we simply comment out this code.
+					 */
+					for (unsigned int p = 0; p < il_instruction_symbol->prev_il_instruction.size(); p++) {
+						symbol_c *value = il_instruction_symbol->prev_il_instruction[p];  
+						if (!is_type_valid(value->datatype)) {
+							function_invocation_error = true;
+							STAGE3_ERROR(0, fcall, fcall, "Data type incompatibility for value passed to first parameter when invoking function '%s'", ((identifier_c *)fcall_data.function_name)->value);
+							STAGE3_ERROR(0, value, value, "This is the IL instruction producing the incompatible data type to first parameter of function '%s'", ((identifier_c *)fcall_data.function_name)->value);
+						}
+					}
+#else
+					if (!is_type_valid(il_instruction_symbol->datatype)) {
+						function_invocation_error = true;
+						STAGE3_ERROR(0, fcall, fcall, "Data type incompatibility between value in IL 'accumulator' and first parameter of function '%s'", ((identifier_c *)fcall_data.function_name)->value);
+					}
+#endif
+					if (function_invocation_error)
+						/* when handling a IL function call, and an error is found in the first parameter, then we bug out and do not print out any more error messages. */
+						return;
+				}
+				else if (!is_type_valid(param_value->datatype)) {
+					function_invocation_error = true;
+					STAGE3_ERROR(0, param_value, param_value, "Data type incompatibility for value passed in position %d when invoking %s '%s'", i, POU_str, ((identifier_c *)fcall_data.function_name)->value);
+				}
+			}
+	}
+
+	if (NULL == fcall_data.called_function_declaration) {
+		function_invocation_error = true;
+		STAGE3_ERROR(0, fcall, fcall, "Unable to resolve which overloaded %s '%s' is being invoked.", POU_str, ((identifier_c *)fcall_data.function_name)->value);
+	}
+
+	if (function_invocation_error) {
+		/* No compatible function exists */
+		STAGE3_ERROR(2, fcall, fcall, "Invalid parameters when invoking %s '%s'", POU_str, ((identifier_c *)fcall_data.function_name)->value);
+	} 
+
+	return;
+}
+
+
+
+void *print_datatypes_error_c::handle_implicit_il_fb_invocation(const char *param_name, symbol_c *il_operator, symbol_c *called_fb_declaration) {
+	if (NULL == il_operand) {
+		STAGE3_ERROR(0, il_operator, il_operator, "Missing operand for FB call operator '%s'.", param_name);
+		return NULL;
+	}
+	il_operand->accept(*this);
+	
+	if (NULL == called_fb_declaration) {
+		STAGE3_ERROR(0, il_operator, il_operand, "Invalid FB call: operand is not a FB instance.");
+		return NULL;
+	}
+
+	if (fake_prev_il_instruction->prev_il_instruction.empty()) {
+		STAGE3_ERROR(0, il_operator, il_operand, "FB invocation operator '%s' must be preceded by a 'LD' (or equivalent) operator.", param_name);	
+		return NULL;
+	}
+
+	/* Find the corresponding parameter in function declaration */
+	function_param_iterator_c fp_iterator(called_fb_declaration);
+	if (NULL == fp_iterator.search(param_name)) {
+		/* TODO: must also check whther it is an IN parameter!! */
+		/* NOTE: although all standard FBs have the implicit FB calls defined as input parameters
+		*        (i.e., for all standard FBs, CLK, PT, IN, CU, CD, S1, R1, etc... is always an input parameter)
+		*        if a non-standard (i.e. a FB not defined in the standard library) FB is being called, then
+		*        this (CLK, PT, IN, CU, ...) parameter may just have been defined as OUT or INOUT,
+		*        which will not work for an implicit FB call!
+		*/
+		STAGE3_ERROR(0, il_operator, il_operand, "FB called by '%s' operator does not have a parameter named '%s'", param_name, param_name);	
+		return NULL;
+	}
+	if (!are_all_datatypes_of_prev_il_instructions_datatypes_equal(fake_prev_il_instruction)) {
+		STAGE3_ERROR(0, il_operator, il_operand, "Data type incompatibility between parameter '%s' and value being passed.", param_name);
+		return NULL;
+	}
+	
+
+	/* NOTE: The error_level currently being used for errors in variables/constants etc... is rather high.
+	 *       However, in the case of an implicit FB call, if the datatype of the operand == NULL, this may be
+	 *       the __only__ indication of an error! So we test it here again, to make sure thtis error will really
+	 *       be printed out!
+	 */
+	if (NULL == il_operand->datatype) {
+		/* Note: the case of (NULL == fb_declaration) was already caught above! */
+// 		if (NULL != fb_declaration) {
+			STAGE3_ERROR(0, il_operator, il_operator, "Invalid FB call: Datatype incompatibility between the FB's '%s' parameter and value being passed, or paramater '%s' is not a 'VAR_INPUT' parameter.", param_name, param_name);
+			return NULL;
+// 		}
+	}
+
+	return NULL;
+}
+
+
+/*********************/
+/* B 1.2 - Constants */
+/*********************/
+/******************************/
+/* B 1.2.1 - Numeric Literals */
+/******************************/
+void *print_datatypes_error_c::visit(real_c *symbol) {
+	if (symbol->candidate_datatypes.size() == 0) {
+		STAGE3_ERROR(0, symbol, symbol, "Numerical value exceeds range for ANY_REAL data type.");
+	} else if (NULL == symbol->datatype) {
+		STAGE3_ERROR(4, symbol, symbol, "ANY_REAL data type not valid in this location.");
+	}
+	return NULL;
+}
+
+void *print_datatypes_error_c::visit(integer_c *symbol) {
+	if (symbol->candidate_datatypes.size() == 0) {
+		STAGE3_ERROR(0, symbol, symbol, "Numerical value exceeds range for ANY_INT data type.");
+	} else if (NULL == symbol->datatype) {
+		STAGE3_ERROR(4, symbol, symbol, "ANY_INT data type not valid in this location.");
+	}
+	return NULL;
+}
+
+void *print_datatypes_error_c::visit(neg_real_c *symbol) {
+	if (symbol->candidate_datatypes.size() == 0) {
+		STAGE3_ERROR(0, symbol, symbol, "Numerical value exceeds range for ANY_REAL data type.");
+	} else if (NULL == symbol->datatype) {
+		STAGE3_ERROR(4, symbol, symbol, "ANY_REAL data type not valid in this location.");
+	}
+	return NULL;
+}
+
+void *print_datatypes_error_c::visit(neg_integer_c *symbol) {
+	if (symbol->candidate_datatypes.size() == 0) {
+		STAGE3_ERROR(0, symbol, symbol, "Numerical value exceeds range for ANY_INT data type.");
+	} else if (NULL == symbol->datatype) {
+		STAGE3_ERROR(4, symbol, symbol, "ANY_INT data type not valid in this location.");
+	}
+	return NULL;
+}
+
+void *print_datatypes_error_c::visit(binary_integer_c *symbol) {
+	if (symbol->candidate_datatypes.size() == 0) {
+		STAGE3_ERROR(0, symbol, symbol, "Numerical value exceeds range for ANY_INT data type.");
+	} else if (NULL == symbol->datatype) {
+		STAGE3_ERROR(4, symbol, symbol, "ANY_INT data type not valid in this location.");
+	}
+	return NULL;
+}
+
+void *print_datatypes_error_c::visit(octal_integer_c *symbol) {
+	if (symbol->candidate_datatypes.size() == 0) {
+		STAGE3_ERROR(0, symbol, symbol, "Numerical value exceeds range for ANY_INT data type.");
+	} else if (NULL == symbol->datatype) {
+		STAGE3_ERROR(4, symbol, symbol, "ANY_INT data type not valid in this location.");
+	}
+	return NULL;
+}
+
+void *print_datatypes_error_c::visit(hex_integer_c *symbol) {
+	if (symbol->candidate_datatypes.size() == 0) {
+		STAGE3_ERROR(0, symbol, symbol, "Numerical value exceeds range for ANY_INT data type.");
+	} else if (NULL == symbol->datatype) {
+		STAGE3_ERROR(4, symbol, symbol, "ANY_INT data type not valid in this location.");
+	}
+	return NULL;
+}
+
+void *print_datatypes_error_c::visit(integer_literal_c *symbol) {
+	if (symbol->candidate_datatypes.size() == 0) {
+		STAGE3_ERROR(0, symbol, symbol, "Numerical value exceeds range for %s data type.", elementary_type_c::to_string(symbol->type));
+	} else if (NULL == symbol->datatype) {
+		STAGE3_ERROR(4, symbol, symbol, "ANY_INT data type not valid in this location.");
+	}
+	return NULL;
+}
+
+void *print_datatypes_error_c::visit(real_literal_c *symbol) {
+	if (symbol->candidate_datatypes.size() == 0) {
+		STAGE3_ERROR(0, symbol, symbol, "Numerical value exceeds range for %s data type.", elementary_type_c::to_string(symbol->type));
+	} else if (NULL == symbol->datatype) {
+		STAGE3_ERROR(4, symbol, symbol, "ANY_REAL data type not valid in this location.");
+	}
+	return NULL;
+}
+
+void *print_datatypes_error_c::visit(bit_string_literal_c *symbol) {
+	if (symbol->candidate_datatypes.size() == 0) {
+		STAGE3_ERROR(0, symbol, symbol, "Numerical value exceeds range for %s data type.", elementary_type_c::to_string(symbol->type));
+	} else if (NULL == symbol->datatype) {
+		STAGE3_ERROR(4, symbol, symbol, "ANY_BIT data type not valid in this location.");
+	}
+	return NULL;
+}
+
+void *print_datatypes_error_c::visit(boolean_literal_c *symbol) {
+	if (symbol->candidate_datatypes.size() == 0) {
+		STAGE3_ERROR(0, symbol, symbol, "Value is not valid for %s data type.", elementary_type_c::to_string(symbol->type));
+	} else if (NULL == symbol->datatype) {
+		STAGE3_ERROR(4, symbol, symbol, "ANY_BOOL data type not valid in this location.");
+	}
+	return NULL;
+}
+
+void *print_datatypes_error_c::visit(boolean_true_c *symbol) {
+	if (symbol->candidate_datatypes.size() == 0) {
+		STAGE3_ERROR(0, symbol, symbol, "Value is not valid for ANY_BOOL data type.");
+	} else if (NULL == symbol->datatype) {
+		STAGE3_ERROR(4, symbol, symbol, "ANY_BOOL data type not valid in this location.");
+	}
+	return NULL;
+}
+
+void *print_datatypes_error_c::visit(boolean_false_c *symbol) {
+	if (symbol->candidate_datatypes.size() == 0) {
+		STAGE3_ERROR(0, symbol, symbol, "Value is not valid for ANY_BOOL data type.");
+	} else if (NULL == symbol->datatype) {
+		STAGE3_ERROR(4, symbol, symbol, "ANY_BOOL data type not valid in this location.");
+	}
+	return NULL;
+}
+
+/*******************************/
+/* B.1.2.2   Character Strings */
+/*******************************/
+void *print_datatypes_error_c::visit(double_byte_character_string_c *symbol) {
+	if (symbol->candidate_datatypes.size() == 0) {
+		STAGE3_ERROR(0, symbol, symbol, "Numerical value exceeds range for WSTRING data type.");
+	} else if (NULL == symbol->datatype) {
+		STAGE3_ERROR(4, symbol, symbol, "WSTRING data type not valid in this location.");
+	}
+	return NULL;
+}
+
+void *print_datatypes_error_c::visit(single_byte_character_string_c *symbol) {
+	if (symbol->candidate_datatypes.size() == 0) {
+		STAGE3_ERROR(0, symbol, symbol, "Numerical value exceeds range for STRING data type.");
+	} else if (NULL == symbol->datatype) {
+		STAGE3_ERROR(4, symbol, symbol, "STRING data type not valid in this location.");
+	}
+	return NULL;
+}
+
+/***************************/
+/* B 1.2.3 - Time Literals */
+/***************************/
+/************************/
+/* B 1.2.3.1 - Duration */
+/************************/
+void *print_datatypes_error_c::visit(duration_c *symbol) {
+	if (symbol->candidate_datatypes.size() == 0) {
+		STAGE3_ERROR(0, symbol, symbol, "Invalid syntax for TIME data type.");
+	} else if (NULL == symbol->datatype) {
+		STAGE3_ERROR(4, symbol, symbol, "TIME data type not valid in this location.");
+	}
+	return NULL;
+}
+
+/************************************/
+/* B 1.2.3.2 - Time of day and Date */
+/************************************/
+void *print_datatypes_error_c::visit(time_of_day_c *symbol) {
+	if (symbol->candidate_datatypes.size() == 0) {
+		STAGE3_ERROR(0, symbol, symbol, "Invalid syntax for TOD data type.");
+	} else if (NULL == symbol->datatype) {
+		STAGE3_ERROR(4, symbol, symbol, "TOD data type not valid in this location.");
+	}
+	return NULL;
+}
+
+void *print_datatypes_error_c::visit(date_c *symbol) {
+	if (symbol->candidate_datatypes.size() == 0) {
+		STAGE3_ERROR(0, symbol, symbol, "Invalid syntax for DATE data type.");
+	} else if (NULL == symbol->datatype) {
+		STAGE3_ERROR(4, symbol, symbol, "DATE data type not valid in this location.");
+	}
+	return NULL;
+}
+
+void *print_datatypes_error_c::visit(date_and_time_c *symbol) {
+	if (symbol->candidate_datatypes.size() == 0) {
+		STAGE3_ERROR(0, symbol, symbol, "Invalid syntax for DT data type.");
+	} else if (NULL == symbol->datatype) {
+		STAGE3_ERROR(4, symbol, symbol, "DT data type not valid in this location.");
+	}
+	return NULL;
+}
+
+/**********************/
+/* B 1.3 - Data types */
+/**********************/
+/********************************/
+/* B 1.3.3 - Derived data types */
+/********************************/
+void *print_datatypes_error_c::visit(simple_spec_init_c *symbol) {
+	if (!is_type_valid(symbol->simple_specification->datatype)) {
+		STAGE3_ERROR(0, symbol->simple_specification, symbol->simple_specification, "Invalid data type.");
+	} else if (NULL != symbol->constant) {
+		if (!is_type_valid(symbol->constant->datatype))
+			STAGE3_ERROR(0, symbol->constant, symbol->constant, "Initial value has incompatible data type.");
+	} else if (!is_type_valid(symbol->datatype)) {
+		ERROR; /* If we have an error here, then we must also have an error in one of
+		        * the two previous tests. If we reach this point, some strange error is ocurring!
+			*/
+	}
+	return NULL;
+}
+
+void *print_datatypes_error_c::visit(data_type_declaration_c *symbol) {
+	// TODO !!!
+	/* for the moment we must return NULL so semantic analysis of remaining code is not interrupted! */
+	return NULL;
+}
+
+void *print_datatypes_error_c::visit(enumerated_value_c *symbol) {
+	if (symbol->candidate_datatypes.size() == 0)
+		STAGE3_ERROR(0, symbol, symbol, "Ambiguous enumerate value or Variable not declared in this scope.");
+	return NULL;
+}
+
+
+/*********************/
+/* B 1.4 - Variables */
+/*********************/
+void *print_datatypes_error_c::visit(symbolic_variable_c *symbol) {
+	if (symbol->candidate_datatypes.size() == 0)
+		STAGE3_ERROR(0, symbol, symbol, "Variable not declared in this scope.");
+	return NULL;
+}
+
+/********************************************/
+/* B 1.4.1 - Directly Represented Variables */
+/********************************************/
+void *print_datatypes_error_c::visit(direct_variable_c *symbol) {
+	if (symbol->candidate_datatypes.size() == 0) ERROR;
+	if (!is_type_valid(symbol->datatype))
+		STAGE3_ERROR(4, symbol, symbol, "Direct variable has incompatible data type with expression.");
+	return NULL;
+}
+
+/*************************************/
+/* B 1.4.2 - Multi-element variables */
+/*************************************/
+/*  subscripted_variable '[' subscript_list ']' */
+// SYM_REF2(array_variable_c, subscripted_variable, subscript_list)
+void *print_datatypes_error_c::visit(array_variable_c *symbol) {
+	if (symbol->candidate_datatypes.size() == 0)
+		STAGE3_ERROR(0, symbol, symbol, "Array variable not declared in this scope.");
+	
+	/* recursively call the subscript list to print any errors in the expressions used in the subscript...*/
+	symbol->subscript_list->accept(*this);
+	return NULL;
+}
+
+/* subscript_list ',' subscript */
+// SYM_LIST(subscript_list_c)
+void *print_datatypes_error_c::visit(subscript_list_c *symbol) {
+	for (int i = 0; i < symbol->n; i++) {
+		int start_error_count = error_count;
+		symbol->elements[i]->accept(*this);
+		/* The following error message will only get printed if the current_display_error_level is set higher than 0! */
+		if ((start_error_count == error_count) && (NULL == symbol->elements[i]->datatype))
+			STAGE3_ERROR(0, symbol, symbol, "Invalid data type for array subscript field.");
+	}
+	return NULL;
+}
+
+
+/*  record_variable '.' field_selector */
+/*  WARNING: input and/or output variables of function blocks
+ *           may be accessed as fields of a structured variable!
+ *           Code handling a structured_variable_c must take
+ *           this into account!
+ */
+// SYM_REF2(structured_variable_c, record_variable, field_selector)
+/* NOTE: We do not recursively determine the data types of each field_selector in fill_candidate_datatypes_c,
+ * so it does not make sense to recursively visit all the field_selectors to print out error messages. 
+ * Maybe in the future, if we find the need to print out more detailed error messages, we might do it that way. For now, we don't!
+ */
+void *print_datatypes_error_c::visit(structured_variable_c *symbol) {
+	if (symbol->candidate_datatypes.size() == 0)
+		STAGE3_ERROR(0, symbol, symbol, "Undeclared structured/FB variable.");
+	return NULL;
+}
+
+
+
+/******************************************/
+/* B 1.4.3 - Declaration & Initialisation */
+/******************************************/
+
+/*  AT direct_variable */
+// SYM_REF1(location_c, direct_variable)
+void *print_datatypes_error_c::visit(location_c *symbol) {
+	symbol->direct_variable->accept(*this);
+	return NULL;
+}
+
+
+/*  [variable_name] location ':' located_var_spec_init */
+/* variable_name -> may be NULL ! */
+// SYM_REF3(located_var_decl_c, variable_name, location, located_var_spec_init)
+void *print_datatypes_error_c::visit(located_var_decl_c *symbol) {
+  symbol->located_var_spec_init->accept(*this);
+  /* It does not make sense to call symbol->location->accept(*this). The check is done right here if the following if() */
+  // symbol->location->accept(*this); 
+  if ((is_type_valid(symbol->located_var_spec_init->datatype)) && (!is_type_valid(symbol->location->datatype)))
+    STAGE3_ERROR(0, symbol, symbol, "Bit size of data type is incompatible with bit size of location.");
+  return NULL;
+}  
+
+
+/************************************/
+/* B 1.5 Program organization units */
+/************************************/
+/*********************/
+/* B 1.5.1 Functions */
+/*********************/
+void *print_datatypes_error_c::visit(function_declaration_c *symbol) {
+	search_varfb_instance_type = new search_varfb_instance_type_c(symbol);
+	/* We do not check for data type errors in variable declarations, Skip this for now... */
+// 	symbol->var_declarations_list->accept(*this);
+	if (debug) printf("Print error data types list in body of function %s\n", ((token_c *)(symbol->derived_function_name))->value);
+	il_parenthesis_level = 0;
+	il_error = false;
+	symbol->function_body->accept(*this);
+	delete search_varfb_instance_type;
+	search_varfb_instance_type = NULL;
+	return NULL;
+}
+
+/***************************/
+/* B 1.5.2 Function blocks */
+/***************************/
+void *print_datatypes_error_c::visit(function_block_declaration_c *symbol) {
+	search_varfb_instance_type = new search_varfb_instance_type_c(symbol);
+	/* We do not check for data type errors in variable declarations, Skip this for now... */
+// 	symbol->var_declarations->accept(*this);
+	if (debug) printf("Print error data types list in body of FB %s\n", ((token_c *)(symbol->fblock_name))->value);
+	il_parenthesis_level = 0;
+	il_error = false;
+	symbol->fblock_body->accept(*this);
+	delete search_varfb_instance_type;
+	search_varfb_instance_type = NULL;
+	return NULL;
+}
+
+/**********************/
+/* B 1.5.3 - Programs */
+/**********************/
+void *print_datatypes_error_c::visit(program_declaration_c *symbol) {
+	search_varfb_instance_type = new search_varfb_instance_type_c(symbol);
+	/* We do not check for data type errors in variable declarations, Skip this for now... */
+	symbol->var_declarations->accept(*this);
+	if (debug) printf("Print error data types list in body of program %s\n", ((token_c *)(symbol->program_type_name))->value);
+	il_parenthesis_level = 0;
+	il_error = false;
+	symbol->function_block_body->accept(*this);
+	delete search_varfb_instance_type;
+	search_varfb_instance_type = NULL;
+	return NULL;
+}
+
+
+
+/********************************/
+/* B 1.7 Configuration elements */
+/********************************/
+void *print_datatypes_error_c::visit(configuration_declaration_c *symbol) {
+	// TODO !!!
+	/* for the moment we must return NULL so semantic analysis of remaining code is not interrupted! */
+	return NULL;
+}
+
+/****************************************/
+/* B.2 - Language IL (Instruction List) */
+/****************************************/
+/***********************************/
+/* B 2.1 Instructions and Operands */
+/***********************************/
+
+// void *visit(instruction_list_c *symbol);
+
+/* | label ':' [il_incomplete_instruction] eol_list */
+// SYM_REF2(il_instruction_c, label, il_instruction)
+void *print_datatypes_error_c::visit(il_instruction_c *symbol) {
+	if (NULL != symbol->il_instruction) {
+		il_instruction_c tmp_prev_il_instruction(NULL, NULL);
+#if 0
+		/* NOTE: The following is currently no longer needed. Since the following code is actually cool, 
+		 * we don't delete it, but simply comment it out. It might just come in handy later on...
+		 */
+		/* When handling a il function call, this fake_prev_il_instruction may be used as a standard function call parameter, so it is important that 
+		 * it contain some valid location info so error messages make sense.
+		 */
+		if (symbol->prev_il_instruction.size() > 0) {
+			/* since we don't want to copy all that data one variable at a time, we copy it all at once */
+			/* This has the advantage that, if we ever add some more data to the base symbol_c later on, we will not need to
+			 * change the following line to guarantee that the data is copied correctly!
+			 * However, it does have the drawback of copying more data than what we want!
+			 * In order to only copy the data in the base class symbol_c, we use the tmp_symbol pointer!
+			 * I (mario) have checked with a debugger, and it is working as intended!
+			 */
+			symbol_c *tmp_symbol1 = symbol->prev_il_instruction[0];
+			symbol_c *tmp_symbol2 = &tmp_prev_il_instruction;
+			*tmp_symbol2 = *tmp_symbol1;
+			/* we do not want to copy the datatype variable, so we reset it to NULL */
+			tmp_prev_il_instruction.datatype = NULL;
+			/* We don't need to worry about the candidate_datatype list (which we don't want to copy just yet), since that will 
+			 * be reset to the correct value when we call intersect_prev_candidate_datatype_lists() later on...
+			 */
+		}
+#endif
+		/* the print error algorithm will need access to the intersected candidate_datatype lists of all prev_il_instructions, as well as the 
+		 * list of the prev_il_instructions.
+		 * Instead of creating two 'global' (within the class) variables, we create a single il_instruction_c variable (fake_prev_il_instruction),
+		 * and shove that data into this single variable.
+		 */
+		tmp_prev_il_instruction.prev_il_instruction = symbol->prev_il_instruction;
+		intersect_prev_candidate_datatype_lists(&tmp_prev_il_instruction);
+		if (are_all_datatypes_of_prev_il_instructions_datatypes_equal(symbol))
+			if (symbol->prev_il_instruction.size() > 0)
+				tmp_prev_il_instruction.datatype = (symbol->prev_il_instruction[0])->datatype;
+		
+		/* Tell the il_instruction the datatype that it must generate - this was chosen by the next il_instruction (remember: we are iterating backwards!) */
+		fake_prev_il_instruction = &tmp_prev_il_instruction;
+		symbol->il_instruction->accept(*this);
+		fake_prev_il_instruction = NULL;
+	}
+
+	return NULL;
+}
+
+
+
+void *print_datatypes_error_c::visit(il_simple_operation_c *symbol) {
+	il_operand = symbol->il_operand;
+	if (NULL != symbol->il_operand) {
+		symbol->il_operand->accept(*this);
+	}
+	/* recursive call to see whether data types are compatible */
+	symbol->il_simple_operator->accept(*this);
+	il_operand = NULL;
+	return NULL;
+}
+
+/* | function_name [il_operand_list] */
+/* NOTE: The parameters 'called_function_declaration' and 'extensible_param_count' are used to pass data between the stage 3 and stage 4. */
+// SYM_REF2(il_function_call_c, function_name, il_operand_list, symbol_c *called_function_declaration; int extensible_param_count;)
+void *print_datatypes_error_c::visit(il_function_call_c *symbol) {
+	/* The first parameter of a non formal function call in IL will be the 'current value' (i.e. the prev_il_instruction)
+	 * In order to be able to handle this without coding special cases, we will simply prepend that symbol
+	 * to the il_operand_list, and remove it after calling handle_function_call().
+	 *
+	 * However, if no further paramters are given, then il_operand_list will be NULL, and we will
+	 * need to create a new object to hold the pointer to prev_il_instruction.
+	 * This change will also be undone later in print_datatypes_error_c.
+	 */
+	if (NULL == symbol->il_operand_list)  symbol->il_operand_list = new il_operand_list_c;
+	if (NULL == symbol->il_operand_list)  ERROR;
+
+	((list_c *)symbol->il_operand_list)->insert_element(fake_prev_il_instruction, 0);
+
+	generic_function_call_t fcall_param = {
+		/* fcall_param.function_name               = */ symbol->function_name,
+		/* fcall_param.nonformal_operand_list      = */ symbol->il_operand_list,
+		/* fcall_param.formal_operand_list         = */ NULL,
+		/* enum {POU_FB, POU_function} POU_type    = */ generic_function_call_t::POU_function,
+		/* fcall_param.candidate_functions         = */ symbol->candidate_functions,
+		/* fcall_param.called_function_declaration = */ symbol->called_function_declaration,
+		/* fcall_param.extensible_param_count      = */ symbol->extensible_param_count
+	};
+
+/* TODO: check what error message (if any) the compiler will give out if this function invocation
+ * is not preceded by a LD operator (or another equivalent operator or list of operators).
+ */
+	handle_function_invocation(symbol, fcall_param);
+	
+	/* We now undo those changes to the abstract syntax tree made above! */
+	((list_c *)symbol->il_operand_list)->remove_element(0);
+	if (((list_c *)symbol->il_operand_list)->n == 0) {
+		/* if the list becomes empty, then that means that it did not exist before we made these changes, so we delete it! */
+		delete 	symbol->il_operand_list;
+		symbol->il_operand_list = NULL;
+	}
+
+	return NULL;
+}
+
+
+/* | il_expr_operator '(' [il_operand] eol_list [simple_instr_list] ')' */
+// SYM_REF3(il_expression_c, il_expr_operator, il_operand, simple_instr_list);
+void *print_datatypes_error_c::visit(il_expression_c *symbol) {
+  /* first give the parenthesised IL list a chance to print errors */
+  il_instruction_c *save_fake_prev_il_instruction = fake_prev_il_instruction;
+  symbol->simple_instr_list->accept(*this);
+  fake_prev_il_instruction = save_fake_prev_il_instruction;
+
+  /* Now handle the operation (il_expr_operator) that will use the result coming from the parenthesised IL list (i.e. simple_instr_list) */
+  il_operand = symbol->simple_instr_list; /* This is not a bug! The parenthesised expression will be used as the operator! */
+  symbol->il_expr_operator->accept(*this);
+
+return NULL;
+}
+
+
+/*   il_call_operator prev_declared_fb_name
+ * | il_call_operator prev_declared_fb_name '(' ')'
+ * | il_call_operator prev_declared_fb_name '(' eol_list ')'
+ * | il_call_operator prev_declared_fb_name '(' il_operand_list ')'
+ * | il_call_operator prev_declared_fb_name '(' eol_list il_param_list ')'
+ */
+/* NOTE: The parameter 'called_fb_declaration'is used to pass data between stage 3 and stage4 (although currently it is not used in stage 4 */
+// SYM_REF4(il_fb_call_c, il_call_operator, fb_name, il_operand_list, il_param_list, symbol_c *called_fb_declaration)
+void *print_datatypes_error_c::visit(il_fb_call_c *symbol) {
+	int extensible_param_count;                      /* unused vairable! Needed for compilation only! */
+	std::vector <symbol_c *> candidate_functions;    /* unused vairable! Needed for compilation only! */
+	generic_function_call_t fcall_param = {
+		/* fcall_param.function_name               = */ symbol->fb_name,
+		/* fcall_param.nonformal_operand_list      = */ symbol->il_operand_list,
+		/* fcall_param.formal_operand_list         = */ symbol->il_param_list,
+		/* enum {POU_FB, POU_function} POU_type    = */ generic_function_call_t::POU_FB,
+		/* fcall_param.candidate_functions         = */ candidate_functions,             /* will not be used, but must provide a reference to be able to compile */
+		/* fcall_param.called_function_declaration = */ symbol->called_fb_declaration,
+		/* fcall_param.extensible_param_count      = */ extensible_param_count           /* will not be used, but must provide a reference to be able to compile */
+	};
+  
+	handle_function_invocation(symbol, fcall_param);
+	/* check the semantics of the CALC, CALCN operators! */
+	symbol->il_call_operator->accept(*this);
+	return NULL;
+}
+
+/* | function_name '(' eol_list [il_param_list] ')' */
+/* NOTE: The parameter 'called_function_declaration' is used to pass data between the stage 3 and stage 4. */
+// SYM_REF2(il_formal_funct_call_c, function_name, il_param_list, symbol_c *called_function_declaration; int extensible_param_count;)
+void *print_datatypes_error_c::visit(il_formal_funct_call_c *symbol) {
+	generic_function_call_t fcall_param = {
+		/* fcall_param.function_name               = */ symbol->function_name,
+		/* fcall_param.nonformal_operand_list      = */ NULL,
+		/* fcall_param.formal_operand_list         = */ symbol->il_param_list,
+		/* enum {POU_FB, POU_function} POU_type    = */ generic_function_call_t::POU_function,
+		/* fcall_param.candidate_functions         = */ symbol->candidate_functions,
+		/* fcall_param.called_function_declaration = */ symbol->called_function_declaration,
+		/* fcall_param.extensible_param_count      = */ symbol->extensible_param_count
+	};
+  
+	handle_function_invocation(symbol, fcall_param);
+	return NULL;
+}
+
+
+//     void *visit(il_operand_list_c *symbol);
+//     void *visit(simple_instr_list_c *symbol);
+
+// SYM_REF1(il_simple_instruction_c, il_simple_instruction, symbol_c *prev_il_instruction;)
+void *print_datatypes_error_c::visit(il_simple_instruction_c *symbol)	{
+  if (symbol->prev_il_instruction.size() > 1) ERROR; /* There should be no labeled insructions inside an IL expression! */
+    
+  il_instruction_c tmp_prev_il_instruction(NULL, NULL);
+  /* the print error algorithm will need access to the intersected candidate_datatype lists of all prev_il_instructions, as well as the 
+   * list of the prev_il_instructions.
+   * Instead of creating two 'global' (within the class) variables, we create a single il_instruction_c variable (fake_prev_il_instruction),
+   * and shove that data into this single variable.
+   */
+  if (symbol->prev_il_instruction.size() > 0)
+    tmp_prev_il_instruction.candidate_datatypes = symbol->prev_il_instruction[0]->candidate_datatypes;
+  tmp_prev_il_instruction.prev_il_instruction = symbol->prev_il_instruction;
+  
+   /* copy the candidate_datatypes list */
+  fake_prev_il_instruction = &tmp_prev_il_instruction;
+  symbol->il_simple_instruction->accept(*this);
+  fake_prev_il_instruction = NULL;
+  return NULL;
+  
+  
+//   if (symbol->prev_il_instruction.size() == 0)  prev_il_instruction = NULL;
+//   else                                          prev_il_instruction = symbol->prev_il_instruction[0];
+
+//   symbol->il_simple_instruction->accept(*this);
+//   prev_il_instruction = NULL;
+//   return NULL;
+}
+
+
+//     void *visit(il_param_list_c *symbol);
+//     void *visit(il_param_assignment_c *symbol);
+//     void *visit(il_param_out_assignment_c *symbol);
+
+/*******************/
+/* B 2.2 Operators */
+/*******************/
+void *print_datatypes_error_c::print_binary_operator_errors(const char *il_operator, symbol_c *symbol, bool deprecated_operation) {
+	if ((symbol->candidate_datatypes.size() == 0) && (il_operand->candidate_datatypes.size() > 0)) {
+		STAGE3_ERROR(0, symbol, symbol, "Data type mismatch for '%s' operator.", il_operator);
+	} else if (NULL == symbol->datatype) {
+		STAGE3_WARNING(symbol, symbol, "Result of '%s' operation is never used.", il_operator);
+	} else if (deprecated_operation)
+		STAGE3_WARNING(symbol, symbol, "Deprecated operation for '%s' operator.", il_operator);
+	return NULL;
+}
+
+
+void *print_datatypes_error_c::visit(LD_operator_c *symbol) {
+	return NULL;
+}
+
+void *print_datatypes_error_c::visit(LDN_operator_c *symbol) {
+	if ((symbol->candidate_datatypes.size() == 0) 		&&
+		(il_operand->candidate_datatypes.size() > 0))
+		STAGE3_ERROR(0, symbol, symbol, "Data type mismatch for 'LDN' operator.");
+	return NULL;
+}
+
+void *print_datatypes_error_c::visit(ST_operator_c *symbol) {
+	/* MANU:
+	 * if prev_instruction is NULL we can print a message error or warning error like:
+	 * we can't use a ST like first instruction.
+	 * What do you think?
+	 */
+	if ((symbol->candidate_datatypes.size() == 0) 		&&
+		(il_operand->candidate_datatypes.size() > 0))
+		STAGE3_ERROR(0, symbol, symbol, "Data type mismatch for 'ST' operator.");
+	return NULL;
+}
+
+void *print_datatypes_error_c::visit(STN_operator_c *symbol) {
+	/* MANU:
+	 * if prev_instruction is NULL we can print a message error or warning error like:
+	 * we can't use a ST like first instruction.
+	 * What do you think?
+	 */
+	if ((symbol->candidate_datatypes.size() == 0) 		&&
+		(il_operand->candidate_datatypes.size() > 0))
+		STAGE3_ERROR(0, symbol, symbol, "Data type mismatch for 'STN' operator.");
+	return NULL;
+}
+
+void *print_datatypes_error_c::visit(NOT_operator_c *symbol) {
+	/* NOTE: the standard allows syntax in which the NOT operator is followed by an optional <il_operand>
+	 *              NOT [<il_operand>]
+	 *       However, it does not define the semantic of the NOT operation when the <il_operand> is specified.
+	 *       We therefore consider it an error if an il_operand is specified!
+	 */
+	if (il_operand != NULL)
+		STAGE3_ERROR(0, symbol, symbol, "'NOT' operator may not have an operand.");
+	if (symbol->candidate_datatypes.size() == 0)
+		STAGE3_ERROR(0, symbol, symbol, "Data type mismatch for 'NOT' operator.");
+	return NULL;
+}
+
+void *print_datatypes_error_c::visit(S_operator_c *symbol) {
+  /* TODO: what if this is a FB call ?? */
+	if ((symbol->candidate_datatypes.size() == 0) 		&&
+		(il_operand->candidate_datatypes.size() > 0))
+		STAGE3_ERROR(0, symbol, symbol, "Data type mismatch for 'S' operator.");
+	return NULL;
+}
+
+void *print_datatypes_error_c::visit(R_operator_c *symbol) {
+  /* TODO: what if this is a FB call ?? */
+	if ((symbol->candidate_datatypes.size() == 0) 		&&
+		(il_operand->candidate_datatypes.size() > 0))
+		STAGE3_ERROR(0, symbol, symbol, "Data type mismatch for 'R' operator.");
+	return NULL;
+}
+
+void *print_datatypes_error_c::visit( S1_operator_c *symbol) {return handle_implicit_il_fb_invocation( "S1", symbol, symbol->called_fb_declaration);}
+void *print_datatypes_error_c::visit( R1_operator_c *symbol) {return handle_implicit_il_fb_invocation( "R1", symbol, symbol->called_fb_declaration);}
+void *print_datatypes_error_c::visit(CLK_operator_c *symbol) {return handle_implicit_il_fb_invocation("CLK", symbol, symbol->called_fb_declaration);}
+void *print_datatypes_error_c::visit( CU_operator_c *symbol) {return handle_implicit_il_fb_invocation( "CU", symbol, symbol->called_fb_declaration);}
+void *print_datatypes_error_c::visit( CD_operator_c *symbol) {return handle_implicit_il_fb_invocation( "CD", symbol, symbol->called_fb_declaration);}
+void *print_datatypes_error_c::visit( PV_operator_c *symbol) {return handle_implicit_il_fb_invocation( "PV", symbol, symbol->called_fb_declaration);}
+void *print_datatypes_error_c::visit( IN_operator_c *symbol) {return handle_implicit_il_fb_invocation( "IN", symbol, symbol->called_fb_declaration);}
+void *print_datatypes_error_c::visit( PT_operator_c *symbol) {return handle_implicit_il_fb_invocation( "PT", symbol, symbol->called_fb_declaration);}
+
+void *print_datatypes_error_c::visit( AND_operator_c *symbol) {return print_binary_operator_errors("AND" , symbol);}
+void *print_datatypes_error_c::visit(  OR_operator_c *symbol) {return print_binary_operator_errors( "OR" , symbol);}
+void *print_datatypes_error_c::visit( XOR_operator_c *symbol) {return print_binary_operator_errors("XOR" , symbol);}
+void *print_datatypes_error_c::visit(ANDN_operator_c *symbol) {return print_binary_operator_errors("ANDN", symbol);}
+void *print_datatypes_error_c::visit( ORN_operator_c *symbol) {return print_binary_operator_errors( "ORN", symbol);}
+void *print_datatypes_error_c::visit(XORN_operator_c *symbol) {return print_binary_operator_errors("XORN", symbol);}
+void *print_datatypes_error_c::visit( ADD_operator_c *symbol) {return print_binary_operator_errors("ADD" , symbol, symbol->deprecated_operation);}
+void *print_datatypes_error_c::visit( SUB_operator_c *symbol) {return print_binary_operator_errors("SUB" , symbol, symbol->deprecated_operation);}
+void *print_datatypes_error_c::visit( MUL_operator_c *symbol) {return print_binary_operator_errors("MUL" , symbol, symbol->deprecated_operation);}
+void *print_datatypes_error_c::visit( DIV_operator_c *symbol) {return print_binary_operator_errors("DIV" , symbol, symbol->deprecated_operation);}
+void *print_datatypes_error_c::visit( MOD_operator_c *symbol) {return print_binary_operator_errors("MOD" , symbol);}
+
+void *print_datatypes_error_c::visit(  GT_operator_c *symbol) {return print_binary_operator_errors( "GT" , symbol);}
+void *print_datatypes_error_c::visit(  GE_operator_c *symbol) {return print_binary_operator_errors( "GE" , symbol);}
+void *print_datatypes_error_c::visit(  EQ_operator_c *symbol) {return print_binary_operator_errors( "EQ" , symbol);}
+void *print_datatypes_error_c::visit(  LT_operator_c *symbol) {return print_binary_operator_errors( "LT" , symbol);}
+void *print_datatypes_error_c::visit(  LE_operator_c *symbol) {return print_binary_operator_errors( "LE" , symbol);}
+void *print_datatypes_error_c::visit(  NE_operator_c *symbol) {return print_binary_operator_errors( "NE" , symbol);}
+
+  
+
+
+void *print_datatypes_error_c::handle_conditional_flow_control_IL_instruction(symbol_c *symbol, const char *oper) {
+	if (NULL == symbol->datatype)
+		STAGE3_ERROR(0, symbol, symbol, "%s operator must be preceded by an IL instruction producing a BOOL value.", oper);
+	return NULL;
+}
+
+void *print_datatypes_error_c::visit(  CAL_operator_c *symbol) {return NULL;}
+void *print_datatypes_error_c::visit( CALC_operator_c *symbol) {return handle_conditional_flow_control_IL_instruction(symbol, "CALC" );}
+void *print_datatypes_error_c::visit(CALCN_operator_c *symbol) {return handle_conditional_flow_control_IL_instruction(symbol, "CALCN");}
+void *print_datatypes_error_c::visit(  RET_operator_c *symbol) {return NULL;}
+void *print_datatypes_error_c::visit( RETC_operator_c *symbol) {return handle_conditional_flow_control_IL_instruction(symbol, "RETC" );}
+void *print_datatypes_error_c::visit(RETCN_operator_c *symbol) {return handle_conditional_flow_control_IL_instruction(symbol, "RETCN");}
+void *print_datatypes_error_c::visit(  JMP_operator_c *symbol) {return NULL;}
+void *print_datatypes_error_c::visit( JMPC_operator_c *symbol) {return handle_conditional_flow_control_IL_instruction(symbol, "JMPC" );}
+void *print_datatypes_error_c::visit(JMPCN_operator_c *symbol) {return handle_conditional_flow_control_IL_instruction(symbol, "JMPCN");}
+
+
+
+/* Symbol class handled together with function call checks */
+// void *visit(il_assign_operator_c *symbol, variable_name);
+/* Symbol class handled together with function call checks */
+// void *visit(il_assign_operator_c *symbol, option, variable_name);
+
+/***************************************/
+/* B.3 - Language ST (Structured Text) */
+/***************************************/
+/***********************/
+/* B 3.1 - Expressions */
+/***********************/
+
+void *print_datatypes_error_c::print_binary_expression_errors(const char *operation, symbol_c *symbol, symbol_c *l_expr, symbol_c *r_expr, bool deprecated_operation) {
+	l_expr->accept(*this);
+	r_expr->accept(*this);
+	if ((symbol->candidate_datatypes.size() == 0) 		&&
+		(l_expr->candidate_datatypes.size() > 0)	&&
+		(r_expr->candidate_datatypes.size() > 0))
+		STAGE3_ERROR(0, symbol, symbol, "Data type mismatch for '%s' expression.", operation);
+        if (deprecated_operation)
+                STAGE3_WARNING(symbol, symbol, "Deprecated operation for '%s' expression.", operation);
+	return NULL;
+}
+
+
+void *print_datatypes_error_c::visit(    or_expression_c *symbol) {return print_binary_expression_errors( "OR", symbol, symbol->l_exp, symbol->r_exp);}
+void *print_datatypes_error_c::visit(   xor_expression_c *symbol) {return print_binary_expression_errors("XOR", symbol, symbol->l_exp, symbol->r_exp);}
+void *print_datatypes_error_c::visit(   and_expression_c *symbol) {return print_binary_expression_errors("AND", symbol, symbol->l_exp, symbol->r_exp);}
+void *print_datatypes_error_c::visit(   equ_expression_c *symbol) {return print_binary_expression_errors( "=" , symbol, symbol->l_exp, symbol->r_exp);}
+void *print_datatypes_error_c::visit(notequ_expression_c *symbol) {return print_binary_expression_errors( "<>", symbol, symbol->l_exp, symbol->r_exp);}
+void *print_datatypes_error_c::visit(    lt_expression_c *symbol) {return print_binary_expression_errors( "<" , symbol, symbol->l_exp, symbol->r_exp);}
+void *print_datatypes_error_c::visit(    gt_expression_c *symbol) {return print_binary_expression_errors( ">" , symbol, symbol->l_exp, symbol->r_exp);}
+void *print_datatypes_error_c::visit(    le_expression_c *symbol) {return print_binary_expression_errors( "<=", symbol, symbol->l_exp, symbol->r_exp);}
+void *print_datatypes_error_c::visit(    ge_expression_c *symbol) {return print_binary_expression_errors( ">=", symbol, symbol->l_exp, symbol->r_exp);}
+void *print_datatypes_error_c::visit(   add_expression_c *symbol) {return print_binary_expression_errors( "+" , symbol, symbol->l_exp, symbol->r_exp, symbol->deprecated_operation);}
+void *print_datatypes_error_c::visit(   sub_expression_c *symbol) {return print_binary_expression_errors( "-" , symbol, symbol->l_exp, symbol->r_exp, symbol->deprecated_operation);}
+void *print_datatypes_error_c::visit(   mul_expression_c *symbol) {return print_binary_expression_errors( "*" , symbol, symbol->l_exp, symbol->r_exp, symbol->deprecated_operation);}
+void *print_datatypes_error_c::visit(   div_expression_c *symbol) {return print_binary_expression_errors( "/" , symbol, symbol->l_exp, symbol->r_exp, symbol->deprecated_operation);}
+void *print_datatypes_error_c::visit(   mod_expression_c *symbol) {return print_binary_expression_errors("MOD", symbol, symbol->l_exp, symbol->r_exp);}
+void *print_datatypes_error_c::visit( power_expression_c *symbol) {return print_binary_expression_errors( "**", symbol, symbol->l_exp, symbol->r_exp);}
+
+
+void *print_datatypes_error_c::visit(neg_expression_c *symbol) {
+	symbol->exp->accept(*this);
+	if ((symbol->candidate_datatypes.size() == 0)      &&
+		(symbol->exp->candidate_datatypes.size() > 0))
+		STAGE3_ERROR(0, symbol, symbol, "Invalid data type for 'NEG' expression.");
+	return NULL;
+}
+
+
+void *print_datatypes_error_c::visit(not_expression_c *symbol) {
+	symbol->exp->accept(*this);
+	if ((symbol->candidate_datatypes.size() == 0)      &&
+		(symbol->exp->candidate_datatypes.size() > 0))
+		STAGE3_ERROR(0, symbol, symbol, "Invalid data type for 'NOT' expression.");
+	return NULL;
+}
+
+/* NOTE: The parameter 'called_function_declaration', 'extensible_param_count' and 'candidate_functions' are used to pass data between the stage 3 and stage 4. */
+/*    formal_param_list -> may be NULL ! */
+/* nonformal_param_list -> may be NULL ! */
+// SYM_REF3(function_invocation_c, function_name, formal_param_list, nonformal_param_list, symbol_c *called_function_declaration; int extensible_param_count; std::vector <symbol_c *> candidate_functions;)
+void *print_datatypes_error_c::visit(function_invocation_c *symbol) {
+	generic_function_call_t fcall_param = {
+		/* fcall_param.function_name               = */ symbol->function_name,
+		/* fcall_param.nonformal_operand_list      = */ symbol->nonformal_param_list,
+		/* fcall_param.formal_operand_list         = */ symbol->formal_param_list,
+		/* enum {POU_FB, POU_function} POU_type    = */ generic_function_call_t::POU_function,
+		/* fcall_param.candidate_functions         = */ symbol->candidate_functions,
+		/* fcall_param.called_function_declaration = */ symbol->called_function_declaration,
+		/* fcall_param.extensible_param_count      = */ symbol->extensible_param_count
+	};
+
+	handle_function_invocation(symbol, fcall_param);
+	return NULL;
+}
+
+
+
+/********************/
+/* B 3.2 Statements */
+/********************/
+
+/*********************************/
+/* B 3.2.1 Assignment Statements */
+/*********************************/
+void *print_datatypes_error_c::visit(assignment_statement_c *symbol) {
+	symbol->l_exp->accept(*this);
+	symbol->r_exp->accept(*this);
+	if ((NULL == symbol->l_exp->datatype) &&
+	    (NULL == symbol->r_exp->datatype) &&
+		(symbol->l_exp->candidate_datatypes.size() > 0)	&&
+		(symbol->r_exp->candidate_datatypes.size() > 0))
+		STAGE3_ERROR(0, symbol, symbol, "Incompatible data types for ':=' operation.");
+	return NULL;
+}
+
+
+/*****************************************/
+/* B 3.2.2 Subprogram Control Statements */
+/*****************************************/
+/* fb_name '(' [param_assignment_list] ')' */
+/*    formal_param_list -> may be NULL ! */
+/* nonformal_param_list -> may be NULL ! */
+/* NOTE: The parameter 'called_fb_declaration'is used to pass data between stage 3 and stage4 (although currently it is not used in stage 4 */
+// SYM_REF3(fb_invocation_c, fb_name, formal_param_list, nonformal_param_list, symbol_c *called_fb_declaration;)
+void *print_datatypes_error_c::visit(fb_invocation_c *symbol) {
+	int extensible_param_count;                      /* unused vairable! Needed for compilation only! */
+	std::vector <symbol_c *> candidate_functions;    /* unused vairable! Needed for compilation only! */
+	generic_function_call_t fcall_param = {
+		/* fcall_param.function_name               = */ symbol->fb_name,
+		/* fcall_param.nonformal_operand_list      = */ symbol->nonformal_param_list,
+		/* fcall_param.formal_operand_list         = */ symbol->formal_param_list,
+		/* enum {POU_FB, POU_function} POU_type    = */ generic_function_call_t::POU_FB,
+		/* fcall_param.candidate_functions         = */ candidate_functions,             /* will not be used, but must provide a reference to be able to compile */
+		/* fcall_param.called_function_declaration = */ symbol->called_fb_declaration,
+		/* fcall_param.extensible_param_count      = */ extensible_param_count           /* will not be used, but must provide a reference to be able to compile */
+	};
+	
+	handle_function_invocation(symbol, fcall_param);
+	return NULL;
+}
+
+
+/********************************/
+/* B 3.2.3 Selection Statements */
+/********************************/
+
+void *print_datatypes_error_c::visit(if_statement_c *symbol) {
+	symbol->expression->accept(*this);
+	if ((NULL == symbol->expression->datatype) &&
+		(symbol->expression->candidate_datatypes.size() > 0)) {
+		STAGE3_ERROR(0, symbol, symbol, "Invalid data type for 'IF' condition.");
+	}
+	if (NULL != symbol->statement_list)
+		symbol->statement_list->accept(*this);
+	if (NULL != symbol->elseif_statement_list)
+		symbol->elseif_statement_list->accept(*this);
+	if (NULL != symbol->else_statement_list)
+		symbol->else_statement_list->accept(*this);
+	return NULL;
+}
+
+void *print_datatypes_error_c::visit(elseif_statement_c *symbol) {
+	symbol->expression->accept(*this);
+	if ((NULL == symbol->expression->datatype) &&
+		(symbol->expression->candidate_datatypes.size() > 0)) {
+		STAGE3_ERROR(0, symbol, symbol, "Invalid data type for 'ELSIF' condition.");
+	}
+	if (NULL != symbol->statement_list)
+		symbol->statement_list->accept(*this);
+	return NULL;
+}
+
+
+void *print_datatypes_error_c::visit(case_statement_c *symbol) {
+	symbol->expression->accept(*this);
+	if ((NULL == symbol->expression->datatype) &&
+		(symbol->expression->candidate_datatypes.size() > 0)) {
+		STAGE3_ERROR(0, symbol, symbol, "'CASE' quantity not an integer or enumerated.");
+	}
+	symbol->case_element_list->accept(*this);
+	if (NULL != symbol->statement_list)
+		symbol->statement_list->accept(*this);
+	return NULL;
+}
+
+/********************************/
+/* B 3.2.4 Iteration Statements */
+/********************************/
+
+void *print_datatypes_error_c::visit(for_statement_c *symbol) {
+	symbol->control_variable->accept(*this);
+	symbol->beg_expression->accept(*this);
+	symbol->end_expression->accept(*this);
+	/* Control variable */
+	if ((NULL == symbol->control_variable->datatype) &&
+		(symbol->control_variable->candidate_datatypes.size() > 0)) {
+		STAGE3_ERROR(0, symbol, symbol, "Invalid data type for 'FOR' control variable.");
+	}
+	/* BEG expression */
+	if ((NULL == symbol->beg_expression->datatype) &&
+		(symbol->beg_expression->candidate_datatypes.size() > 0)) {
+		STAGE3_ERROR(0, symbol, symbol, "Invalid data type for 'FOR' begin expression.");
+	}
+	/* END expression */
+	if ((NULL == symbol->end_expression->datatype) &&
+		(symbol->end_expression->candidate_datatypes.size() > 0)) {
+		STAGE3_ERROR(0, symbol, symbol, "Invalid data type for 'FOR' end expression.");
+	}
+	/* BY expression */
+	if ((NULL != symbol->by_expression) &&
+		(NULL == symbol->by_expression->datatype) &&
+		(symbol->end_expression->candidate_datatypes.size() > 0)) {
+		STAGE3_ERROR(0, symbol, symbol, "Invalid data type for 'FOR' by expression.");
+	}
+	/* DO statement */
+	if (NULL != symbol->statement_list)
+		symbol->statement_list->accept(*this);
+
+	return NULL;
+}
+
+void *print_datatypes_error_c::visit(while_statement_c *symbol) {
+	symbol->expression->accept(*this);
+	if (!is_type_valid(symbol->expression->datatype)) {
+		STAGE3_ERROR(0, symbol, symbol, "Invalid data type for 'WHILE' condition.");
+		return NULL;
+	}
+	if (NULL != symbol->statement_list)
+		symbol->statement_list->accept(*this);
+	return NULL;
+}
+
+void *print_datatypes_error_c::visit(repeat_statement_c *symbol) {
+	if (!is_type_valid(symbol->expression->datatype)) {
+		STAGE3_ERROR(0, symbol, symbol, "Invalid data type for 'REPEAT' condition.");
+		return NULL;
+	}
+	if (NULL != symbol->statement_list)
+		symbol->statement_list->accept(*this);
+	symbol->expression->accept(*this);
+	return NULL;
+}
+
+
+
+
+