--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/stage3/lvalue_check.cc Wed Aug 22 16:46:17 2012 +0200
@@ -0,0 +1,559 @@
+/*
+ * matiec - a compiler for the programming languages defined in IEC 61131-3
+ *
+ * Copyright (C) 2009-2012 Mario de Sousa (msousa@fe.up.pt)
+ * Copyright (C) 2012 Manuele Conti (conti.ma@alice.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)
+ *
+ */
+
+
+
+/* Expressions on the left hand side of assignment statements have aditional restrictions on their datatype.
+ * For example, they cannot be literals, CONSTANT type variables, function invocations, etc...
+ * This class wil do those checks.
+ *
+ * Note that assignment may also be done when passing variables to OUTPUT or IN_OUT function parameters,so we check those too.
+ */
+
+
+
+#include "lvalue_check.hh"
+
+#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"); \
+ 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; \
+}
+
+
+lvalue_check_c::lvalue_check_c(symbol_c *ignore) {
+ error_count = 0;
+ current_display_error_level = 0;
+ current_il_operand = NULL;
+}
+
+lvalue_check_c::~lvalue_check_c(void) {
+}
+
+int lvalue_check_c::get_error_count() {
+ return error_count;
+}
+
+
+#include <strings.h>
+/* No writing to iterator variables (used in FOR loops) inside the loop itself */
+void lvalue_check_c::check_assignment_to_controlvar(symbol_c *lvalue) {
+ for (unsigned int i = 0; i < control_variables.size(); i++) {
+ token_c *lvalue_name = get_var_name_c::get_name(lvalue);
+ if (compare_identifiers(lvalue_name, control_variables[i]) == 0) {
+ STAGE3_ERROR(0, lvalue, lvalue, "Assignment to FOR control variable is not allowed.");
+ break;
+ }
+ }
+}
+
+
+/* fb_instance.var := ... is not valid if var is output variable */
+/* NOTE, if a fb_instance1.fb_instance2.fb_instance3.var is used, we must iteratively check that none of the
+ * FB records are declared as OUTPUT variables!!
+ * This is the reason why we have the while() loop in this function!
+ *
+ * Note, however, that the first record (fb_instance1 in the above example) may be an output variable!
+ */
+void lvalue_check_c::check_assignment_to_output(symbol_c *lvalue) {
+ decompose_var_instance_name_c decompose_lvalue(lvalue);
+ search_base_type_c search_base_type;
+
+ /* Get the first element/record of the potentially structured variable symbol */
+ /* Note that if symbol is pointing to an expression (or simply a literal value), it will return a NULL.
+ * Once we have implemented the check_assignment_to_expression() method, and abort calling the other checks (including this one)
+ * when an expression is found, we may replace this check with an assertion...
+ * if (NULL == struct_elem) ERROR;
+ */
+ symbol_c *struct_elem = decompose_lvalue.next_part();
+ if (NULL == struct_elem) return;
+
+ symbol_c *type_decl = search_var_instance_decl->get_decl(struct_elem);
+ // symbol_c *type_id = spec_init_sperator_c::get_spec(type_decl); /* this is not required! search_base_type_c can handle spec_init symbols! */
+ symbol_c *basetype_id = search_base_type.get_basetype_id(/*type_id*/ type_decl);
+ /* If we can not determine the data type of the element, then the code must have a data type semantic error.
+ * This will have been caught by the data type semantic verifier, so we do not bother with this anymore!
+ */
+ if (NULL == basetype_id) return;
+
+ /* Determine if the record/structure element is of a FB type. */
+ /* NOTE: If the structure element is not a FB type, then we can quit this check.
+ * Remember that the standard does not allow a STRUCT data type to have elements that are FB instances!
+ * Similarly, arrays of FB instances is also not allowed.
+ * So, as soon as we find one record/structure element that is not a FB, no other record/structure element
+ * will be of FB type, which means we can quit this check!
+ */
+ function_block_declaration_c *fb_decl = function_block_type_symtable.find_value(basetype_id);
+ if (function_block_type_symtable.end_value() == fb_decl) return;
+
+ while (NULL != (struct_elem = decompose_lvalue.next_part())) {
+ search_var_instance_decl_c fb_search_var_instance_decl(fb_decl);
+ if (search_var_instance_decl_c::output_vt == fb_search_var_instance_decl.get_vartype(struct_elem)) {
+ STAGE3_ERROR(0, struct_elem, struct_elem, "Assignment to FB output variable is not allowed.");
+ return; /* no need to carry on checking once the first error is found! */
+ }
+
+ /* prepare for any possible further record/structure elements */
+ type_decl = fb_search_var_instance_decl.get_decl(struct_elem);
+ basetype_id = search_base_type.get_basetype_id(type_decl);
+ if (NULL == basetype_id) return; /* same comment as above... */
+ fb_decl = function_block_type_symtable.find_value(basetype_id);
+ if (function_block_type_symtable.end_value() == fb_decl) return; /* same comment as above... */
+ }
+}
+
+
+/* No writing to CONSTANTs */
+void lvalue_check_c::check_assignment_to_constant(symbol_c *lvalue) {
+ unsigned int option = search_var_instance_decl->get_option(lvalue);
+ if (option == search_var_instance_decl_c::constant_opt) {
+ STAGE3_ERROR(0, lvalue, lvalue, "Assignment to CONSTANT variables is not be allowed.");
+ }
+}
+
+
+/* No assigning values to expressions. */
+void lvalue_check_c::check_assignment_to_expression(symbol_c *lvalue) {
+ /* This may occur in function invocations, when passing values (possibly an expression) to one
+ * of the function's OUTPUT or IN_OUT parameters.
+ */
+ /* This may occur in function invocations, when passing values (possibly an expression) to one
+ * of the function's OUTPUT or IN_OUT parameters.
+ */
+ if (
+ /*********************/
+ /* B 1.2 - Constants */
+ /*********************/
+ /******************************/
+ /* B 1.2.1 - Numeric Literals */
+ /******************************/
+ (typeid( *lvalue ) == typeid( real_c )) ||
+ (typeid( *lvalue ) == typeid( integer_c )) ||
+ (typeid( *lvalue ) == typeid( binary_integer_c )) ||
+ (typeid( *lvalue ) == typeid( octal_integer_c )) ||
+ (typeid( *lvalue ) == typeid( hex_integer_c )) ||
+ (typeid( *lvalue ) == typeid( neg_real_c )) ||
+ (typeid( *lvalue ) == typeid( neg_integer_c )) ||
+ (typeid( *lvalue ) == typeid( integer_literal_c )) ||
+ (typeid( *lvalue ) == typeid( real_literal_c )) ||
+ (typeid( *lvalue ) == typeid( bit_string_literal_c )) ||
+ (typeid( *lvalue ) == typeid( boolean_literal_c )) ||
+ (typeid( *lvalue ) == typeid( boolean_true_c )) || /* should not really be needed */
+ (typeid( *lvalue ) == typeid( boolean_false_c )) || /* should not really be needed */
+ /*******************************/
+ /* B.1.2.2 Character Strings */
+ /*******************************/
+ (typeid( *lvalue ) == typeid( double_byte_character_string_c )) ||
+ (typeid( *lvalue ) == typeid( single_byte_character_string_c )) ||
+ /***************************/
+ /* B 1.2.3 - Time Literals */
+ /***************************/
+ /************************/
+ /* B 1.2.3.1 - Duration */
+ /************************/
+ (typeid( *lvalue ) == typeid( duration_c )) ||
+ /************************************/
+ /* B 1.2.3.2 - Time of day and Date */
+ /************************************/
+ (typeid( *lvalue ) == typeid( time_of_day_c )) ||
+ (typeid( *lvalue ) == typeid( daytime_c )) || /* should not really be needed */
+ (typeid( *lvalue ) == typeid( date_c )) || /* should not really be needed */
+ (typeid( *lvalue ) == typeid( date_literal_c )) ||
+ (typeid( *lvalue ) == typeid( date_and_time_c )) ||
+ /***************************************/
+ /* B.3 - Language ST (Structured Text) */
+ /***************************************/
+ /***********************/
+ /* B 3.1 - Expressions */
+ /***********************/
+ (typeid( *lvalue ) == typeid( or_expression_c )) ||
+ (typeid( *lvalue ) == typeid( xor_expression_c )) ||
+ (typeid( *lvalue ) == typeid( and_expression_c )) ||
+ (typeid( *lvalue ) == typeid( equ_expression_c )) ||
+ (typeid( *lvalue ) == typeid( notequ_expression_c )) ||
+ (typeid( *lvalue ) == typeid( lt_expression_c )) ||
+ (typeid( *lvalue ) == typeid( gt_expression_c )) ||
+ (typeid( *lvalue ) == typeid( le_expression_c )) ||
+ (typeid( *lvalue ) == typeid( ge_expression_c )) ||
+ (typeid( *lvalue ) == typeid( add_expression_c )) ||
+ (typeid( *lvalue ) == typeid( sub_expression_c )) ||
+ (typeid( *lvalue ) == typeid( mul_expression_c )) ||
+ (typeid( *lvalue ) == typeid( div_expression_c )) ||
+ (typeid( *lvalue ) == typeid( mod_expression_c )) ||
+ (typeid( *lvalue ) == typeid( power_expression_c )) ||
+ (typeid( *lvalue ) == typeid( neg_expression_c )) ||
+ (typeid( *lvalue ) == typeid( not_expression_c )) ||
+ (typeid( *lvalue ) == typeid( function_invocation_c )))
+ STAGE3_ERROR(0, lvalue, lvalue, "Assigning an expression to an OUT or IN_OUT parameter is not allowed.");
+}
+
+
+
+
+
+
+
+void lvalue_check_c::verify_is_lvalue(symbol_c *lvalue) {
+ int init_error_count = error_count; /* stop the checks once an error has been found... */
+ if (error_count == init_error_count) check_assignment_to_expression(lvalue);
+ if (error_count == init_error_count) check_assignment_to_controlvar(lvalue);
+ if (error_count == init_error_count) check_assignment_to_output(lvalue);
+ if (error_count == init_error_count) check_assignment_to_constant(lvalue);
+}
+
+
+
+
+/* check whether all values passed to OUT or IN_OUT parameters are legal lvalues. */
+/*
+ * All parameters being passed to the called function MUST be in the parameter list to which f_call points to!
+ * This means that, for non formal function calls in IL, de current (default value) must be artificially added to the
+ * beginning of the parameter list BEFORE calling handle_function_call().
+ */
+#include <string.h> /* required for strcmp() */
+void lvalue_check_c::check_nonformal_call(symbol_c *f_call, symbol_c *f_decl) {
+ symbol_c *call_param_value;
+ identifier_c *param_name;
+ function_param_iterator_c fp_iterator(f_decl);
+ function_call_param_iterator_c fcp_iterator(f_call);
+
+ /* Iterating through the non-formal parameters of the function call */
+ while((call_param_value = fcp_iterator.next_nf()) != NULL) {
+ /* Iterate to the next parameter of the function being called.
+ * Get the name of that parameter, and ignore if EN or ENO.
+ */
+ do {
+ param_name = fp_iterator.next();
+ /* If there is no other parameter declared, then we are passing too many parameters... */
+ /* This error should have been caught in data type verification, so we simply abandon our check! */
+ if(param_name == NULL) return;
+ } while ((strcmp(param_name->value, "EN") == 0) || (strcmp(param_name->value, "ENO") == 0));
+
+ /* Determine the direction (IN, OUT, IN_OUT) of the parameter... */
+ function_param_iterator_c::param_direction_t param_direction = fp_iterator.param_direction();
+
+ /* We only process the parameter value if the paramater itself is valid... */
+ if (param_name != NULL) {
+ /* If the parameter is either OUT or IN_OUT, we check if 'call_param_value' is a valid lvalue */
+ if ((function_param_iterator_c::direction_out == param_direction) || (function_param_iterator_c::direction_inout == param_direction))
+ verify_is_lvalue(call_param_value);
+ /* parameter values to IN parameters may be expressions with function invocations that must also be checked! */
+ if (function_param_iterator_c::direction_in == param_direction)
+ call_param_value->accept(*this);
+ }
+ }
+}
+
+
+
+
+
+
+/* check whether all values passed to OUT or IN_OUT parameters are legal lvalues. */
+void lvalue_check_c::check_formal_call(symbol_c *f_call, symbol_c *f_decl) {
+ /* if data type semantic verification was unable to determine which function is being called,
+ * then it does not make sense to go ahead and check for lvalues to unknown parameters.
+ * We simply bug out!
+ */
+ if (NULL == f_decl) return;
+
+ symbol_c *call_param_name;
+ function_param_iterator_c fp_iterator(f_decl);
+ function_call_param_iterator_c fcp_iterator(f_call);
+
+ /* Iterating through the formal parameters of the function call */
+ while((call_param_name = fcp_iterator.next_f()) != NULL) {
+
+ /* Obtaining the value being passed in the function call */
+ symbol_c *call_param_value = fcp_iterator.get_current_value();
+ if (NULL == call_param_value) ERROR;
+
+ /* Find the corresponding parameter in function declaration, and it's direction (IN, OUT, IN_OUT) */
+ identifier_c *param_name = fp_iterator.search(call_param_name);
+ function_param_iterator_c::param_direction_t param_direction = fp_iterator.param_direction();
+
+ /* We only process the parameter value if the paramater itself is valid... */
+ if (param_name != NULL) {
+ /* If the parameter is either OUT or IN_OUT, we check if 'call_param_value' is a valid lvalue */
+ if ((function_param_iterator_c::direction_out == param_direction) || (function_param_iterator_c::direction_inout == param_direction))
+ verify_is_lvalue(call_param_value);
+ /* parameter values to IN parameters may be expressions with function invocations that must also be checked! */
+ if (function_param_iterator_c::direction_in == param_direction)
+ call_param_value->accept(*this);
+
+ }
+ }
+}
+
+
+
+
+
+
+
+/**************************************/
+/* B 1.5 - Program organisation units */
+/**************************************/
+/***********************/
+/* B 1.5.1 - Functions */
+/***********************/
+void *lvalue_check_c::visit(function_declaration_c *symbol) {
+ search_varfb_instance_type = new search_varfb_instance_type_c(symbol);
+ search_var_instance_decl = new search_var_instance_decl_c(symbol);
+ symbol->function_body->accept(*this);
+ delete search_varfb_instance_type;
+ delete search_var_instance_decl;
+ search_varfb_instance_type = NULL;
+ search_var_instance_decl = NULL;
+ return NULL;
+}
+
+/*****************************/
+/* B 1.5.2 - Function blocks */
+/*****************************/
+void *lvalue_check_c::visit(function_block_declaration_c *symbol) {
+ search_varfb_instance_type = new search_varfb_instance_type_c(symbol);
+ search_var_instance_decl = new search_var_instance_decl_c(symbol);
+ symbol->fblock_body->accept(*this);
+ delete search_varfb_instance_type;
+ delete search_var_instance_decl;
+ search_varfb_instance_type = NULL;
+ search_var_instance_decl = NULL;
+ return NULL;
+}
+
+/**********************/
+/* B 1.5.3 - Programs */
+/**********************/
+void *lvalue_check_c::visit(program_declaration_c *symbol) {
+ search_varfb_instance_type = new search_varfb_instance_type_c(symbol);
+ search_var_instance_decl = new search_var_instance_decl_c(symbol);
+ symbol->function_block_body->accept(*this);
+ delete search_varfb_instance_type;
+ delete search_var_instance_decl;
+ search_varfb_instance_type = NULL;
+ search_var_instance_decl = NULL;
+ return NULL;
+}
+
+/****************************************/
+/* B.2 - Language IL (Instruction List) */
+/****************************************/
+/***********************************/
+/* B 2.1 Instructions and Operands */
+/***********************************/
+void *lvalue_check_c::visit(il_instruction_c *symbol) {
+ /* il_instruction will be NULL when parsing a label with no instruction
+ * e.g.: label1: <---- il_instruction = NULL!
+ * LD 33
+ * ...
+ */
+ if (NULL != symbol->il_instruction)
+ symbol->il_instruction->accept(*this);
+ return NULL;
+}
+
+void *lvalue_check_c::visit(il_simple_operation_c *symbol) {
+ current_il_operand = symbol->il_operand;
+ symbol->il_simple_operator->accept(*this);
+ current_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 *lvalue_check_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 at the end of this method.
+ */
+ /* TODO: Copying the location data will result in confusing error message.
+ * We need to make this better, by inserting code to handle this special situation explicitly!
+ */
+ /* NOTE: When calling a function, using the 'current value' as the first parameter of the function invocation
+ * implies that we can only call functions whose first parameter is IN. It would not do to pass
+ * the 'current value' to an OUT or IN_OUT parameter.
+ * In order to make sure that this will be caught by the check_nonformal_call() function,
+ * we add a symbol that cannot be an lvalue; in this case, a real_c (REAL literal).
+ */
+ real_c param_value(NULL);
+ *((symbol_c *)(¶m_value)) = *((symbol_c *)symbol); /* copy the symbol location (file, line, offset) data */
+ 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(¶m_value, 0);
+
+ check_nonformal_call(symbol, symbol->called_function_declaration);
+
+ /* Undo the changes to the abstract syntax tree we 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_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 *lvalue_check_c::visit(il_fb_call_c *symbol) {
+ if (NULL != symbol->il_operand_list) check_nonformal_call(symbol, symbol->called_fb_declaration);
+ if (NULL != symbol-> il_param_list) check_formal_call(symbol, symbol->called_fb_declaration);
+ 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 *lvalue_check_c::visit(il_formal_funct_call_c *symbol) {
+ check_formal_call(symbol, symbol->called_function_declaration);
+ return NULL;
+}
+
+
+
+
+
+
+/*******************/
+/* B 2.2 Operators */
+/*******************/
+void *lvalue_check_c::visit(ST_operator_c *symbol) {
+ verify_is_lvalue(current_il_operand);
+ return NULL;
+}
+
+void *lvalue_check_c::visit(STN_operator_c *symbol) {
+ verify_is_lvalue(current_il_operand);
+ return NULL;
+}
+
+void *lvalue_check_c::visit(S_operator_c *symbol) {
+ verify_is_lvalue(current_il_operand);
+ return NULL;
+}
+
+void *lvalue_check_c::visit(R_operator_c *symbol) {
+ verify_is_lvalue(current_il_operand);
+ return NULL;
+}
+
+
+/***************************************/
+/* B.3 - Language ST (Structured Text) */
+/***************************************/
+/***********************/
+/* B 3.1 - Expressions */
+/***********************/
+// 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 *lvalue_check_c::visit(function_invocation_c *symbol) {
+ if (NULL != symbol->formal_param_list ) check_formal_call (symbol, symbol->called_function_declaration);
+ if (NULL != symbol->nonformal_param_list) check_nonformal_call(symbol, symbol->called_function_declaration);
+ return NULL;
+}
+
+/*********************************/
+/* B 3.2.1 Assignment Statements */
+/*********************************/
+void *lvalue_check_c::visit(assignment_statement_c *symbol) {
+ verify_is_lvalue(symbol->l_exp);
+ /* We call visit r_exp to check function_call */
+ symbol->r_exp->accept(*this);
+ return NULL;
+}
+
+/*****************************************/
+/* B 3.2.2 Subprogram Control Statements */
+/*****************************************/
+void *lvalue_check_c::visit(fb_invocation_c *symbol) {
+ if (NULL != symbol->formal_param_list ) check_formal_call (symbol, symbol->called_fb_declaration);
+ if (NULL != symbol->nonformal_param_list) check_nonformal_call(symbol, symbol->called_fb_declaration);
+ return NULL;
+}
+
+/********************************/
+/* B 3.2.4 Iteration Statements */
+/********************************/
+void *lvalue_check_c::visit(for_statement_c *symbol) {
+ verify_is_lvalue(symbol->control_variable);
+ control_variables.push_back(get_var_name_c::get_name(symbol->control_variable));
+ symbol->statement_list->accept(*this);
+ control_variables.pop_back();
+ return NULL;
+}
+
+
+
+
+
+
+