matiec: comparison stage4/generate_c/generate_c

equal deleted inserted replaced

-:be4373d07201
+:0f7bcc160568
 */
 if (   get_datatype_info_c::is_function_block(symbol->record_variable->datatype)
 || get_datatype_info_c::is_sfc_step      (symbol->record_variable->datatype)) {
 if (NULL == symbol->record_variable->scope) ERROR;
 search_var_instance_decl_c search_var_instance_decl(symbol->record_variable->scope);
-if (search_var_instance_decl_c::external_vt == search_var_instance_decl.get_vartype(get_var_name_c::get_last_field(symbol->record_variable)))
+if      (search_var_instance_decl_c::external_vt == search_var_instance_decl.get_vartype(get_var_name_c::get_last_field(symbol->record_variable)))
-s4o.print("->");
+s4o.print("->"); /* please read the comment in visit(deref_operator_c *) tio understand what this line is doing! */
+else if (dynamic_cast<deref_operator_c *>(symbol->record_variable) != NULL)
+s4o.print("->"); /* please read the comment in visit(deref_operator_c *) tio understand what this line is doing! */
 else
 s4o.print(".");
 symbol->field_selector->accept(*this);
 }
 break;
 case complextype_suffix_vg:
 symbol->record_variable->accept(*this);
 // the following condition MUST be a negation of the above condition used in the 'case complextype_base_vg:'
 if (!(   get_datatype_info_c::is_function_block(symbol->record_variable->datatype)     // if the record variable is not a FB...
 || get_datatype_info_c::is_sfc_step      (symbol->record_variable->datatype))) { // ...nor an SFC step name, then it will certainly be a structure!
-s4o.print(".");
+if (dynamic_cast<deref_operator_c *>(symbol->record_variable) != NULL)
+s4o.print("->"); /* please read the comment in visit(deref_operator_c *) tio understand what this line is doing! */
+else
+s4o.print(".");
 symbol->field_selector->accept(*this);
 }
 break;
 default:
 if (this->is_variable_prefix_null()) {
+/* We are writing code for a FUNCTION. In this case, deref_operator_c are not transformed into the C pointer derefence syntax '->' (e.g. ptr->elem).
+* We use instead the '*' syntax (e.g. (*ptr).elem)
+* While in FB the '->' is generated by this structured_variable_c visitor, in Functions the '*' syntax is generated by the deref_operator_c visitor
+* This is why here we do NOT have --> {if (dynamic_cast<deref_operator_c *>(symbol->record_variable) != NULL)  ..}
+	 *
+	 * please read the comment in visit(deref_operator_c *) for more information!
+*/
 symbol->record_variable->accept(*this);
 s4o.print(".");
 symbol->field_selector->accept(*this);
 }
 else
 /* B.3 - Language ST (Structured Text) */
 /***************************************/
 /***********************/
 /* B 3.1 - Expressions */
 /***********************/
+void *visit(deref_operator_c *symbol) {
+/* When producing C code for FUNCTION_BLOCKS, we use the '*' syntax (e.g. (*ptr).elem)
+* When producing C code for a FUNCTION_BLOCK, the deref_operator_c are transformed in two ways, depending on where they occur.
+*    - deref_operator between a struct and its elem (e.g. struct_ref^.elem1)
+*        are transformed into C using the C pointer derefence syntax '->' (e.g. struct_ref->elem1).
+*        (In this case, '->' is generated by this structured_variable_c visitor)
+*    - deref_operator at the end of a struct variable (e.g. struct.elem_ptr^)
+*        are transformed using the '*' syntax for C pointer dereferencing (e.g. *(struct.elem_ptr) )
+*
+*   NOTE: Ideally, we should always use the '*' C pointer dereferencing syntax. However, due to the
+*         was the GET_VAR and SET_VAR are transformed into C, this does not work for '^' between a struct and its
+*         element (e.g. struct_ref^.elem), which is whey in this case only we use the '->' syntax.
+*   NOTE: The use of the -> syntax means that pointers to pointers are not supported betweem a struct and its elem
+*         (e.g. . struct_ref_ref^^.elem) as this would be transformed into the invalid C code struct_ref_ref->->elem.
+*         This is why we add a test for this case, and bug out with an error if we encounter it!!
+*/
+if (this->is_variable_prefix_null()) {
+/* For code in FUNCTIONs */
+s4o.print("(*");
+symbol->exp->accept(*this);
+s4o.print(")");
+} else {
+/* For code in FBs, and PROGRAMS... */
+if (NULL == dynamic_cast<structured_variable_c *>(symbol->parent)) {
+s4o.print("(*");
+symbol->exp->accept(*this);
+s4o.print(")");
+} else {
+/* We are in a structured variable - the structured_variable_c itself will already have printed out the '->' !! */
+if (NULL != dynamic_cast<deref_operator_c *>(symbol->exp))
+STAGE4_ERROR(symbol, symbol->exp, "The use of consecutive derefencing operators between a struct and its elem (ex: struct_ref_ref^^.elem) is currently not supported for code inside a Function_Block.");
+symbol->exp->accept(*this);
+}
+}
+return NULL;
+}
 void *visit(deref_expression_c *symbol) {
 s4o.print("(");
 if (this->is_variable_prefix_null()) {
 /* For code in FUNCTIONs */
 s4o.print("*");
 symbol->exp->accept(*this);
 s4o.print("");
 } else {
 /* For code in FBs, and PROGRAMS... */
-s4o.print("(");
 unsigned int vartype = analyse_variable_c::first_nonfb_vardecltype(symbol->exp, scope_);
 if (vartype == search_var_instance_decl_c::external_vt) {
 if (!get_datatype_info_c::is_type_valid    (symbol->exp->datatype)) ERROR;
 if ( get_datatype_info_c::is_function_block(symbol->exp->datatype))
 s4o.print(GET_EXTERNAL_FB_DREF);
 s4o.print(",");
 wanted_variablegeneration = complextype_suffix_vg;
 symbol->exp->accept(*this);
 s4o.print(")");
 wanted_variablegeneration = old_wanted_variablegeneration;
-s4o.print(")");
 }
 s4o.print(")");
 return NULL;
 }

changeset 936	0f7bcc160568
parent 933	76324f461aed
child 941	c2ef93412407