Use semantic_assign() properly.
[cparser] / parser.c
index 628ac66..a42e169 100644 (file)
--- a/parser.c
+++ b/parser.c
@@ -50,6 +50,8 @@ static declaration_t      *last_declaration  = NULL;
 static declaration_t      *current_function  = NULL;
 static switch_statement_t *current_switch    = NULL;
 static statement_t        *current_loop      = NULL;
+static goto_statement_t   *goto_first        = NULL;
+static goto_statement_t   *goto_last         = NULL;
 static struct obstack  temp_obst;
 
 /** The current source position. */
@@ -134,6 +136,13 @@ static void *allocate_ast_zero(size_t size)
        return res;
 }
 
+static declaration_t *allocate_declaration_zero(void)
+{
+       declaration_t *declaration = allocate_ast_zero(sizeof(*allocate_declaration_zero()));
+       declaration->type = type_error_type;
+       return declaration;
+}
+
 /**
  * Returns the size of a statement node.
  *
@@ -227,7 +236,8 @@ static expression_t *allocate_expression_zero(expression_kind_t kind)
        size_t        size = get_expression_struct_size(kind);
        expression_t *res  = allocate_ast_zero(size);
 
-       res->base.kind = kind;
+       res->base.kind     = kind;
+       res->base.datatype = type_error_type;
        return res;
 }
 
@@ -461,14 +471,6 @@ static void eat_paren(void)
     }                                              \
     next_token();
 
-#define expect_fail(expected)                      \
-    if(UNLIKELY(token.type != (expected))) {       \
-        parse_error_expected(NULL, (expected), 0); \
-        eat_statement();                           \
-        goto fail;                                 \
-    }                                              \
-    next_token();
-
 #define expect_block(expected)                     \
     if(UNLIKELY(token.type != (expected))) {       \
         parse_error_expected(NULL, (expected), 0); \
@@ -765,29 +767,34 @@ static expression_t *create_implicit_cast(expression_t *expression,
                                        expression->base.source_position, source_type, dest_type);
                        return expression;
 
+               case TYPE_COMPOUND_STRUCT:
+               case TYPE_COMPOUND_UNION:
+               case TYPE_ERROR:
+                       return expression;
+
                default:
                        panic("casting of non-atomic types not implemented yet");
        }
 }
 
 /** Implements the rules from ยง 6.5.16.1 */
-static void semantic_assign(type_t *orig_type_left, expression_t **right,
+static type_t *semantic_assign(type_t *orig_type_left,
+                            const expression_t *const right,
                             const char *context)
 {
-       type_t *orig_type_right = (*right)->base.datatype;
+       type_t *const orig_type_right = right->base.datatype;
 
-       if(orig_type_right == NULL)
-               return;
+       if (!is_type_valid(orig_type_right))
+               return orig_type_right;
 
        type_t *const type_left  = skip_typeref(orig_type_left);
        type_t *const type_right = skip_typeref(orig_type_right);
 
        if ((is_type_arithmetic(type_left) && is_type_arithmetic(type_right)) ||
-           (is_type_pointer(type_left) && is_null_pointer_constant(*right)) ||
+           (is_type_pointer(type_left) && is_null_pointer_constant(right)) ||
            (is_type_atomic(type_left, ATOMIC_TYPE_BOOL)
                && is_type_pointer(type_right))) {
-               *right = create_implicit_cast(*right, type_left);
-               return;
+               return orig_type_left;
        }
 
        if (is_type_pointer(type_left) && is_type_pointer(type_right)) {
@@ -804,7 +811,7 @@ static void semantic_assign(type_t *orig_type_left, expression_t **right,
                        = points_to_right->base.qualifiers & ~points_to_left->base.qualifiers;
                if(missing_qualifiers != 0) {
                        errorf(HERE, "destination type '%T' in %s from type '%T' lacks qualifiers '%Q' in pointed-to type", type_left, context, type_right, missing_qualifiers);
-                       return;
+                       return orig_type_left;
                }
 
                points_to_left  = get_unqualified_type(points_to_left);
@@ -813,23 +820,21 @@ static void semantic_assign(type_t *orig_type_left, expression_t **right,
                if(!is_type_atomic(points_to_left, ATOMIC_TYPE_VOID)
                                && !is_type_atomic(points_to_right, ATOMIC_TYPE_VOID)
                                && !types_compatible(points_to_left, points_to_right)) {
-                       goto incompatible_assign_types;
+                       return NULL;
                }
 
-               *right = create_implicit_cast(*right, type_left);
-               return;
+               return orig_type_left;
        }
 
-       if (is_type_compound(type_left)
-                       && types_compatible(type_left, type_right)) {
-               *right = create_implicit_cast(*right, type_left);
-               return;
+       if (is_type_compound(type_left)  && is_type_compound(type_right)) {
+               type_t *const unqual_type_left  = get_unqualified_type(type_left);
+               type_t *const unqual_type_right = get_unqualified_type(type_right);
+               if (types_compatible(unqual_type_left, unqual_type_right)) {
+                       return orig_type_left;
+               }
        }
 
-incompatible_assign_types:
-       /* TODO: improve error message */
-       errorf(HERE, "incompatible types in %s", context);
-       errorf(HERE, "'%T' <- '%T'", orig_type_left, orig_type_right);
+       return NULL;
 }
 
 static expression_t *parse_constant_expression(void)
@@ -854,7 +859,7 @@ static type_t *make_global_typedef(const char *name, type_t *type)
 {
        symbol_t *const symbol       = symbol_table_insert(name);
 
-       declaration_t *declaration   = allocate_ast_zero(sizeof(declaration[0]));
+       declaration_t *const declaration = allocate_declaration_zero();
        declaration->namespc         = NAMESPACE_NORMAL;
        declaration->storage_class   = STORAGE_CLASS_TYPEDEF;
        declaration->type            = type;
@@ -869,15 +874,15 @@ static type_t *make_global_typedef(const char *name, type_t *type)
        return typedef_type;
 }
 
-static const char *parse_string_literals(void)
+static string_t parse_string_literals(void)
 {
        assert(token.type == T_STRING_LITERAL);
-       const char *result = token.v.string;
+       string_t result = token.v.string;
 
        next_token();
 
-       while(token.type == T_STRING_LITERAL) {
-               result = concat_strings(result, token.v.string);
+       while (token.type == T_STRING_LITERAL) {
+               result = concat_strings(&result, &token.v.string);
                next_token();
        }
 
@@ -980,13 +985,13 @@ static designator_t *parse_designation(void)
 #endif
 
 static initializer_t *initializer_from_string(array_type_t *type,
-                                              const char *string)
+                                              const string_t *const string)
 {
        /* TODO: check len vs. size of array type */
        (void) type;
 
        initializer_t *initializer = allocate_initializer_zero(INITIALIZER_STRING);
-       initializer->string.string = string;
+       initializer->string.string = *string;
 
        return initializer;
 }
@@ -1020,7 +1025,7 @@ static initializer_t *initializer_from_expression(type_t *type,
                                case EXPR_STRING_LITERAL:
                                        if (element_type->atomic.akind == ATOMIC_TYPE_CHAR) {
                                                return initializer_from_string(array_type,
-                                                       expression->string.value);
+                                                       &expression->string.value);
                                        }
 
                                case EXPR_WIDE_STRING_LITERAL: {
@@ -1037,17 +1042,14 @@ static initializer_t *initializer_from_expression(type_t *type,
                }
        }
 
-       type_t *expression_type = skip_typeref(expression->base.datatype);
-       if(is_type_scalar(type) || types_compatible(type, expression_type)) {
-               semantic_assign(type, &expression, "initializer");
-
-               initializer_t *result = allocate_initializer_zero(INITIALIZER_VALUE);
-               result->value.value   = expression;
+       type_t *const res_type = semantic_assign(type, expression, "initializer");
+       if (res_type == NULL)
+               return NULL;
 
-               return result;
-       }
+       initializer_t *const result = allocate_initializer_zero(INITIALIZER_VALUE);
+       result->value.value = create_implicit_cast(expression, res_type);
 
-       return NULL;
+       return result;
 }
 
 static initializer_t *parse_sub_initializer(type_t *type,
@@ -1257,17 +1259,23 @@ static initializer_t *parse_sub_initializer(type_t *type,
        return result;
 }
 
-static initializer_t *parse_initializer(type_t *type)
+static initializer_t *parse_initializer(type_t *const orig_type)
 {
        initializer_t *result;
 
-       type = skip_typeref(type);
+       type_t *const type = skip_typeref(orig_type);
 
        if(token.type != '{') {
                expression_t  *expression  = parse_assignment_expression();
+               if (expression->base.datatype == NULL) {
+                       /* something bad happens, don't produce further errors */
+                       return NULL;
+               }
                initializer_t *initializer = initializer_from_expression(type, expression);
                if(initializer == NULL) {
-                       errorf(HERE, "initializer expression '%E', type '%T' is incompatible with type '%T'", expression, expression->base.datatype, type);
+                       errorf(HERE,
+                               "initializer expression '%E' of type '%T' is incompatible with type '%T'",
+                               expression, expression->base.datatype, orig_type);
                }
                return initializer;
        }
@@ -1331,13 +1339,9 @@ static declaration_t *parse_compound_type_specifier(bool is_struct)
        }
 
        if(declaration == NULL) {
-               declaration = allocate_ast_zero(sizeof(declaration[0]));
-
-               if(is_struct) {
-                       declaration->namespc = NAMESPACE_STRUCT;
-               } else {
-                       declaration->namespc = NAMESPACE_UNION;
-               }
+               declaration = allocate_declaration_zero();
+               declaration->namespc         =
+                       (is_struct ? NAMESPACE_STRUCT : NAMESPACE_UNION);
                declaration->source_position = token.source_position;
                declaration->symbol          = symbol;
                declaration->parent_context  = context;
@@ -1371,7 +1375,7 @@ static declaration_t *parse_compound_type_specifier(bool is_struct)
        return declaration;
 }
 
-static void parse_enum_entries(enum_type_t *const enum_type)
+static void parse_enum_entries(type_t *const enum_type)
 {
        eat('{');
 
@@ -1382,15 +1386,15 @@ static void parse_enum_entries(enum_type_t *const enum_type)
        }
 
        do {
-               declaration_t *entry = allocate_ast_zero(sizeof(entry[0]));
-
                if(token.type != T_IDENTIFIER) {
                        parse_error_expected("while parsing enum entry", T_IDENTIFIER, 0);
                        eat_block();
                        return;
                }
+
+               declaration_t *const entry = allocate_declaration_zero();
                entry->storage_class   = STORAGE_CLASS_ENUM_ENTRY;
-               entry->type            = (type_t*) enum_type;
+               entry->type            = enum_type;
                entry->symbol          = token.v.symbol;
                entry->source_position = token.source_position;
                next_token();
@@ -1434,9 +1438,8 @@ static type_t *parse_enum_specifier(void)
        }
 
        if(declaration == NULL) {
-               declaration = allocate_ast_zero(sizeof(declaration[0]));
-
-               declaration->namespc       = NAMESPACE_ENUM;
+               declaration = allocate_declaration_zero();
+               declaration->namespc         = NAMESPACE_ENUM;
                declaration->source_position = token.source_position;
                declaration->symbol          = symbol;
                declaration->parent_context  = context;
@@ -1455,7 +1458,7 @@ static type_t *parse_enum_specifier(void)
                append_declaration(declaration);
                declaration->init.is_defined = 1;
 
-               parse_enum_entries(&type->enumt);
+               parse_enum_entries(type);
                parse_attributes();
        }
 
@@ -1677,7 +1680,7 @@ static void parse_declaration_specifiers(declaration_specifiers_t *specifiers)
                        }
                        break;
 
-               /* TODO: if type != NULL for the following rules should issue
+               /* TODO: if is_type_valid(type) for the following rules should issue
                 * an error */
                case T_struct: {
                        type = allocate_type_zero(TYPE_COMPOUND_STRUCT);
@@ -1878,8 +1881,7 @@ static declaration_t *parse_identifier_list(void)
        declaration_t *declarations     = NULL;
        declaration_t *last_declaration = NULL;
        do {
-               declaration_t *declaration = allocate_ast_zero(sizeof(declaration[0]));
-
+               declaration_t *const declaration = allocate_declaration_zero();
                declaration->source_position = token.source_position;
                declaration->symbol          = token.v.symbol;
                next_token();
@@ -2275,14 +2277,14 @@ static type_t *construct_declarator_type(construct_type_t *construct_list,
 static declaration_t *parse_declarator(
                const declaration_specifiers_t *specifiers, bool may_be_abstract)
 {
-       type_t        *type         = specifiers->type;
-       declaration_t *declaration  = allocate_ast_zero(sizeof(declaration[0]));
+       declaration_t *const declaration = allocate_declaration_zero();
        declaration->storage_class  = specifiers->storage_class;
        declaration->modifiers      = specifiers->decl_modifiers;
        declaration->is_inline      = specifiers->is_inline;
 
        construct_type_t *construct_type
                = parse_inner_declarator(declaration, may_be_abstract);
+       type_t *const type = specifiers->type;
        declaration->type = construct_declarator_type(construct_type, type);
 
        if(construct_type != NULL) {
@@ -2376,7 +2378,7 @@ warn_redundant_declaration:
                                        errorf(declaration->source_position, "static declaration of '%Y' follows non-static declaration", symbol);
                                        errorf(previous_declaration->source_position, "previous declaration of '%Y' was here", symbol);
                                } else {
-                                       if (old_storage_class != STORAGE_CLASS_EXTERN) {
+                                       if (old_storage_class != STORAGE_CLASS_EXTERN && !is_function_definition) {
                                                goto warn_redundant_declaration;
                                        }
                                        if (new_storage_class == STORAGE_CLASS_NONE) {
@@ -2405,9 +2407,54 @@ warn_redundant_declaration:
        return append_declaration(declaration);
 }
 
+/**
+ * Check if a given type is a vilid array type.
+ */
+static bool is_valid_array_type(const type_t *type) {
+       if (type->kind == TYPE_ARRAY) {
+               const array_type_t *array = &type->array;
+               const type_t       *etype = skip_typeref(array->element_type);
+
+               if (! is_valid_array_type(etype))
+                       return false;
+
+               if (etype->kind == TYPE_ATOMIC) {
+                       const atomic_type_t *atype = &etype->atomic;
+
+                       if (atype->akind == ATOMIC_TYPE_VOID) {
+                               return false;
+                       }
+               }
+       }
+       return true;
+}
+
 static declaration_t *record_declaration(declaration_t *declaration)
 {
-       return internal_record_declaration(declaration, false);
+       declaration = internal_record_declaration(declaration, false);
+       const type_t *type = skip_typeref(declaration->type);
+
+       /* check the type here for several not allowed combinations */
+       if (type->kind == TYPE_FUNCTION) {
+               const function_type_t* function_type = &type->function;
+               const type_t*          ret_type      = skip_typeref(function_type->return_type);
+
+               if (ret_type->kind == TYPE_FUNCTION) {
+                       errorf(declaration->source_position, "'%Y' declared as function returning a function",
+                               declaration->symbol);
+                       declaration->type = type_error_type;
+               } else if (ret_type->kind == TYPE_ARRAY) {
+                       errorf(declaration->source_position, "'%Y' declared as function returning an array",
+                               declaration->symbol);
+                       declaration->type = type_error_type;
+               }
+       }
+       if (! is_valid_array_type(type)) {
+               errorf(declaration->source_position, "declaration of '%Y' as array of voids",
+                               declaration->symbol);
+               declaration->type = type_error_type;
+       }
+       return declaration;
 }
 
 static declaration_t *record_function_definition(declaration_t *const declaration)
@@ -2448,9 +2495,7 @@ static void parse_init_declarator_rest(declaration_t *declaration)
        eat('=');
 
        type_t *orig_type = declaration->type;
-       type_t *type      = NULL;
-       if(orig_type != NULL)
-               type = skip_typeref(orig_type);
+       type_t *type      = type = skip_typeref(orig_type);
 
        if(declaration->init.initializer != NULL) {
                parser_error_multiple_definition(declaration, token.source_position);
@@ -2460,7 +2505,7 @@ static void parse_init_declarator_rest(declaration_t *declaration)
 
        /* ยง 6.7.5 (22)  array initializers for arrays with unknown size determine
         * the array type size */
-       if(type != NULL && is_type_array(type) && initializer != NULL) {
+       if(is_type_array(type) && initializer != NULL) {
                array_type_t *array_type = &type->array;
 
                if(array_type->size == NULL) {
@@ -2477,7 +2522,7 @@ static void parse_init_declarator_rest(declaration_t *declaration)
 
                                case INITIALIZER_STRING: {
                                        initializer_string_t *const string = &initializer->string;
-                                       cnst->conste.v.int_value = strlen(string->string) + 1;
+                                       cnst->conste.v.int_value = string->string.size;
                                        break;
                                }
 
@@ -2495,7 +2540,7 @@ static void parse_init_declarator_rest(declaration_t *declaration)
                }
        }
 
-       if(type != NULL && is_type_function(type)) {
+       if(is_type_function(type)) {
                errorf(declaration->source_position,
                       "initializers not allowed for function types at declator '%Y' (type '%T')",
                       declaration->symbol, orig_type);
@@ -2511,8 +2556,7 @@ static void parse_anonymous_declaration_rest(
 {
        eat(';');
 
-       declaration_t *declaration = allocate_ast_zero(sizeof(declaration[0]));
-
+       declaration_t *const declaration = allocate_declaration_zero();
        declaration->type            = specifiers->type;
        declaration->storage_class   = specifiers->storage_class;
        declaration->source_position = specifiers->source_position;
@@ -2553,7 +2597,8 @@ static void parse_declaration_rest(declaration_t *ndeclaration,
                type_t *orig_type = declaration->type;
                type_t *type      = skip_typeref(orig_type);
 
-               if(type->kind != TYPE_FUNCTION && declaration->is_inline) {
+               if(is_type_valid(type) &&
+                  type->kind != TYPE_FUNCTION && declaration->is_inline) {
                        warningf(declaration->source_position,
                                 "variable '%Y' declared 'inline'\n", declaration->symbol);
                }
@@ -2694,6 +2739,31 @@ static void parse_kr_declaration_list(declaration_t *declaration)
        declaration->type = type;
 }
 
+/**
+ * Check if all labels are defined in the current function.
+ */
+static void check_for_missing_labels(void)
+{
+       bool first_err = true;
+       for (const goto_statement_t *goto_statement = goto_first;
+            goto_statement != NULL;
+            goto_statement = goto_statement->next) {
+                const declaration_t *label = goto_statement->label;
+
+                if (label->source_position.input_name == NULL) {
+                        if (first_err) {
+                                first_err = false;
+                                diagnosticf("%s: In function '%Y':\n",
+                                        current_function->source_position.input_name,
+                                        current_function->symbol);
+                        }
+                        errorf(goto_statement->statement.source_position,
+                                "label '%Y' used but not defined", label->symbol);
+                }
+       }
+       goto_first = goto_last = NULL;
+}
+
 static void parse_external_declaration(void)
 {
        /* function-definitions and declarations both start with declaration
@@ -2787,6 +2857,7 @@ static void parse_external_declaration(void)
                current_function                    = declaration;
 
                declaration->init.statement = parse_compound_statement();
+               check_for_missing_labels();
 
                assert(current_function == declaration);
                current_function = old_current_function;
@@ -2822,15 +2893,12 @@ static void parse_struct_declarators(const declaration_specifiers_t *specifiers)
 
                        type_t *type = make_bitfield_type(base_type, size);
 
-                       declaration = allocate_ast_zero(sizeof(declaration[0]));
-
+                       declaration = allocate_declaration_zero();
                        declaration->namespc         = NAMESPACE_NORMAL;
                        declaration->storage_class   = STORAGE_CLASS_NONE;
                        declaration->source_position = token.source_position;
                        declaration->modifiers       = specifiers->decl_modifiers;
                        declaration->type            = type;
-
-                       record_declaration(declaration);
                } else {
                        declaration = parse_declarator(specifiers,/*may_be_abstract=*/true);
 
@@ -2912,10 +2980,15 @@ static expression_t *create_invalid_expression(void)
        return expression;
 }
 
+/**
+ * Prints an error message if an expression was expected but not read
+ */
 static expression_t *expected_expression_error(void)
 {
-       errorf(HERE, "expected expression, got token '%K'", &token);
-
+       /* skip the error message if the error token was read */
+       if (token.type != T_ERROR) {
+               errorf(HERE, "expected expression, got token '%K'", &token);
+       }
        next_token();
 
        return create_invalid_expression();
@@ -2985,8 +3058,7 @@ static declaration_t *create_implicit_function(symbol_t *symbol,
                free_type(ntype);
        }
 
-       declaration_t *declaration = allocate_ast_zero(sizeof(declaration[0]));
-
+       declaration_t *const declaration = allocate_declaration_zero();
        declaration->storage_class   = STORAGE_CLASS_EXTERN;
        declaration->type            = type;
        declaration->symbol          = symbol;
@@ -3266,7 +3338,6 @@ static expression_t *parse_function_keyword(void)
 
        expression->expression.kind     = EXPR_FUNCTION;
        expression->expression.datatype = type_string;
-       expression->value               = current_function->symbol->string;
 
        return (expression_t*) expression;
 }
@@ -3285,7 +3356,6 @@ static expression_t *parse_pretty_function_keyword(void)
 
        expression->expression.kind     = EXPR_PRETTY_FUNCTION;
        expression->expression.datatype = type_string;
-       expression->value               = current_function->symbol->string;
 
        return (expression_t*) expression;
 }
@@ -3610,7 +3680,7 @@ static void check_for_char_index_type(const expression_t *expression) {
        type_t *base_type = skip_typeref(type);
 
        if (base_type->base.kind == TYPE_ATOMIC) {
-               if (base_type->atomic.akind == ATOMIC_TYPE_CHAR) {
+               switch (base_type->atomic.akind == ATOMIC_TYPE_CHAR) {
                        warningf(expression->base.source_position,
                                "array subscript has type '%T'", type);
                }
@@ -3795,7 +3865,7 @@ static expression_t *parse_call_expression(unsigned precedence,
 
        function_type_t *function_type = NULL;
        type_t          *orig_type     = expression->base.datatype;
-       if(orig_type != NULL) {
+       if(is_type_valid(orig_type)) {
                type_t *type  = skip_typeref(orig_type);
 
                if(is_type_pointer(type)) {
@@ -3919,9 +3989,9 @@ static expression_t *parse_conditional_expression(unsigned precedence,
 
        /* 6.5.15.2 */
        type_t *condition_type_orig = expression->base.datatype;
-       if(condition_type_orig != NULL) {
+       if(is_type_valid(condition_type_orig)) {
                type_t *condition_type = skip_typeref(condition_type_orig);
-               if(condition_type != NULL && !is_type_scalar(condition_type)) {
+               if(condition_type->kind != TYPE_ERROR && !is_type_scalar(condition_type)) {
                        type_error("expected a scalar type in conditional condition",
                                   expression->base.source_position, condition_type_orig);
                }
@@ -3936,7 +4006,7 @@ static expression_t *parse_conditional_expression(unsigned precedence,
 
        type_t *orig_true_type  = true_expression->base.datatype;
        type_t *orig_false_type = false_expression->base.datatype;
-       if(orig_true_type == NULL || orig_false_type == NULL)
+       if(!is_type_valid(orig_true_type) || !is_type_valid(orig_false_type))
                return result;
 
        type_t *true_type  = skip_typeref(orig_true_type);
@@ -4004,7 +4074,7 @@ static expression_t *parse_builtin_classify_type(const unsigned precedence)
 static void semantic_incdec(unary_expression_t *expression)
 {
        type_t *orig_type = expression->value->base.datatype;
-       if(orig_type == NULL)
+       if(!is_type_valid(orig_type))
                return;
 
        type_t *type = skip_typeref(orig_type);
@@ -4020,7 +4090,7 @@ static void semantic_incdec(unary_expression_t *expression)
 static void semantic_unexpr_arithmetic(unary_expression_t *expression)
 {
        type_t *orig_type = expression->value->base.datatype;
-       if(orig_type == NULL)
+       if(!is_type_valid(orig_type))
                return;
 
        type_t *type = skip_typeref(orig_type);
@@ -4036,7 +4106,7 @@ static void semantic_unexpr_arithmetic(unary_expression_t *expression)
 static void semantic_unexpr_scalar(unary_expression_t *expression)
 {
        type_t *orig_type = expression->value->base.datatype;
-       if(orig_type == NULL)
+       if(!is_type_valid(orig_type))
                return;
 
        type_t *type = skip_typeref(orig_type);
@@ -4051,7 +4121,7 @@ static void semantic_unexpr_scalar(unary_expression_t *expression)
 static void semantic_unexpr_integer(unary_expression_t *expression)
 {
        type_t *orig_type = expression->value->base.datatype;
-       if(orig_type == NULL)
+       if(!is_type_valid(orig_type))
                return;
 
        type_t *type = skip_typeref(orig_type);
@@ -4066,7 +4136,7 @@ static void semantic_unexpr_integer(unary_expression_t *expression)
 static void semantic_dereference(unary_expression_t *expression)
 {
        type_t *orig_type = expression->value->base.datatype;
-       if(orig_type == NULL)
+       if(!is_type_valid(orig_type))
                return;
 
        type_t *type = skip_typeref(orig_type);
@@ -4091,7 +4161,7 @@ static void semantic_take_addr(unary_expression_t *expression)
        value->base.datatype = revert_automatic_type_conversion(value);
 
        type_t *orig_type = value->base.datatype;
-       if(orig_type == NULL)
+       if(!is_type_valid(orig_type))
                return;
 
        if(value->kind == EXPR_REFERENCE) {
@@ -4491,7 +4561,15 @@ static void semantic_binexpr_assign(binary_expression_t *expression)
                return;
        }
 
-       semantic_assign(orig_type_left, &expression->right, "assignment");
+       type_t *const res_type = semantic_assign(orig_type_left, expression->right,
+                                                "assignment");
+       if (res_type == NULL) {
+               errorf(expression->expression.source_position,
+                       "cannot assign to '%T' from '%T'",
+                       orig_type_left, expression->right->base.datatype);
+       } else {
+               expression->right = create_implicit_cast(expression->right, res_type);
+       }
 
        expression->expression.datatype = orig_type_left;
 }
@@ -4858,23 +4936,44 @@ static statement_t *parse_case_statement(void)
 
        expect(':');
 
-       if (current_switch != NULL) {
-               /* link all cases into the switch statement */
-               if (current_switch->last_case == NULL) {
-                       current_switch->first_case =
-                       current_switch->last_case  = &statement->case_label;
+       if (! is_constant_expression(statement->case_label.expression)) {
+               errorf(statement->base.source_position,
+                       "case label does not reduce to an integer constant");
+       } else {
+               /* TODO: check if the case label is already known */
+               if (current_switch != NULL) {
+                       /* link all cases into the switch statement */
+                       if (current_switch->last_case == NULL) {
+                               current_switch->first_case =
+                               current_switch->last_case  = &statement->case_label;
+                       } else {
+                               current_switch->last_case->next = &statement->case_label;
+                       }
                } else {
-                       current_switch->last_case->next = &statement->case_label;
+                       errorf(statement->base.source_position,
+                               "case label not within a switch statement");
                }
-       } else {
-               errorf(statement->base.source_position,
-                       "case label not within a switch statement");
        }
        statement->case_label.label_statement = parse_statement();
 
        return statement;
 }
 
+/**
+ * Finds an existing default label of a switch statement.
+ */
+static case_label_statement_t *
+find_default_label(const switch_statement_t *statement)
+{
+       for (case_label_statement_t *label = statement->first_case;
+            label != NULL;
+                label = label->next) {
+               if (label->expression == NULL)
+                       return label;
+       }
+       return NULL;
+}
+
 /**
  * Parse a default statement.
  */
@@ -4887,6 +4986,25 @@ static statement_t *parse_default_statement(void)
        statement->base.source_position = token.source_position;
 
        expect(':');
+       if (current_switch != NULL) {
+               const case_label_statement_t *def_label = find_default_label(current_switch);
+               if (def_label != NULL) {
+                       errorf(HERE, "multiple default labels in one switch");
+                       errorf(def_label->statement.source_position,
+                               "this is the first default label");
+               } else {
+                       /* link all cases into the switch statement */
+                       if (current_switch->last_case == NULL) {
+                               current_switch->first_case =
+                                       current_switch->last_case  = &statement->case_label;
+                       } else {
+                               current_switch->last_case->next = &statement->case_label;
+                       }
+               }
+       } else {
+               errorf(statement->base.source_position,
+                       "'default' label not within a switch statement");
+       }
        statement->label.label_statement = parse_statement();
 
        return statement;
@@ -4907,7 +5025,7 @@ static declaration_t *get_label(symbol_t *symbol)
        }
 
        /* otherwise we need to create a new one */
-       declaration_t *declaration = allocate_ast_zero(sizeof(declaration[0]));
+       declaration_t *const declaration = allocate_declaration_zero();
        declaration->namespc       = NAMESPACE_LABEL;
        declaration->symbol        = symbol;
 
@@ -5005,6 +5123,15 @@ static statement_t *parse_switch(void)
        return (statement_t*) statement;
 }
 
+static statement_t *parse_loop_body(statement_t *const loop)
+{
+       statement_t *const rem = current_loop;
+       current_loop = loop;
+       statement_t *const body = parse_statement();
+       current_loop = rem;
+       return body;
+}
+
 /**
  * Parse a while statement.
  */
@@ -5016,18 +5143,13 @@ static statement_t *parse_while(void)
        statement->statement.kind            = STATEMENT_WHILE;
        statement->statement.source_position = token.source_position;
 
-       statement_t *rem = current_loop;
-       expect_fail('(');
+       expect('(');
        statement->condition = parse_expression();
-       expect_fail(')');
+       expect(')');
 
-       statement->body = parse_statement();
-       current_loop = rem;
+       statement->body = parse_loop_body((statement_t*)statement);
 
        return (statement_t*) statement;
-fail:
-       current_loop = rem;
-       return NULL;
 }
 
 /**
@@ -5041,19 +5163,14 @@ static statement_t *parse_do(void)
        statement->statement.kind            = STATEMENT_DO_WHILE;
        statement->statement.source_position = token.source_position;
 
-       statement_t *rem = current_loop;
-       statement->body = parse_statement();
-       expect_fail(T_while);
-       expect_fail('(');
+       statement->body = parse_loop_body((statement_t*)statement);
+       expect(T_while);
+       expect('(');
        statement->condition = parse_expression();
-       expect_fail(')');
-       current_loop = rem;
+       expect(')');
        expect(';');
 
        return (statement_t*) statement;
-fail:
-       current_loop = rem;
-       return NULL;
 }
 
 /**
@@ -5069,7 +5186,6 @@ static statement_t *parse_for(void)
 
        expect('(');
 
-       statement_t *rem = current_loop;
        int         top          = environment_top();
        context_t  *last_context = context;
        set_context(&statement->context);
@@ -5079,31 +5195,27 @@ static statement_t *parse_for(void)
                        parse_declaration(record_declaration);
                } else {
                        statement->initialisation = parse_expression();
-                       expect_fail(';');
+                       expect(';');
                }
        } else {
-               expect_fail(';');
+               expect(';');
        }
 
        if(token.type != ';') {
                statement->condition = parse_expression();
        }
-       expect_fail(';');
+       expect(';');
        if(token.type != ')') {
                statement->step = parse_expression();
        }
-       expect_fail(')');
-       statement->body = parse_statement();
+       expect(')');
+       statement->body = parse_loop_body((statement_t*)statement);
 
        assert(context == &statement->context);
        set_context(last_context);
        environment_pop_to(top);
-       current_loop = rem;
 
        return (statement_t*) statement;
-fail:
-       current_loop = rem;
-       return NULL;
 }
 
 /**
@@ -5130,6 +5242,13 @@ static statement_t *parse_goto(void)
 
        statement->label = label;
 
+       /* remember the goto's in a list for later checking */
+       if (goto_last == NULL) {
+               goto_first = goto_last = statement;
+       } else {
+               goto_last->next = statement;
+       }
+
        expect(';');
 
        return (statement_t*) statement;
@@ -5140,18 +5259,19 @@ static statement_t *parse_goto(void)
  */
 static statement_t *parse_continue(void)
 {
-       eat(T_continue);
-       expect(';');
-
-       statement_t *statement          = allocate_ast_zero(sizeof(statement[0]));
-       statement->kind                 = STATEMENT_CONTINUE;
-       statement->base.source_position = token.source_position;
-
+       statement_t *statement;
        if (current_loop == NULL) {
                errorf(HERE, "continue statement not within loop");
-               return NULL;
+               statement = NULL;
+       } else {
+               statement = allocate_statement_zero(STATEMENT_CONTINUE);
+
+               statement->base.source_position = token.source_position;
        }
 
+       eat(T_continue);
+       expect(';');
+
        return statement;
 }
 
@@ -5160,17 +5280,19 @@ static statement_t *parse_continue(void)
  */
 static statement_t *parse_break(void)
 {
-       eat(T_break);
-       expect(';');
-
-       statement_t *statement          = allocate_ast_zero(sizeof(statement[0]));
-       statement->kind                 = STATEMENT_BREAK;
-       statement->base.source_position = token.source_position;
-
+       statement_t *statement;
        if (current_switch == NULL && current_loop == NULL) {
                errorf(HERE, "break statement not within loop or switch");
-               return NULL;
+               statement = NULL;
+       } else {
+               statement = allocate_statement_zero(STATEMENT_BREAK);
+
+               statement->base.source_position = token.source_position;
        }
+
+       eat(T_break);
+       expect(';');
+
        return statement;
 }
 
@@ -5244,8 +5366,20 @@ static statement_t *parse_return(void)
                                "'return' with a value, in function returning void");
                        return_value = NULL;
                } else {
-                       if(return_type != NULL) {
-                               semantic_assign(return_type, &return_value, "'return'");
+                       if(is_type_valid(return_type)) {
+                               if (return_value->base.datatype == NULL)
+                                       return (statement_t*)statement;
+
+                               type_t *const res_type = semantic_assign(return_type,
+                                       return_value, "'return'");
+                               if (res_type == NULL) {
+                                       errorf(statement->statement.source_position,
+                                               "cannot assign to '%T' from '%T'",
+                                               "cannot return something of type '%T' in function returning '%T'",
+                                               return_value->base.datatype, return_type);
+                               } else {
+                                       return_value = create_implicit_cast(return_value, res_type);
+                               }
                        }
                }
                /* check for returning address of a local var */