+bool is_constant_initializer(const initializer_t *initializer)
+{
+ switch(initializer->kind) {
+ case INITIALIZER_STRING:
+ case INITIALIZER_WIDE_STRING:
+ case INITIALIZER_DESIGNATOR:
+ return true;
+
+ case INITIALIZER_VALUE:
+ return is_constant_expression(initializer->value.value);
+
+ case INITIALIZER_LIST:
+ for(size_t i = 0; i < initializer->list.len; ++i) {
+ initializer_t *sub_initializer = initializer->list.initializers[i];
+ if(!is_constant_initializer(sub_initializer))
+ return false;
+ }
+ return true;
+ }
+ panic("invalid initializer kind found");
+}
+
+static bool is_object_with_constant_address(const expression_t *expression)
+{
+ switch(expression->kind) {
+ case EXPR_UNARY_DEREFERENCE:
+ return is_address_constant(expression->unary.value);
+
+ case EXPR_SELECT: {
+ if(is_type_pointer(expression->select.compound->base.type)) {
+ /* it's a -> */
+ return is_address_constant(expression->select.compound);
+ } else {
+ return is_object_with_constant_address(expression->select.compound);
+ }
+ }
+
+ case EXPR_ARRAY_ACCESS:
+ return is_constant_expression(expression->array_access.index)
+ && is_address_constant(expression->array_access.array_ref);
+
+ case EXPR_REFERENCE: {
+ declaration_t *declaration = expression->reference.declaration;
+ switch((storage_class_tag_t) declaration->storage_class) {
+ case STORAGE_CLASS_NONE:
+ case STORAGE_CLASS_EXTERN:
+ case STORAGE_CLASS_STATIC:
+ return true;
+ default:
+ return false;
+ }
+ }
+
+ default:
+ return false;
+ }
+}
+
+bool is_address_constant(const expression_t *expression)
+{
+ switch(expression->kind) {
+ case EXPR_UNARY_TAKE_ADDRESS:
+ return is_object_with_constant_address(expression->unary.value);
+
+ case EXPR_UNARY_DEREFERENCE: {
+ type_t *real_type = revert_automatic_type_conversion(expression->unary.value);
+ /* dereferencing a function is a NOP */
+ if(is_type_function(real_type)) {
+ return is_address_constant(expression->unary.value);
+ }
+ }
+
+ case EXPR_UNARY_CAST:
+ return is_type_pointer(skip_typeref(expression->base.type))
+ && (is_constant_expression(expression->unary.value)
+ || is_address_constant(expression->unary.value));
+
+ case EXPR_BINARY_ADD:
+ case EXPR_BINARY_SUB: {
+ expression_t *left = expression->binary.left;
+ expression_t *right = expression->binary.right;
+
+ if(is_type_pointer(skip_typeref(left->base.type))) {
+ return is_address_constant(left) && is_constant_expression(right);
+ } else if(is_type_pointer(skip_typeref(right->base.type))) {
+ return is_constant_expression(left) && is_address_constant(right);
+ }
+
+ return false;
+ }
+
+ case EXPR_REFERENCE: {
+ declaration_t *declaration = expression->reference.declaration;
+ type_t *type = skip_typeref(declaration->type);
+ if(is_type_function(type))
+ return true;
+ if(is_type_array(type)) {
+ return is_object_with_constant_address(expression);
+ }
+ return false;
+ }
+
+ default:
+ return false;
+ }
+}
+
+bool is_constant_expression(const expression_t *expression)
+{
+ switch(expression->kind) {
+
+ case EXPR_CONST:
+ case EXPR_CHARACTER_CONSTANT:
+ case EXPR_WIDE_CHARACTER_CONSTANT:
+ case EXPR_STRING_LITERAL:
+ case EXPR_WIDE_STRING_LITERAL:
+ case EXPR_SIZEOF:
+ case EXPR_CLASSIFY_TYPE:
+ case EXPR_FUNCTION:
+ case EXPR_FUNCSIG:
+ case EXPR_FUNCDNAME:
+ case EXPR_PRETTY_FUNCTION:
+ case EXPR_OFFSETOF:
+ case EXPR_ALIGNOF:
+ case EXPR_BUILTIN_CONSTANT_P:
+ return true;
+
+ case EXPR_BUILTIN_SYMBOL:
+ case EXPR_BUILTIN_PREFETCH:
+ case EXPR_CALL:
+ case EXPR_SELECT:
+ case EXPR_VA_START:
+ case EXPR_VA_ARG:
+ case EXPR_STATEMENT:
+ case EXPR_UNARY_POSTFIX_INCREMENT:
+ case EXPR_UNARY_POSTFIX_DECREMENT:
+ case EXPR_UNARY_PREFIX_INCREMENT:
+ case EXPR_UNARY_PREFIX_DECREMENT:
+ case EXPR_UNARY_BITFIELD_EXTRACT:
+ case EXPR_UNARY_ASSUME: /* has VOID type */
+ case EXPR_UNARY_TAKE_ADDRESS:
+ case EXPR_UNARY_DEREFERENCE:
+ case EXPR_BINARY_ASSIGN:
+ case EXPR_BINARY_MUL_ASSIGN:
+ case EXPR_BINARY_DIV_ASSIGN:
+ case EXPR_BINARY_MOD_ASSIGN:
+ case EXPR_BINARY_ADD_ASSIGN:
+ case EXPR_BINARY_SUB_ASSIGN:
+ case EXPR_BINARY_SHIFTLEFT_ASSIGN:
+ case EXPR_BINARY_SHIFTRIGHT_ASSIGN:
+ case EXPR_BINARY_BITWISE_AND_ASSIGN:
+ case EXPR_BINARY_BITWISE_XOR_ASSIGN:
+ case EXPR_BINARY_BITWISE_OR_ASSIGN:
+ case EXPR_BINARY_COMMA:
+ return false;
+
+ case EXPR_UNARY_NEGATE:
+ case EXPR_UNARY_PLUS:
+ case EXPR_UNARY_BITWISE_NEGATE:
+ case EXPR_UNARY_NOT:
+ return is_constant_expression(expression->unary.value);
+
+ case EXPR_UNARY_CAST:
+ case EXPR_UNARY_CAST_IMPLICIT:
+ return is_type_arithmetic(skip_typeref(expression->base.type))
+ && is_constant_expression(expression->unary.value);
+
+ case EXPR_BINARY_ADD:
+ case EXPR_BINARY_SUB:
+ case EXPR_BINARY_MUL:
+ case EXPR_BINARY_DIV:
+ case EXPR_BINARY_MOD:
+ case EXPR_BINARY_EQUAL:
+ case EXPR_BINARY_NOTEQUAL:
+ case EXPR_BINARY_LESS:
+ case EXPR_BINARY_LESSEQUAL:
+ case EXPR_BINARY_GREATER:
+ case EXPR_BINARY_GREATEREQUAL:
+ case EXPR_BINARY_BITWISE_AND:
+ case EXPR_BINARY_BITWISE_OR:
+ case EXPR_BINARY_BITWISE_XOR:
+ case EXPR_BINARY_LOGICAL_AND:
+ case EXPR_BINARY_LOGICAL_OR:
+ case EXPR_BINARY_SHIFTLEFT:
+ case EXPR_BINARY_SHIFTRIGHT:
+ case EXPR_BINARY_BUILTIN_EXPECT:
+ case EXPR_BINARY_ISGREATER:
+ case EXPR_BINARY_ISGREATEREQUAL:
+ case EXPR_BINARY_ISLESS:
+ case EXPR_BINARY_ISLESSEQUAL:
+ case EXPR_BINARY_ISLESSGREATER:
+ case EXPR_BINARY_ISUNORDERED:
+ return is_constant_expression(expression->binary.left)
+ && is_constant_expression(expression->binary.right);
+
+ case EXPR_COMPOUND_LITERAL:
+ return is_constant_initializer(expression->compound_literal.initializer);
+
+ case EXPR_CONDITIONAL: {
+ expression_t *condition = expression->conditional.condition;
+ if(!is_constant_expression(condition))
+ return false;
+
+ long val = fold_constant(condition);
+ if(val != 0)
+ return is_constant_expression(expression->conditional.true_expression);
+ else
+ return is_constant_expression(expression->conditional.false_expression);
+ }
+
+ case EXPR_ARRAY_ACCESS:
+ return is_constant_expression(expression->array_access.array_ref)
+ && is_constant_expression(expression->array_access.index);
+
+ case EXPR_REFERENCE: {
+ declaration_t *declaration = expression->reference.declaration;
+ if(declaration->storage_class == STORAGE_CLASS_ENUM_ENTRY)
+ return true;
+
+ return false;
+ }
+
+ case EXPR_INVALID:
+ return true;
+
+ case EXPR_UNKNOWN:
+ break;
+ }
+ panic("invalid expression found (is constant expression)");
+}
+
+/**
+ * Initialize the AST construction.
+ */