C: Detect all variably modified types [PR108375]

Some variably modified types were not detected correctly.
Define C_TYPE_VARIABLY_MODIFIED via TYPE_LANG_FLAG 6 in the CFE.
This flag records whether a type is variably modified and is
set for all such types including arrays with variably modified
element type or structures and unions with variably modified
members. This is then used to detect such types in the C FE
and middle-end (via the existing language hook).

gcc/c/ChangeLog:
	PR c/108375
	* c-decl.cc (decl_jump_unsafe): Use c_type_variably_modified_p.
	(diagnose_mismatched_decl): Dito.
	(warn_about_goto): Dito:
	(c_check_switch_jump_warnings): Dito.
	(finish_decl): Dito.
	(finish_struct): Dito.
	(grokdeclarator): Set C_TYPE_VARIABLY_MODIFIED.
	(finish_struct): Set C_TYPE_VARIABLY_MODIFIED.
	* c-objc-common.cc (c_var_mod_p): New function.
	(c_var_unspec_p): Remove.
	* c-objc-common.h: Set lang hook.
	* c-parser.cc (c_parser_declararion_or_fndef): Use c_type_variably_modified_p.
	(c_parser_typeof_specifier): Dito.
	(c_parser_has_attribute_expression): Dito.
	(c_parser_generic_selection): Dito.
	* c-tree.h: Define C_TYPE_VARIABLY_MODIFIED and define c_var_mode_p.
	* c-typeck.cc: Remove c_vla_mod_p and use C_TYPE_VARIABLY_MODIFIED.

gcc/testsuite/ChangeLog:
	PR c/108375
	* gcc.dg/pr108375-1.c: New test.
	* gcc.dg/pr108375-2.c: New test.

1 files changed, 14 insertions, 2 deletions

diff --git a/gcc/c/c-tree.h b/gcc/c/c-tree.h
index e5eefe6..e6b6fe9 100644
--- a/gcc/c/c-tree.h
+++ b/gcc/c/c-tree.h
@@ -59,6 +59,10 @@ along with GCC; see the file COPYING3.  If not see
 #define C_TYPE_VARIABLE_SIZE(TYPE) TYPE_LANG_FLAG_1 (TYPE)
 #define C_DECL_VARIABLE_SIZE(TYPE) DECL_LANG_FLAG_0 (TYPE)
 
+/* Record whether a type is variably modified. */
+#define C_TYPE_VARIABLY_MODIFIED(TYPE) TYPE_LANG_FLAG_6 (TYPE)
+
+
 /* Record whether a type is defined inside a struct or union type.
    This is used for -Wc++-compat. */
 #define C_TYPE_DEFINED_IN_STRUCT(TYPE) TYPE_LANG_FLAG_2 (TYPE)
@@ -714,7 +718,7 @@ extern bool c_objc_common_init (void);
 extern bool c_missing_noreturn_ok_p (tree);
 extern bool c_warn_unused_global_decl (const_tree);
 extern void c_initialize_diagnostics (diagnostic_context *);
-extern bool c_vla_unspec_p (tree x, tree fn);
+extern bool c_var_mod_p (tree x, tree fn);
 extern alias_set_type c_get_alias_set (tree);
 
 /* in c-typeck.cc */
@@ -729,6 +733,15 @@ extern location_t c_last_sizeof_loc;
 extern struct c_switch *c_switch_stack;
 
 extern bool null_pointer_constant_p (const_tree);
+
+
+inline
+bool c_type_variably_modified_p (tree t)
+{
+  return error_mark_node != t && C_TYPE_VARIABLY_MODIFIED (t);
+}
+
+
 extern bool char_type_p (tree);
 extern tree c_objc_common_truthvalue_conversion (location_t, tree);
 extern tree require_complete_type (location_t, tree);
@@ -736,7 +749,6 @@ extern bool same_translation_unit_p (const_tree, const_tree);
 extern int comptypes (tree, tree);
 extern int comptypes_check_different_types (tree, tree, bool *);
 extern int comptypes_check_enum_int (tree, tree, bool *);
-extern bool c_vla_type_p (const_tree);
 extern bool c_mark_addressable (tree, bool = false);
 extern void c_incomplete_type_error (location_t, const_tree, const_tree);
 extern tree c_type_promotes_to (tree);