C: Do not drop qualifiers in typeof for _Atomic types. [PR65455,PR92935]

2020-11-25  Martin Uecker  <muecker@gwdg.de>

gcc/c/
	PR c/65455
	PR c/92935
	* c-parser.c (c_parser_declaration_or_fndef): Remove
	redundant code to drop qualifiers of _Atomic types for __auto_type.
	(c_parser_typeof_specifier): Do not drop qualifiers of _Atomic
	types for __typeof__.

gcc/
	PR c/65455
	PR c/92935
	* ginclude/stdatomic.h: Use comma operator to drop qualifiers.

gcc/testsuite/
	PR c/65455
	PR c/92935
	* gcc.dg/typeof-2.c: Adapt test.

3 files changed, 19 insertions, 24 deletions

diff --git a/gcc/c/c-parser.c b/gcc/c/c-parser.c
index d86098a..87ee8f4 100644
--- a/gcc/c/c-parser.c
+++ b/gcc/c/c-parser.c
@@ -2224,10 +2224,6 @@ c_parser_declaration_or_fndef (c_parser *parser, bool fndef_ok,
 			      " initializer");
 		  init = convert_lvalue_to_rvalue (init_loc, init, true, true);
 		  tree init_type = TREE_TYPE (init.value);
-		  /* As with typeof, remove all qualifiers from atomic types.  */
-		  if (init_type != error_mark_node && TYPE_ATOMIC (init_type))
-		    init_type
-		      = c_build_qualified_type (init_type, TYPE_UNQUALIFIED);
 		  bool vm_type = variably_modified_type_p (init_type,
 							   NULL_TREE);
 		  if (vm_type)
@@ -3743,11 +3739,6 @@ c_parser_typeof_specifier (c_parser *parser)
       if (was_vm)
 	ret.expr = c_fully_fold (expr.value, false, &ret.expr_const_operands);
       pop_maybe_used (was_vm);
-      /* For use in macros such as those in <stdatomic.h>, remove all
-	 qualifiers from atomic types.  (const can be an issue for more macros
-	 using typeof than just the <stdatomic.h> ones.)  */
-      if (ret.spec != error_mark_node && TYPE_ATOMIC (ret.spec))
-	ret.spec = c_build_qualified_type (ret.spec, TYPE_UNQUALIFIED);
     }
   parens.skip_until_found_close (parser);
   return ret;
diff --git a/gcc/ginclude/stdatomic.h b/gcc/ginclude/stdatomic.h
index b968164..7c2e08a 100644
--- a/gcc/ginclude/stdatomic.h
+++ b/gcc/ginclude/stdatomic.h
@@ -107,7 +107,7 @@ extern void atomic_signal_fence (memory_order);
 #define ATOMIC_POINTER_LOCK_FREE	__GCC_ATOMIC_POINTER_LOCK_FREE
 
 
-/* Note that these macros require __typeof__ and __auto_type to remove
+/* Note that these macros require __auto_type to remove
    _Atomic qualifiers (and const qualifiers, if those are valid on
    macro operands).
    
@@ -122,7 +122,7 @@ extern void atomic_signal_fence (memory_order);
   __extension__								\
   ({									\
     __auto_type __atomic_store_ptr = (PTR);				\
-    __typeof__ (*__atomic_store_ptr) __atomic_store_tmp = (VAL);	\
+    __typeof__ ((void)0, *__atomic_store_ptr) __atomic_store_tmp = (VAL);	\
     __atomic_store (__atomic_store_ptr, &__atomic_store_tmp, (MO));	\
   })
 
@@ -134,7 +134,7 @@ extern void atomic_signal_fence (memory_order);
   __extension__								\
   ({									\
     __auto_type __atomic_load_ptr = (PTR);				\
-    __typeof__ (*__atomic_load_ptr) __atomic_load_tmp;			\
+    __typeof__ ((void)0, *__atomic_load_ptr) __atomic_load_tmp;			\
     __atomic_load (__atomic_load_ptr, &__atomic_load_tmp, (MO));	\
     __atomic_load_tmp;							\
   })
@@ -146,8 +146,8 @@ extern void atomic_signal_fence (memory_order);
   __extension__								\
   ({									\
     __auto_type __atomic_exchange_ptr = (PTR);				\
-    __typeof__ (*__atomic_exchange_ptr) __atomic_exchange_val = (VAL);	\
-    __typeof__ (*__atomic_exchange_ptr) __atomic_exchange_tmp;		\
+    __typeof__ ((void)0, *__atomic_exchange_ptr) __atomic_exchange_val = (VAL);	\
+    __typeof__ ((void)0, *__atomic_exchange_ptr) __atomic_exchange_tmp;		\
     __atomic_exchange (__atomic_exchange_ptr, &__atomic_exchange_val,	\
 		       &__atomic_exchange_tmp, (MO));			\
     __atomic_exchange_tmp;						\
@@ -161,7 +161,7 @@ extern void atomic_signal_fence (memory_order);
   __extension__								\
   ({									\
     __auto_type __atomic_compare_exchange_ptr = (PTR);			\
-    __typeof__ (*__atomic_compare_exchange_ptr) __atomic_compare_exchange_tmp \
+    __typeof__ ((void)0, *__atomic_compare_exchange_ptr) __atomic_compare_exchange_tmp \
       = (DES);								\
     __atomic_compare_exchange (__atomic_compare_exchange_ptr, (VAL),	\
 			       &__atomic_compare_exchange_tmp, 0,	\
@@ -176,7 +176,7 @@ extern void atomic_signal_fence (memory_order);
   __extension__								\
   ({									\
     __auto_type __atomic_compare_exchange_ptr = (PTR);			\
-    __typeof__ (*__atomic_compare_exchange_ptr) __atomic_compare_exchange_tmp \
+    __typeof__ ((void)0, *__atomic_compare_exchange_ptr) __atomic_compare_exchange_tmp \
       = (DES);								\
     __atomic_compare_exchange (__atomic_compare_exchange_ptr, (VAL),	\
 			       &__atomic_compare_exchange_tmp, 1,	\
diff --git a/gcc/testsuite/gcc.dg/typeof-2.c b/gcc/testsuite/gcc.dg/typeof-2.c
index 21ef5b0..68f91c6 100644
--- a/gcc/testsuite/gcc.dg/typeof-2.c
+++ b/gcc/testsuite/gcc.dg/typeof-2.c
@@ -1,21 +1,23 @@
-/* Test qualifier discard of typeof for atomic types. */
+/* Test qualifier preservation of typeof and discarded for __auto_type. */
 /* { dg-do compile } */
 /* { dg-options "-std=c11" } */
 
-/* Check that the qualifiers are discarded for atomic types. */
+/* Check that the qualifiers are preserved for atomic types. */
 
 extern int i;
 
 extern int * p;
 
 extern int _Atomic const ci;
-extern __typeof (ci) i;
+extern __typeof (ci) ci;
 
 extern int _Atomic volatile vi;
-extern __typeof (vi) i;
+extern __typeof (vi) vi;
 
 extern int * _Atomic restrict ri;
-extern __typeof (ri) p;
+extern __typeof (ri) ri;
+
+/* Check that the qualifiers are discarded for atomic types. */
 
 void f(void)
 {
@@ -46,14 +48,16 @@ extern __typeof (nvi) k;
 extern int * restrict nri;
 extern __typeof (nri) q;
 
+/* Check that the qualifiers are discarded for non-atomic types. */
+
 void g(void)
 {
   __auto_type aci = nci;
-  int const *paci = &aci;
+  int *paci = &aci;
 
   __auto_type avi = nvi;
-  int volatile *pavi = &avi;
+  int *pavi = &avi;
 
   __auto_type ari = nri;
-  int * restrict *pari = &ari;
+  int **pari = &ari;
 }