c: Reject _Atomic type * as last argument to __builtin_*_overflow [PR90628]

During the __builtin_clear_padding implementation, I've noticed we don't
diagnose _Atomic whatever * as last argument to __builtin_*_overflow.
As the storing by that builtin isn't atomic in any way, I think we should
reject it.

2020-11-17  Jakub Jelinek  <jakub@redhat.com>

	PR c/90628
	* c-common.c (check_builtin_function_arguments)
	<case BUILT_IN_ADD_OVERFLOW>: Diagnose when last argument is pointer
	to _Atomic.  For the TYPE_READONLY case, adjust message to be usable
	for more builtins and argument positions.

	* gcc.dg/builtin-arith-overflow-4.c: New test.

2 files changed, 52 insertions, 2 deletions

diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c
index ab7f642..729bd85 100644
--- a/gcc/c-family/c-common.c
+++ b/gcc/c-family/c-common.c
@@ -6133,11 +6133,18 @@ check_builtin_function_arguments (location_t loc, vec<location_t> arg_loc,
 	    }
 	  else if (TYPE_READONLY (TREE_TYPE (TREE_TYPE (args[2]))))
 	    {
-	      error_at (ARG_LOCATION (2), "argument 3 in call to function %qE "
-			"has pointer to %<const%> type (%qT)", fndecl,
+	      error_at (ARG_LOCATION (2), "argument %u in call to function %qE "
+			"has pointer to %qs type (%qT)", 3, fndecl, "const",
 			TREE_TYPE (args[2]));
 	      return false;
 	    }
+	  else if (TYPE_ATOMIC (TREE_TYPE (TREE_TYPE (args[2]))))
+	    {
+	      error_at (ARG_LOCATION (2), "argument %u in call to function %qE "
+			"has pointer to %qs type (%qT)", 3, fndecl,
+			"_Atomic", TREE_TYPE (args[2]));
+	      return false;
+	    }
 	  return true;
 	}
       return false;
diff --git a/gcc/testsuite/gcc.dg/builtin-arith-overflow-4.c b/gcc/testsuite/gcc.dg/builtin-arith-overflow-4.c
new file mode 100644
index 0000000..ab7d82a
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/builtin-arith-overflow-4.c
@@ -0,0 +1,43 @@
+/* PR c/90628 */
+/* { dg-do compile } */
+/* { dg-options "" } */
+
+_Atomic int a = 1, b = 2, c = 3;
+_Atomic long d = 4, e = 5, f = 6;
+_Atomic long long g = 7, h = 8, i = 9;
+
+void
+f1 ()
+{
+  __builtin_add_overflow (a, b, &c);	/* { dg-error "argument 3 in call to function '__builtin_add_overflow' has pointer to '_Atomic' type" } */
+}
+
+void
+f2 ()
+{
+  __builtin_sub_overflow (d, e, &f);	/* { dg-error "argument 3 in call to function '__builtin_sub_overflow' has pointer to '_Atomic' type" } */
+}
+
+void
+f3 ()
+{
+  __builtin_mul_overflow (g, h, &i);	/* { dg-error "argument 3 in call to function '__builtin_mul_overflow' has pointer to '_Atomic' type" } */
+}
+
+void
+f4 ()
+{
+  __builtin_sadd_overflow (a, b, &c);	/* { dg-warning "passing argument 3 of '__builtin_sadd_overflow' from incompatible pointer type" } */
+}
+
+void
+f5 ()
+{
+  __builtin_ssubl_overflow (d, e, &f);	/* { dg-warning "passing argument 3 of '__builtin_ssubl_overflow' from incompatible pointer type" } */
+}
+
+void
+f6 ()
+{
+  __builtin_smulll_overflow (g, h, &i);	/* { dg-warning "passing argument 3 of '__builtin_smulll_overflow' from incompatible pointer type" } */
+}