[gcc r12-1264] Fix old thinko in warning on pointer for storage order purposes

[gcc r12-1264] Fix old thinko in warning on pointer for storage order purposes

[Eric Botcazou]

https://gcc.gnu.org/g:97d83259b91fb558f5b09bfb09529900f585c4c9

commit r12-1264-g97d83259b91fb558f5b09bfb09529900f585c4c9
Author: Eric Botcazou <ebotcazou@adacore.com>
Date:   Mon Jun 7 18:17:31 2021 +0200

    Fix old thinko in warning on pointer for storage order purposes
    
    gcc/c
            PR c/100920
            * c-typeck.c (convert_for_assignment): Test fndecl_built_in_p to
            spot built-in functions.
    gcc/testsuite/
            * gcc.dg/sso-14.c: Adjust.

Diff:
---
 gcc/c/c-typeck.c              | 2 +-
 gcc/testsuite/gcc.dg/sso-14.c | 7 +++++--
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/gcc/c/c-typeck.c b/gcc/c/c-typeck.c
index daa2e12a25f..845d50f3310 100644
--- a/gcc/c/c-typeck.c
+++ b/gcc/c/c-typeck.c
@@ -7303,7 +7303,7 @@ convert_for_assignment (location_t location, location_t expr_loc, tree type,
 	    /* Do not warn for built-in functions, for example memcpy, since we
 	       control how they behave and they can be useful in this area.  */
 	    if (TREE_CODE (rname) != FUNCTION_DECL
-		|| !DECL_IS_UNDECLARED_BUILTIN (rname))
+		|| !fndecl_built_in_p (rname))
 	      warning_at (location, OPT_Wscalar_storage_order,
 			  "passing argument %d of %qE from incompatible "
 			  "scalar storage order", parmnum, rname);
diff --git a/gcc/testsuite/gcc.dg/sso-14.c b/gcc/testsuite/gcc.dg/sso-14.c
index af98145569e..8941946c3ab 100644
--- a/gcc/testsuite/gcc.dg/sso-14.c
+++ b/gcc/testsuite/gcc.dg/sso-14.c
@@ -5,6 +5,7 @@
 
 #include <stddef.h>
 #include <stdlib.h>
+#include <string.h>
 
 #if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
 #define REV_ENDIANNESS __attribute__((scalar_storage_order("big-endian")))
@@ -42,12 +43,14 @@ int main(void)
 {
   t_s12 *msg1 = __builtin_alloca(10);
   t_u12 *msg2 = __builtin_alloca(10);
+  int same;
 
   msg1 = malloc (sizeof (t_s12));
   msg2 = malloc (sizeof (t_u12));
 
-  msg1->a[0].val = 0;
-  msg2->a[0].val = 0;
+  memset (msg1, 0, sizeof (t_s12));
+  memcpy (msg2, &msg1, sizeof (t_s12));
+  same = memcmp (msg1, msg2, sizeof (t_s12));
 
   return 0;
 }