[gcc r11-8533] Fix old thinko in warning on pointer for storage order purposes

[gcc r11-8533] Fix old thinko in warning on pointer for storage order purposes

[Eric Botcazou]

https://gcc.gnu.org/g:5be418dc591014b1773d59abca8fba5be34df618

commit r11-8533-g5be418dc591014b1773d59abca8fba5be34df618
Author: Eric Botcazou <ebotcazou@adacore.com>
Date:   Wed Jun 9 12:37:47 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. Do not warn on pointer assignment and
            initialization for storage order purposes if the RHS is a call
            to a DECL_IS_MALLOC function.
    gcc/testsuite/
            * gcc.dg/sso-14.c: New test.

Diff:
---
 gcc/c/c-typeck.c              | 14 ++++++++++-
 gcc/testsuite/gcc.dg/sso-14.c | 56 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 69 insertions(+), 1 deletion(-)

diff --git a/gcc/c/c-typeck.c b/gcc/c/c-typeck.c
index 51a62c800f7..917e670ddd7 100644
--- a/gcc/c/c-typeck.c
+++ b/gcc/c/c-typeck.c
@@ -7294,23 +7294,35 @@ convert_for_assignment (location_t location, location_t expr_loc, tree type,
 	  && (AGGREGATE_TYPE_P (ttl) && TYPE_REVERSE_STORAGE_ORDER (ttl))
 	     != (AGGREGATE_TYPE_P (ttr) && TYPE_REVERSE_STORAGE_ORDER (ttr)))
 	{
+	  tree t;
+
 	  switch (errtype)
 	  {
 	  case ic_argpass:
 	    /* 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);
 	    break;
 	  case ic_assign:
+	    /* Do not warn if the RHS is a call to a function that returns a
+	       pointer that is not an alias.  */
+	    if (TREE_CODE (rhs) != CALL_EXPR
+		|| (t = get_callee_fndecl (rhs)) == NULL_TREE
+		|| !DECL_IS_MALLOC (t))
 	    warning_at (location, OPT_Wscalar_storage_order,
 			"assignment to %qT from pointer type %qT with "
 			"incompatible scalar storage order", type, rhstype);
 	    break;
 	  case ic_init:
+	    /* Do not warn if the RHS is a call to a function that returns a
+	       pointer that is not an alias.  */
+	    if (TREE_CODE (rhs) != CALL_EXPR
+		|| (t = get_callee_fndecl (rhs)) == NULL_TREE
+		|| !DECL_IS_MALLOC (t))
 	    warning_at (location, OPT_Wscalar_storage_order,
 			"initialization of %qT from pointer type %qT with "
 			"incompatible scalar storage order", type, rhstype);
diff --git a/gcc/testsuite/gcc.dg/sso-14.c b/gcc/testsuite/gcc.dg/sso-14.c
new file mode 100644
index 00000000000..8941946c3ab
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/sso-14.c
@@ -0,0 +1,56 @@
+/* PR c/100920 */
+/* Testcase by George Thopas <george.thopas@gmail.com> */
+
+/* { dg-do compile } */
+
+#include <stddef.h>
+#include <stdlib.h>
+#include <string.h>
+
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+#define REV_ENDIANNESS __attribute__((scalar_storage_order("big-endian")))
+#else
+#define REV_ENDIANNESS __attribute__((scalar_storage_order("little-endian")))
+#endif
+
+struct s_1 {
+    int val;
+} REV_ENDIANNESS;
+
+typedef struct s_1 t_1;
+
+struct s_2 {
+    char val;
+} REV_ENDIANNESS;
+
+typedef struct s_2 t_2;
+
+struct s12 {
+    t_1 a[1];
+    t_2 b[1]; 
+} REV_ENDIANNESS;
+
+typedef struct s12 t_s12;
+
+union u12 {
+    t_1 a[1];
+    t_2 b[1];
+} REV_ENDIANNESS;
+
+typedef union u12 t_u12;
+
+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));
+
+  memset (msg1, 0, sizeof (t_s12));
+  memcpy (msg2, &msg1, sizeof (t_s12));
+  same = memcmp (msg1, msg2, sizeof (t_s12));
+
+  return 0;
+}