[testsuite] Make the Wnonnull independent of system headers.

To avoid the result of this test depending on the implementation of
the system 'string.h', provide prototypes for the two functions used
in the test.

gcc/testsuite/ChangeLog:

2019-10-22  Iain Sandoe  <iain@sandoe.co.uk>

	* gcc.dg/Wnonnull.c: Provide prototypes for strlen and memcpy.
	Use __SIZE_TYPE__ instead of size_t.

From-SVN: r277280

gcc/testsuite/ChangeLog

+2019-10-22  Iain Sandoe  <iain@sandoe.co.uk>
+
+	* gcc.dg/Wnonnull.c: Provide prototypes for strlen and memcpy.
+	Use __SIZE_TYPE__ instead of size_t.
+
 2019-10-21  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	* g++.dg/parse/qualified2.C: Tighten dg-error directive.

gcc/testsuite/gcc.dg/Wnonnull.c

@@ -2,16 +2,10 @@
    { dg-do compile }
    { dg-options "-O2 -Wall" } */
 
-#ifndef __APPLE__
-#include <string.h>
-#else
-/* OSX headers do not mark up the nonnull elements yet.  */
-# include <stddef.h>
-extern size_t strlen (const char *__s)
-		      __attribute ((pure)) __attribute ((nonnull (1)));
+extern __SIZE_TYPE__ strlen (const char *__s)
+			     __attribute ((pure)) __attribute ((nonnull (1)));
 extern void *memcpy (void *__restrict __dest, const void *__restrict __src,
-		     size_t __n) __attribute ((nonnull (1, 2)));
-#endif
+		     __SIZE_TYPE__ __n) __attribute ((nonnull (1, 2)));
 
 char buf[100];
 
@@ -23,9 +17,9 @@ struct Test
 
 __attribute ((nonnull (1, 2)))
 inline char*
-my_strcpy (char *restrict dst, const char *restrict src, size_t size)
+my_strcpy (char *restrict dst, const char *restrict src, __SIZE_TYPE__ size)
 {
-  size_t len = strlen (src);        /* { dg-warning "argument 1 null where non-null expected" } */
+  __SIZE_TYPE__ len = strlen (src); /* { dg-warning "argument 1 null where non-null expected" } */
   if (len < size)
     memcpy (dst, src, len + 1);     /* { dg-warning "argument 2 null where non-null expected" } */
   else