stdlib/test-bz22786: Avoid spurious test failures using alias mappings

On systems without enough random-access memory, stdlib/test-bz22786
will go deeply into swap and time out, even with a substantial
TIMEOUTFACTOR.  This commit adds a facility to construct repeating
strings with alias mappings, so that the requirement for physical
memory, and uses it in stdlib/test-bz22786.

(cherry picked from commit f5e7e95921847bd83186bfe621fc2b48c4de5477)

1 files changed, 6 insertions, 10 deletions

diff --git a/stdlib/test-bz22786.c b/stdlib/test-bz22786.c
index 777bf9180f..bb1e04f2de 100644
--- a/stdlib/test-bz22786.c
+++ b/stdlib/test-bz22786.c
@@ -26,6 +26,7 @@
 #include <unistd.h>
 #include <sys/stat.h>
 #include <sys/types.h>
+#include <support/blob_repeat.h>
 #include <support/check.h>
 #include <support/support.h>
 #include <support/temp_file.h>
@@ -39,17 +40,12 @@ do_test (void)
   const char *lnk = xasprintf ("%s/symlink", dir);
   const size_t path_len = (size_t) INT_MAX + strlen (lnk) + 1;
 
-  DIAG_PUSH_NEEDS_COMMENT;
-#if __GNUC_PREREQ (7, 0)
-  /* GCC 7 warns about too-large allocations; here we need such
-     allocation to succeed for the test to work.  */
-  DIAG_IGNORE_NEEDS_COMMENT (7, "-Walloc-size-larger-than=");
-#endif
-  char *path = malloc (path_len);
-  DIAG_POP_NEEDS_COMMENT;
+  struct support_blob_repeat repeat
+    = support_blob_repeat_allocate ("a", 1, path_len);
+  char *path = repeat.start;
   if (path == NULL)
     {
-      printf ("malloc (%zu): %m\n", path_len);
+      printf ("Repeated allocation (%zu bytes): %m\n", path_len);
       /* On 31-bit s390 the malloc will always fail as we do not have
 	 so much memory, and we want to mark the test unsupported.
 	 Likewise on systems with little physical memory the test will
@@ -62,7 +58,6 @@ do_test (void)
   /* Construct very long path = "/tmp/bz22786.XXXX/symlink/aaaa....."  */
   char *p = mempcpy (path, lnk, strlen (lnk));
   *(p++) = '/';
-  memset (p, 'a', path_len - (p - path) - 2);
   p[path_len - (p - path) - 1] = '\0';
 
   /* This call crashes before the fix for bz22786 on 32-bit platforms.  */
@@ -76,6 +71,7 @@ do_test (void)
 
   /* Cleanup.  */
   unlink (lnk);
+  support_blob_repeat_free (&repeat);
 
   return 0;
 }