Return requested size for malloc_usable_size when MALLOC_CHECK_ > 0

[BZ #1349]

malloc_usable_size returns the usable size in an allocated chunk,
which may be >= the requested size. In the case of MALLOC_CHECK_ being
exported to > 0 however, only the requested size is usable, since a
magic value is written at the end of the request size to trap writes
beyond request bounds. Hence, when MALLOC_CHECK_ is exported to > 0,
malloc_usable_size() should return the request size.

1 files changed, 49 insertions, 0 deletions

diff --git a/malloc/tst-malloc-usable.c b/malloc/tst-malloc-usable.c
new file mode 100644
index 0000000..18decd8
--- /dev/null
+++ b/malloc/tst-malloc-usable.c
@@ -0,0 +1,49 @@
+/* Ensure that malloc_usable_size returns the request size with
+   MALLOC_CHECK_ exported to a positive value.
+
+   Copyright (C) 2012 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <malloc.h>
+#include <string.h>
+#include <stdio.h>
+
+static int
+do_test (void)
+{
+  size_t usable_size;
+  void *p = malloc (7);
+  if (!p)
+    {
+      printf ("memory allocation failed\n");
+      return 1;
+    }
+
+  usable_size = malloc_usable_size (p);
+  if (usable_size != 7)
+    {
+      printf ("malloc_usable_size: expected 7 but got %zu\n", usable_size);
+      return 1;
+    }
+
+  memset (p, 0, usable_size);
+  free (p);
+  return 0;
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"