[PATCH v3 5/5] avoid -Wuse-after-free [BZ #26779]

[Joseph Myers]

Note that there are still -Wuse-after-free build failures in the testsuite 
for many 32-bit platforms.  E.g., on i686-linux-gnu:

tst-mallocalign1.c: In function 'do_test':
tst-mallocalign1.c:69:1: error: pointer 'p' used after 'free' [-Werror=use-after-free]
   69 | }
      | ^
tst-mallocalign1.c:42:3: note: call to 'free' here
   42 |   free (p);
      |   ^~~~~~~~

Also, the s390x-linux-gnu-O3 build-many-glibcs.py configuration shows 
failures:

In function 'do_test',
    inlined from 'legacy_test_function' at ../test-skeleton.c:55:10:
tst-realloc.c:134:12: error: pointer 'p' may be used after 'realloc' [-Werror=use-after-free]
  134 |       if (c[i] != 0xff)
      |           ~^~~
tst-realloc.c:124:7: note: call to 'realloc' here
  124 |   c = realloc (p, -1);
      |       ^~~~~~~~~~~~~~~
tst-realloc.c:134:12: error: pointer 'p' may be used after 'realloc' [-Werror=use-after-free]
  134 |       if (c[i] != 0xff)
      |           ~^~~
tst-realloc.c:124:7: note: call to 'realloc' here
  124 |   c = realloc (p, -1);
      |       ^~~~~~~~~~~~~~~
tst-realloc.c:134:12: error: pointer 'p' may be used after 'realloc' [-Werror=use-after-free]
  134 |       if (c[i] != 0xff)
      |           ~^~~
tst-realloc.c:124:7: note: call to 'realloc' here
  124 |   c = realloc (p, -1);
      |       ^~~~~~~~~~~~~~~
tst-realloc.c:134:12: error: pointer 'p' may be used after 'realloc' [-Werror=use-after-free]
  134 |       if (c[i] != 0xff)
      |           ~^~~
tst-realloc.c:124:7: note: call to 'realloc' here
  124 |   c = realloc (p, -1);
      |       ^~~~~~~~~~~~~~~
tst-realloc.c:134:12: error: pointer 'p' may be used after 'realloc' [-Werror=use-after-free]
  134 |       if (c[i] != 0xff)
      |           ~^~~
tst-realloc.c:124:7: note: call to 'realloc' here
  124 |   c = realloc (p, -1);
      |       ^~~~~~~~~~~~~~~
tst-realloc.c:134:12: error: pointer 'p' may be used after 'realloc' [-Werror=use-after-free]
  134 |       if (c[i] != 0xff)
      |           ~^~~
tst-realloc.c:124:7: note: call to 'realloc' here
  124 |   c = realloc (p, -1);
      |       ^~~~~~~~~~~~~~~
tst-realloc.c:134:12: error: pointer 'p' may be used after 'realloc' [-Werror=use-after-free]
  134 |       if (c[i] != 0xff)
      |           ~^~~
tst-realloc.c:124:7: note: call to 'realloc' here
  124 |   c = realloc (p, -1);
      |       ^~~~~~~~~~~~~~~
tst-realloc.c:134:12: error: pointer 'p' may be used after 'realloc' [-Werror=use-after-free]
  134 |       if (c[i] != 0xff)
      |           ~^~~
tst-realloc.c:124:7: note: call to 'realloc' here
  124 |   c = realloc (p, -1);
      |       ^~~~~~~~~~~~~~~
tst-realloc.c:134:12: error: pointer 'p' may be used after 'realloc' [-Werror=use-after-free]
  134 |       if (c[i] != 0xff)
      |           ~^~~
tst-realloc.c:124:7: note: call to 'realloc' here
  124 |   c = realloc (p, -1);
      |       ^~~~~~~~~~~~~~~
tst-realloc.c:134:12: error: pointer 'p' may be used after 'realloc' [-Werror=use-after-free]
  134 |       if (c[i] != 0xff)
      |           ~^~~
tst-realloc.c:124:7: note: call to 'realloc' here
  124 |   c = realloc (p, -1);
      |       ^~~~~~~~~~~~~~~
tst-realloc.c:134:12: error: pointer 'p' may be used after 'realloc' [-Werror=use-after-free]
  134 |       if (c[i] != 0xff)
      |           ~^~~
tst-realloc.c:124:7: note: call to 'realloc' here
  124 |   c = realloc (p, -1);
      |       ^~~~~~~~~~~~~~~
tst-realloc.c:134:12: error: pointer 'p' may be used after 'realloc' [-Werror=use-after-free]
  134 |       if (c[i] != 0xff)
      |           ~^~~
tst-realloc.c:124:7: note: call to 'realloc' here
  124 |   c = realloc (p, -1);
      |       ^~~~~~~~~~~~~~~
tst-realloc.c:134:12: error: pointer 'p' may be used after 'realloc' [-Werror=use-after-free]
  134 |       if (c[i] != 0xff)
      |           ~^~~
tst-realloc.c:124:7: note: call to 'realloc' here
  124 |   c = realloc (p, -1);
      |       ^~~~~~~~~~~~~~~
tst-realloc.c:134:12: error: pointer 'p' may be used after 'realloc' [-Werror=use-after-free]
  134 |       if (c[i] != 0xff)
      |           ~^~~
tst-realloc.c:124:7: note: call to 'realloc' here
  124 |   c = realloc (p, -1);
      |       ^~~~~~~~~~~~~~~
tst-realloc.c:134:12: error: pointer 'p' may be used after 'realloc' [-Werror=use-after-free]
  134 |       if (c[i] != 0xff)
      |           ~^~~
tst-realloc.c:124:7: note: call to 'realloc' here
  124 |   c = realloc (p, -1);
      |       ^~~~~~~~~~~~~~~

-- 
Joseph S. Myers
joseph@codesourcery.com