Along with posix_spawn_file_actions_addchdir,
posix_spawn_file_actions_addfchdir is the subject of a change proposal
for POSIX: <http://austingroupbugs.net/view.php?id=1208>
Hide internal __posix_spawn_file_actions_realloc and /__spawni functions
to allow direct access within libc.so and libc.a without using GOT nor
PLT.
[BZ #18822]
* posix/spawn_int.h (__posix_spawn_file_actions_realloc): Add
attribute_hidden.
(__spawni): Likewise.
POSIX requires that we make a copy, so we allocate a new string
and free it in posix_spawn_file_actions_destroy.
Reported by David Reid, Alex Gaynor, and Glyph Lefkowitz. This bug
may have security implications.