Newlib's posix_spawn has been taken from FreeBSD. The code relies on
BSD-specific behaviour of vfork, namely the fact that vfork blocks
the parent until the child exits or calls execve as well as the fact
that the child shares parent memory in non-COW mode.
This behaviour can't be emulated by Cygwin. Cygwin's vfork is
equivalent to fork. This is POSIX-compliant, but it's lacking BSD's
vfork ingrained synchronization of the parent to wait for the child
calling execve, or the chance to just write a variable and the parent
will see the result.
So this requires a Cygwin-specific solution. The core function of
posix_spawn, called do_posix_spawn is now implemented twice, once using
the BSD method, and once for Cygwin using Windows synchronization under
the hood waiting for the child to call execve and signalling errors
upstream. The Windows specifics are hidden inside Cygwin, so newlib
only calls internal Cygwin functions.
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
in newlib or Cygwin.
(process_spawnattr): Use sigprocmask rather than _sigprocmask. Use
sigaction rather than _sigaction.
(process_file_actions_entry): Use dup2 rather than _dup2.
(do_posix_spawn): Use execvpe rather than _execvpe. Use waitpid
rather than _waitpid.
* configure.host: Disable new posix_spawn function for all
users of posix dir except Cygwin.
* libc/posix/Makefile.am: Add support for new posix_spawn function.
* libc/posix/Makefile.in: Regenerate.
* libc/posix/posix_spawn.c: New file.
* libc/include/spawn.h: Ditto.
Corinna Vinschen
Yaakov Selkowitz
Jeff Johnston