This patch improves the default posix implementation of posix_spawn{p}
and align with Linux one. The main idea is to fix some issues already
fixed in Linux code, and deprecated vfork internal usage (source of
various bug reports). In a short:
- It moves POSIX_SPAWN_USEVFORK usage and sets it a no-op. Since
the process that actually spawn the new process do not share
memory with parent (with vfork), it fixes BZ#14750 for this
implementation.
- It uses a pipe to correctly obtain the return upon failure
of execution (BZ#18433).
- It correctly enable/disable asynchronous cancellation (checked
on ptl/tst-exec5.c).
- It correctly disable/enable signal handling.
Using this version instead of Linux shows only one regression,
posix/tst-spawn3, because of pipe2 usage which increase total
number of file descriptor.
* sysdeps/posix/spawni.c (__spawni_child): New function.
(__spawni): Rename to __spawnix.
ccfb296472