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libast: Use POSIX_SPAWN_SETSID in spawnveg when needed (#439)

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This commit implements support for POSIX_SPAWN_SETSID in
spawnveg(3). The fork/vfork fallback for spawnveg already attempts
to use setsid in the manner described by the man page, so the
posix_spawn implementation should also do so.

src/lib/libast/comp/spawnveg.c:
- Add support for POSIX_SPAWN_SETSID to the posix_spawn version of
  spawnveg.
- Minor extra: Remove dead code that's never used (the
  _lib_posix_spawn < 2 code block is inside of _lib_posix_spawn >
  1, plus when it's manually enabled by changing the previous #if
  condition you'll find it causes many regression test failures (at
  least on OpenBSD)).

src/lib/libast/man/spawnveg.3:
- Document that spawnveg cannot make the new process a session
  leader if the operating system doesn't support POSIX_SPAWN_SETSID
  and the new process was created using posix_spawn.
This commit is contained in:
Johnothan King 2022-01-27 22:58:01 -08:00 committed by Martijn Dekker
parent 7259153f1a
commit bd9faa81bf
2 changed files with 19 additions and 14 deletions
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22
src/lib/libast/comp/spawnveg.c
View file

@ -47,20 +47,27 @@ NoN(spawnveg)
pid_t pid_t
spawnveg(const char* path, char* const argv[], char* const envv[], pid_t pgid) spawnveg(const char* path, char* const argv[], char* const envv[], pid_t pgid)
{ {
int err; int err, flags = 0;
pid_t pid; pid_t pid;
posix_spawnattr_t attr; posix_spawnattr_t attr;
if (err = posix_spawnattr_init(&attr)) if (err = posix_spawnattr_init(&attr))
goto nope; goto nope;
#if POSIX_SPAWN_SETSID
if (pgid == -1)
flags |= POSIX_SPAWN_SETSID;
else
#endif
if (pgid) if (pgid)
flags |= POSIX_SPAWN_SETPGROUP;
if (flags && (err = posix_spawnattr_setflags(&attr, flags)))
goto bad;
if (pgid && pgid != -1)
{ {
if (pgid <= 1) if (pgid <= 1)
pgid = 0; pgid = 0;
if (err = posix_spawnattr_setpgroup(&attr, pgid)) if (err = posix_spawnattr_setpgroup(&attr, pgid))
goto bad; goto bad;
if (err = posix_spawnattr_setflags(&attr, POSIX_SPAWN_SETPGROUP))
goto bad;
} }
if (err = posix_spawn(&pid, path, NiL, &attr, argv, envv ? envv : environ)) if (err = posix_spawn(&pid, path, NiL, &attr, argv, envv ? envv : environ))
{ {
@ -68,15 +75,6 @@ spawnveg(const char* path, char* const argv[], char* const envv[], pid_t pgid)
goto bad; goto bad;
} }
posix_spawnattr_destroy(&attr); posix_spawnattr_destroy(&attr);
#if _lib_posix_spawn < 2
if (waitpid(pid, &err, WNOHANG|WNOWAIT) == pid && EXIT_STATUS(err) == 127)
{
while (waitpid(pid, NiL, 0) == -1 && errno == EINTR);
if (!access(path, X_OK))
errno = ENOEXEC;
pid = -1;
}
#endif
return pid; return pid;
bad: bad:
posix_spawnattr_destroy(&attr); posix_spawnattr_destroy(&attr);

11
src/lib/libast/man/spawnveg.3
View file

@ -68,7 +68,7 @@ are as in
.L pgid .L pgid
controls the new process group and session: controls the new process group and session:
.TP .TP
.L <0 .L -1
The new process becomes a session leader. The new process becomes a session leader.
It is called in the child context. It is called in the child context.
.TP .TP
@ -86,5 +86,12 @@ The
.L spawnveg .L spawnveg
function cannot set the terminal process group. function cannot set the terminal process group.
As a result, it is incompatible with job control when used with terminals. As a result, it is incompatible with job control when used with terminals.
Additionally, if the
.L POSIX_SPAWN_SETSID
attribute is not supported, then
.L spawnveg
cannot make the new process a session leader when using the
.I posix_spawn
API.
.SH "SEE ALSO" .SH "SEE ALSO"
fork(2), exec(2), setpgid(2), setsid(2), spawnve(2) fork(2), posix_spawn(3), exec(2), setpgid(2), setsid(2), spawnve(2)