This is a regression introduced in commit 67a589e505. Previously, the
source/target FD pairs were stored in `needdup_fd_assignments`, in
consecutive entries, so source FDs had even indices and target FDs had
odd indices.
I didn’t notice that the array index was being incremented by 2 when
closing FDs, when porting from the old code. So previously the code was
only closing the source FDs; after the port, it was closing source and
target FDs.
That’s incorrect, as the target FDs are just integers in the parent
process. It’s only in the child process where they are actually FDs —
and `g_subprocess_launcher_close()` is never called in the child
process.
This resulted in some strange misbehaviours in any process which used
`g_subprocess_launcher_take_fd()` with target FDs which could have
possibly aliased with other FDs in the parent process (and which weren’t
equal to their mapped source FDs).
Thanks to Olivier Fourdan for the detailed bug report.
Signed-off-by: Philip Withnall <pwithnall@endlessos.org>
Fixes: #2332
This improves performance by eliminating the use of a
`GSpawnChildSetupFunc` in the common case (since that setup code has now
moved into `g_spawn*()` itself), and enables the use of the fix to avoid
the child error reporting FD being overwritten by target FD mappings,
introduced via `g_spawn_async_with_pipes_and_fds()`.
It reworks how the source/target FD mapping is stored within
`GSubprocessLauncher` to match what `g_spawn*()` uses. The two
approaches are equivalent.
Signed-off-by: Philip Withnall <pwithnall@endlessos.org>
Fixes: #2097
By default, when using g_subprocess_launcher_take_fd() to pass an
FD to a child, the GSubprocessLauncher object also takes ownership
of the FD in the parent, and closes it during finalize(). This is
a reasonable assumption in the majority of the cases, but sometimes
it isn't a good idea.
An example is when creating a GSubprocessLauncher in JavaScript:
here, the destruction process is managed by the Garbage Collector,
which means that those sockets will remain opened for some time
after all the references to the object has been droped. This means
that it could be not possible to detect when the child has closed
that same FD, because in order to make that work, both FDs
instances (the one in the parent and the one in the children) must
be closed. This can be a problem in, as an example, a process that
launches a child that communicates with Wayland using an specific
socket (like when using the new API MetaWaylandClient).
Of course, it isn't a valid solution to manually call close() in
the parent process just after the call to spawn(), because the FD
number could be reused in the time between it is manually closed,
and when the object is destroyed and closes again that FD. If that
happens, it will close an incorrect FD.
One solution could be to call run_dispose() from Javascript on the
GSubprocessLauncher object, to force freeing the resources.
Unfortunately, the current code frees them in the finalize()
method, not in dispose() (this is fixed in !1670 (merged) ) but it
isn't a very elegant solution.
This proposal adds a new method, g_subprocess_launcher_close(),
that allows to close the FDs passed to the child. To avoid problems,
after closing an FD with this method, no more spawns are allowed.
Fix: https://gitlab.gnome.org/GNOME/glib/-/merge_requests/1677
There are a number of nice things this class brings:
0) Has a race-free termination API on all platforms (on UNIX, calls to
kill() and waitpid() are coordinated as not to cause problems).
1) Operates in terms of G{Input,Output}Stream, not file descriptors
2) Standard GIO-style async API for wait() with cancellation
3) Makes some simple cases easy, like synchronously spawning a
process with an argument list
4) Makes hard cases possible, like asynchronously running a process
with stdout/stderr merged, output directly to a file path
Much rewriting and code review from Ryan Lortie <desrt@desrt.ca>
https://bugzilla.gnome.org/show_bug.cgi?id=672102
