[vlc-devel] [PATCH 5/6] spawn: provide fallback implementation using fork() & exec()

[Alexandre Janniaux]

On Mon, Sep 21, 2020 at 06:52:25AM +0200, Steve Lhomme wrote:
> This broke the tvOS build
> https://code.videolan.org/videolan/vlc/-/jobs/450328

Sorry, I was pretty sure it was Ok for iOS (though not
shippable, but it can be fixed after since it's not a
build breakage) but completely forgot about tvOS that
doesn't even expose the primitives.

Regards,
--
Alexandre Janniaux
Videolabs

>
> On 2020-09-19 12:29, Rémi Denis-Courmont wrote:
> > ---
> >   src/posix/spawn.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++-
> >   1 file changed, 64 insertions(+), 1 deletion(-)
> >
> > diff --git a/src/posix/spawn.c b/src/posix/spawn.c
> > index 774c6cb6cb..233bb01047 100644
> > --- a/src/posix/spawn.c
> > +++ b/src/posix/spawn.c
> > @@ -115,11 +115,74 @@ out:
> >   #else /* _POSIX_SPAWN */
> > +#include <vlc_fs.h>
> > +
> >   static int vlc_spawn_inner(pid_t *restrict pid, const char *path,
> >                              const int *fdv, const char *const *argv,
> >                              bool search)
> >   {
> > -    (void) pid; (void) path; (void) fdv; (void) argv; (void) search;
> > +    size_t argc = 0;
> > +
> > +    assert(pid != NULL);
> > +    assert(path != NULL);
> > +    assert(fdv != NULL);
> > +    assert(argv != NULL);
> > +
> > +    int nulfd = vlc_open("/dev/null", O_RDWR);
> > +    if (unlikely(nulfd == -1))
> > +        return errno;
> > +
> > +    while (argv[argc++] != NULL);
> > +
> > +    char **vargv = malloc(sizeof (*argv) * argc);
> > +    if (unlikely(vargv == NULL)) {
> > +        vlc_close(nulfd);
> > +        return errno;
> > +    }
> > +
> > +    for (size_t i = 0; i < argc; i++)
> > +        vargv[i] = (char *)argv[i];
> > +
> > +    *pid = fork();
> > +
> > +    switch (*pid) {
> > +         case -1:
> > +             return errno;
> > +
> > +         case 0:
> > +             break;
> > +
> > +         default:
> > +             free(vargv);
> > +             vlc_close(nulfd);
> > +             return 0;
> > +    }
> > +
> > +    for (int newfd = 0; newfd < 3 || fdv[newfd] != -1; newfd++) {
> > +        int oldfd = fdv[newfd];
> > +
> > +        if (oldfd == -1)
> > +            oldfd = nulfd;
> > +
> > +        if (oldfd == newfd)
> > +            fcntl(oldfd, F_SETFD, fcntl(oldfd, F_GETFD) & ~FD_CLOEXEC);
> > +        else
> > +        if (dup2(oldfd, newfd) < 0)
> > +            _exit(1);
> > +    }
> > +
> > +    sigset_t set;
> > +
> > +    sigemptyset(&set);
> > +    pthread_sigmask(SIG_SETMASK, &set, NULL);
> > +    signal(SIGPIPE, SIG_DFL);
> > +
> > +    if (search)
> > +        execvp(path, vargv);
> > +    else
> > +        execv(path, vargv);
> > +
> > +    _exit(1);
> >   }
> >   #endif /* _POSIX_SPAWN */
> > --
> > 2.28.0
> >
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