Oh, and posix_spawn_file_actions_init() should return errno, not -1, if malloc(3) fails.
On Fri, Mar 9, 2012 at 10:54 AM, Matthew Dempsky <matt...@dempsky.org> wrote: > On Thu, Mar 8, 2012 at 1:24 PM, Frank Denis <a...@me.com> wrote: >> See http://download.pureftpd.org/misc/OpenBSD/patches/posix_spawn.diff > > Hi Frank, > > I briefly looked over this code, and the diff looks good to me except > for one subtle FreeBSDism: memory writes done in a vfork(2)'d child > process will not affect the parent process. This is critical for how > FreeBSD's posix_spawn() propagates errors from the spawned child > process. > > I haven't tested this, but I suspect if (e.g.) you try to > posix_spawn() a non-existent program, that posix_spawn() will still > return a successful return value. > > Instead of using a volatile int on the stack, you'll need to allocate > some extra memory using mmap and MAP_SHARED. E.g., see the sample > program below. > > If you can fix that, I think it's good to commit. Some regress tests > would be good too though. (However, I'll be offline until March 18 > though, so someone else will need to actually commit it.) > > Thanks! > > > $ ./beep > error=42 > > $ cat beep.c > #include <sys/mman.h> > #include <unistd.h> > #include <stdio.h> > #include <err.h> > > int main() > { > void *mem; > volatile int *errorp; > > mem = mmap(0, sizeof(*errorp), PROT_READ|PROT_WRITE, > MAP_SHARED|MAP_ANON, -1, 0); > if (mem == MAP_FAILED) err(100, "mmap"); > errorp = mem; > *errorp = 0; > > switch (vfork()) { > case -1: err(100, "vfork\n"); return 0; break; > case 0: *errorp = 42; return 0; break; > } > > printf("error=%d\n", *errorp); > if (munmap(mem, sizeof(*errorp)) == -1) err(100, "munmap"); > return 0; > }
