Re: m4 1.4.14 esyscmd problems on FreeBSD

[Bruno Haible]

Hi Johan,

Thanks for the added details.

> The code actually works fine on FreeBSD 7.2 machines. It's also
> fine on OpenBSD (4.7) and MacOS (Darwin 8.11). So it seems something was
> changed / broken in FreeBSD 8.0.

FreeBSD 8.0 has its own, new implementation of the posix_spawn* functions,
whereas on the other platforms the gnulib replacement is used.

> > This quickly identifies a problem:
> > 
> >   2143 gm4      CALL  sigprocmask(SIG_BLOCK,0x545a20,0)
> >   2143 gm4      RET   sigprocmask 0
> >   2143 gm4      CALL  vfork
> >   2144 gm4      RET   fork 0
> >   2144 gm4      CALL  sched_setscheduler(0,<invalid=0>,0x800a0e918)
> >   2144 gm4      RET   sched_setscheduler -1 errno 1 Operation not permitted
> >   2144 gm4      CALL  exit(0x7f)
> >   2143 gm4      RET   vfork 2144/0x860
> >   2143 gm4      CALL  sigprocmask(SIG_UNBLOCK,0x545a20,0)
> >   2143 gm4      RET   sigprocmask 0

How come that sched_setscheduler is called? The only use of posix_spawn and
posix_spawnp that is made by m4 1.4.14 (see lib/execute.c and lib/pipe.c) is
with a flags value of POSIX_SPAWN_SETSIGMASK. Whereas in the native FreeBSD
posix_spawn[p] (as well as in the gnulib replacement),  sched_setscheduler
is only called if the flags word contains the POSIX_SPAWN_SETSCHEDULER bit.

FreeBSD's POSIX_SPAWN_SETSIGMASK is 0x20, FreeBSD's POSIX_SPAWN_SETSCHEDULER
is 0x08. Whereas the gnulib replacement value for POSIX_SPAWN_SETSIGMASK is
0x08. It seems gnulib's replacement value is in use when it should not. I'm
applying this fix.


2010-03-02  Bruno Haible  <address@hidden>

        spawn: Don't override the system defined values on FreeBSD 8.
        * lib/spawn.in.h (POSIX_SPAWN_RESETIDS, POSIX_SPAWN_SETPGROUP,
        POSIX_SPAWN_SETSIGDEF, POSIX_SPAWN_SETSIGMASK,
        POSIX_SPAWN_SETSCHEDPARAM, POSIX_SPAWN_SETSCHEDULER): Don't redefine
        if HAVE_POSIX_SPAWN is 1.
        Reported by Johan van Selst <address@hidden> via Eric Blake.

*** lib/spawn.in.h.orig Tue Mar  2 11:53:02 2010
--- lib/spawn.in.h      Tue Mar  2 11:48:54 2010
***************
*** 110,126 ****
  
  
  /* Flags to be set in the `posix_spawnattr_t'.  */
! #if @REPLACE_POSIX_SPAWN@
  /* Use the values from the system, for better compatibility.  */
  /* But this implementation does not support AIX extensions.  */
! # undef POSIX_SPAWN_FORK_HANDLERS
! #else
! # define POSIX_SPAWN_RESETIDS           0x01
! # define POSIX_SPAWN_SETPGROUP          0x02
! # define POSIX_SPAWN_SETSIGDEF          0x04
! # define POSIX_SPAWN_SETSIGMASK         0x08
! # define POSIX_SPAWN_SETSCHEDPARAM      0x10
! # define POSIX_SPAWN_SETSCHEDULER       0x20
  #endif
  /* A GNU extension.  Use the next free bit position.  */
  #define POSIX_SPAWN_USEVFORK \
--- 110,128 ----
  
  
  /* Flags to be set in the `posix_spawnattr_t'.  */
! #if address@hidden@
! # if @REPLACE_POSIX_SPAWN@
  /* Use the values from the system, for better compatibility.  */
  /* But this implementation does not support AIX extensions.  */
! #  undef POSIX_SPAWN_FORK_HANDLERS
! # else
! #  define POSIX_SPAWN_RESETIDS           0x01
! #  define POSIX_SPAWN_SETPGROUP          0x02
! #  define POSIX_SPAWN_SETSIGDEF          0x04
! #  define POSIX_SPAWN_SETSIGMASK         0x08
! #  define POSIX_SPAWN_SETSCHEDPARAM      0x10
! #  define POSIX_SPAWN_SETSCHEDULER       0x20
! # endif
  #endif
  /* A GNU extension.  Use the next free bit position.  */
  #define POSIX_SPAWN_USEVFORK \