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posix_spawn on AIX
|
From: |
Bruno Haible |
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Subject: |
posix_spawn on AIX |
|
Date: |
Thu, 2 Oct 2008 01:26:30 +0200 |
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User-agent: |
KMail/1.5.4 |
Hi,
posix_spawn exists on AIX 5.3 and 6.1, but it is unusable. Rainer Tammer
identified two bugs:
- failure to execute any program in the child process, when the parent
program uses POSIX threads.
- when the child process fails to execute the given program, it outputs
the stdio buffers before calling _exit(127). The parent later flushes
its stdio buffers as well. So in the end the buffered contents is
output twice.
I'm committing this:
2008-10-01 Bruno Haible <address@hidden>
Avoid the broken posix_spawn function on AIX 5.3 and 6.1.
* m4/posix_spawn.m4 (gl_POSIX_SPAWN_WORKS): New macro.
(gl_POSIX_SPAWN_BODY): Invoke it. Set REPLACE_POSIX_SPAWN if needed.
* doc/posix-functions/posix_spawn.texi: Mention the AIX bugs.
* doc/posix-functions/posix_spawnp.texi: Likewise.
* m4/execute.m4 (gl_EXECUTE): Invoke gl_POSIX_SPAWN_WORKS, to check
whether posix_spawn actually works.
* m4/pipe.m4 (gl_PIPE): Likewise.
* modules/execute (Files): Add m4/posix_spawn.m4.
* modules/pipe (Files): Add m4/posix_spawn.m4.
Reported and analyzed by Rainer Tammer <address@hidden>.
*** m4/posix_spawn.m4.orig 2008-10-02 01:13:30.000000000 +0200
--- m4/posix_spawn.m4 2008-10-01 13:45:50.000000000 +0200
***************
*** 1,4 ****
! # posix_spawn.m4 serial 1
dnl Copyright (C) 2008 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
--- 1,4 ----
! # posix_spawn.m4 serial 2
dnl Copyright (C) 2008 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
***************
*** 36,50 ****
dnl AC_CHECK_FUNCS_ONCE([posix_spawnattr_getsigmask])
dnl AC_CHECK_FUNCS_ONCE([posix_spawnattr_setsigmask])
dnl AC_CHECK_FUNCS_ONCE([posix_spawnattr_destroy])
! if test $ac_cv_func_posix_spawn != yes; then
HAVE_POSIX_SPAWN=0
- dnl For now, assume that if posix_spawn exists, it also works.
- if false; then
- REPLACE_POSIX_SPAWN=1
- fi
fi
])
AC_DEFUN([gl_POSIX_SPAWN_INTERNAL],
[
AC_LIBOBJ([spawni])
--- 36,214 ----
dnl AC_CHECK_FUNCS_ONCE([posix_spawnattr_getsigmask])
dnl AC_CHECK_FUNCS_ONCE([posix_spawnattr_setsigmask])
dnl AC_CHECK_FUNCS_ONCE([posix_spawnattr_destroy])
! if test $ac_cv_func_posix_spawn = yes; then
! gl_POSIX_SPAWN_WORKS
! case "$gl_cv_func_posix_spawn_works" in
! *yes) ;;
! *) REPLACE_POSIX_SPAWN=1 ;;
! esac
! else
HAVE_POSIX_SPAWN=0
fi
])
+ dnl Test whether posix_spawn actually works.
+ dnl posix_spawn on AIX 5.3..6.1 has a bug: When it fails to execute the
+ dnl program, the child process exits with exit() rather than _exit(),
+ dnl which causes the stdio buffers to be flushed. Reported by Rainer Tammer.
+ dnl posix_spawn on AIX 5.3..6.1 has also a second bug: It does not work
+ dnl when POSIX threads are used. But we don't test against this bug here.
+ AC_DEFUN([gl_POSIX_SPAWN_WORKS],
+ [
+ AC_REQUIRE([AC_PROG_CC])
+ AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
+ AC_CACHE_CHECK([whether posix_spawn works], [gl_cv_func_posix_spawn_works],
+ [if test $cross_compiling = no; then
+ AC_LINK_IFELSE([AC_LANG_PROGRAM([[
+ #include <errno.h>
+ #include <fcntl.h>
+ #include <signal.h>
+ #include <spawn.h>
+ #include <stdbool.h>
+ #include <stdio.h>
+ #include <stdlib.h>
+ #include <string.h>
+ #include <unistd.h>
+ #include <sys/types.h>
+ #include <sys/wait.h>
+
+ extern char **environ;
+
+ #ifndef STDIN_FILENO
+ # define STDIN_FILENO 0
+ #endif
+ #ifndef STDOUT_FILENO
+ # define STDOUT_FILENO 1
+ #endif
+ #ifndef STDERR_FILENO
+ # define STDERR_FILENO 2
+ #endif
+
+ #ifndef WTERMSIG
+ # define WTERMSIG(x) ((x) & 0x7f)
+ #endif
+ #ifndef WCOREDUMP
+ # define WCOREDUMP(x) ((x) & 0x80)
+ #endif
+ #ifndef WEXITSTATUS
+ # define WEXITSTATUS(x) (((x) >> 8) & 0xff)
+ #endif
+ #ifndef WIFSIGNALED
+ # define WIFSIGNALED(x) (WTERMSIG (x) != 0 && WTERMSIG(x) != 0x7f)
+ #endif
+ #ifndef WIFEXITED
+ # define WIFEXITED(x) (WTERMSIG (x) == 0)
+ #endif
+ #ifndef WIFSTOPPED
+ # define WIFSTOPPED(x) (WTERMSIG (x) == 0x7f)
+ #endif
+
+ #define CHILD_PROGRAM_FILENAME "/non/exist/ent"
+
+ static int
+ fd_safer (int fd)
+ {
+ if (0 <= fd && fd <= 2)
+ {
+ int f = fd_safer (dup (fd));
+ int e = errno;
+ close (fd);
+ errno = e;
+ fd = f;
+ }
+
+ return fd;
+ }
+ ]],
+ dnl Now comes the main() function.
+ [[
+ char *argv[2] = { CHILD_PROGRAM_FILENAME, NULL };
+ int ofd[2];
+ sigset_t blocked_signals;
+ sigset_t fatal_signal_set;
+ posix_spawn_file_actions_t actions;
+ bool actions_allocated;
+ posix_spawnattr_t attrs;
+ bool attrs_allocated;
+ int err;
+ pid_t child;
+ int status;
+ int exitstatus;
+
+ setvbuf (stdout, NULL, _IOFBF, 0);
+ puts ("This should be seen only once.");
+ if (pipe (ofd) < 0 || (ofd[1] = fd_safer (ofd[1])) < 0)
+ {
+ perror ("cannot create pipe");
+ exit (1);
+ }
+ sigprocmask (SIG_SETMASK, NULL, &blocked_signals);
+ sigemptyset (&fatal_signal_set);
+ sigaddset (&fatal_signal_set, SIGINT);
+ sigaddset (&fatal_signal_set, SIGTERM);
+ sigaddset (&fatal_signal_set, SIGHUP);
+ sigaddset (&fatal_signal_set, SIGPIPE);
+ sigprocmask (SIG_BLOCK, &fatal_signal_set, NULL);
+ actions_allocated = false;
+ attrs_allocated = false;
+ if ((err = posix_spawn_file_actions_init (&actions)) != 0
+ || (actions_allocated = true,
+ (err = posix_spawn_file_actions_adddup2 (&actions, ofd[0],
STDIN_FILENO)) != 0
+ || (err = posix_spawn_file_actions_addclose (&actions, ofd[0])) != 0
+ || (err = posix_spawn_file_actions_addclose (&actions, ofd[1])) != 0
+ || (err = posix_spawnattr_init (&attrs)) != 0
+ || (attrs_allocated = true,
+ (err = posix_spawnattr_setsigmask (&attrs, &blocked_signals))
!= 0
+ || (err = posix_spawnattr_setflags (&attrs,
POSIX_SPAWN_SETSIGMASK)) != 0)
+ || (err = posix_spawnp (&child, CHILD_PROGRAM_FILENAME, &actions,
&attrs, argv, environ)) != 0))
+ {
+ if (actions_allocated)
+ posix_spawn_file_actions_destroy (&actions);
+ if (attrs_allocated)
+ posix_spawnattr_destroy (&attrs);
+ sigprocmask (SIG_UNBLOCK, &fatal_signal_set, NULL);
+ errno = err;
+ perror ("subprocess failed");
+ exit (1);
+ }
+ posix_spawn_file_actions_destroy (&actions);
+ posix_spawnattr_destroy (&attrs);
+ sigprocmask (SIG_UNBLOCK, &fatal_signal_set, NULL);
+ close (ofd[0]);
+ close (ofd[1]);
+ status = 0;
+ while (waitpid (child, &status, 0) != child)
+ ;
+ if (!WIFEXITED (status))
+ {
+ fprintf (stderr, "subprocess terminated with unexpected wait status
%d\n", status);
+ exit (1);
+ }
+ exitstatus = WEXITSTATUS (status);
+ if (exitstatus != 127)
+ {
+ fprintf (stderr, "subprocess terminated with unexpected exit status
%d\n", exitstatus);
+ exit (1);
+ }
+ ]])],
+ [if test -s conftest$ac_exeext \
+ && ./conftest$ac_exeext > conftest.out \
+ && echo 'This should be seen only once.' > conftest.ok \
+ && cmp conftest.out conftest.ok > /dev/null; then
+ gl_cv_func_posix_spawn_works=yes
+ else
+ gl_cv_func_posix_spawn_works=no
+ fi],
+ [gl_cv_func_posix_spawn_works=no])
+ else
+ case "$host_os" in
+ aix*) gl_cv_func_posix_spawn_works="guessing no";;
+ *) gl_cv_func_posix_spawn_works="guessing yes";;
+ esac
+ fi
+ ])
+ ])
+
AC_DEFUN([gl_POSIX_SPAWN_INTERNAL],
[
AC_LIBOBJ([spawni])
*** doc/posix-functions/posix_spawn.texi.orig 2008-10-02 01:13:30.000000000
+0200
--- doc/posix-functions/posix_spawn.texi 2008-10-02 01:10:24.000000000
+0200
***************
*** 11,21 ****
@item
This function is missing on some platforms:
MacOS X 10.3, FreeBSD 6.0, NetBSD 3.0, OpenBSD 3.8, AIX 5.1, HP-UX 11, IRIX
6.5, OSF/1 5.1, Solaris 9, Cygwin, mingw, Interix 3.5, BeOS.
@end itemize
Portability problems not fixed by Gnulib:
@itemize
@item
This function does not work on some platforms:
! mingw.
@end itemize
--- 11,25 ----
@item
This function is missing on some platforms:
MacOS X 10.3, FreeBSD 6.0, NetBSD 3.0, OpenBSD 3.8, AIX 5.1, HP-UX 11, IRIX
6.5, OSF/1 5.1, Solaris 9, Cygwin, mingw, Interix 3.5, BeOS.
+ @item
+ When this function fails, it causes the stdio buffer contents to be output
+ twice on some platforms:
+ AIX 6.1.
@end itemize
Portability problems not fixed by Gnulib:
@itemize
@item
This function does not work on some platforms:
! AIX 6.1 (under particular circumstances), mingw.
@end itemize
*** doc/posix-functions/posix_spawnp.texi.orig 2008-10-02 01:13:30.000000000
+0200
--- doc/posix-functions/posix_spawnp.texi 2008-10-02 01:10:25.000000000
+0200
***************
*** 11,21 ****
@item
This function is missing on some platforms:
MacOS X 10.3, FreeBSD 6.0, NetBSD 3.0, OpenBSD 3.8, AIX 5.1, HP-UX 11, IRIX
6.5, OSF/1 5.1, Solaris 9, Cygwin, mingw, Interix 3.5, BeOS.
@end itemize
Portability problems not fixed by Gnulib:
@itemize
@item
This function does not work on some platforms:
! mingw.
@end itemize
--- 11,25 ----
@item
This function is missing on some platforms:
MacOS X 10.3, FreeBSD 6.0, NetBSD 3.0, OpenBSD 3.8, AIX 5.1, HP-UX 11, IRIX
6.5, OSF/1 5.1, Solaris 9, Cygwin, mingw, Interix 3.5, BeOS.
+ @item
+ When this function fails, it causes the stdio buffer contents to be output
+ twice on some platforms:
+ AIX 6.1.
@end itemize
Portability problems not fixed by Gnulib:
@itemize
@item
This function does not work on some platforms:
! AIX 6.1 (under particular circumstances), mingw.
@end itemize
*** m4/execute.m4.orig 2008-10-02 01:13:30.000000000 +0200
--- m4/execute.m4 2008-10-01 13:44:57.000000000 +0200
***************
*** 1,5 ****
! # execute.m4 serial 1
! dnl Copyright (C) 2003 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
dnl with or without modifications, as long as this notice is preserved.
--- 1,5 ----
! # execute.m4 serial 2
! dnl Copyright (C) 2003, 2008 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
dnl with or without modifications, as long as this notice is preserved.
***************
*** 11,15 ****
AC_REQUIRE([AC_TYPE_MODE_T])
AC_CHECK_HEADERS_ONCE(unistd.h)
AC_REQUIRE([AC_FUNC_FORK])
! AC_CHECK_FUNCS(posix_spawn)
])
--- 11,23 ----
AC_REQUIRE([AC_TYPE_MODE_T])
AC_CHECK_HEADERS_ONCE(unistd.h)
AC_REQUIRE([AC_FUNC_FORK])
! AC_CHECK_FUNC([posix_spawn],
! [gl_POSIX_SPAWN_WORKS
! case "$gl_cv_func_posix_spawn_works" in
! *yes)
! AC_DEFINE([HAVE_POSIX_SPAWN], 1,
! [Define if you have the posix_spawn() function and it works.])
! ;;
! esac
! ])
])
*** m4/pipe.m4.orig 2008-10-02 01:13:30.000000000 +0200
--- m4/pipe.m4 2008-10-01 13:45:13.000000000 +0200
***************
*** 1,5 ****
! # pipe.m4 serial 1
! dnl Copyright (C) 2004 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
dnl with or without modifications, as long as this notice is preserved.
--- 1,5 ----
! # pipe.m4 serial 2
! dnl Copyright (C) 2004, 2008 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
dnl with or without modifications, as long as this notice is preserved.
***************
*** 12,16 ****
AC_REQUIRE([AC_C_INLINE])
AC_REQUIRE([AC_TYPE_MODE_T])
AC_REQUIRE([AC_FUNC_FORK])
! AC_CHECK_FUNCS(posix_spawn)
])
--- 12,24 ----
AC_REQUIRE([AC_C_INLINE])
AC_REQUIRE([AC_TYPE_MODE_T])
AC_REQUIRE([AC_FUNC_FORK])
! AC_CHECK_FUNC([posix_spawn],
! [gl_POSIX_SPAWN_WORKS
! case "$gl_cv_func_posix_spawn_works" in
! *yes)
! AC_DEFINE([HAVE_POSIX_SPAWN], 1,
! [Define if you have the posix_spawn() function and it works.])
! ;;
! esac
! ])
])
*** modules/execute.orig 2008-10-02 01:13:30.000000000 +0200
--- modules/execute 2008-10-01 13:45:40.000000000 +0200
***************
*** 6,11 ****
--- 6,12 ----
lib/execute.c
lib/w32spawn.h
m4/execute.m4
+ m4/posix_spawn.m4
Depends-on:
error
*** modules/pipe.orig 2008-10-02 01:13:30.000000000 +0200
--- modules/pipe 2008-10-01 13:45:44.000000000 +0200
***************
*** 6,11 ****
--- 6,12 ----
lib/pipe.c
lib/w32spawn.h
m4/pipe.m4
+ m4/posix_spawn.m4
Depends-on:
environ
- posix_spawn on AIX,
Bruno Haible <=