/* Waiting for a subprocess to finish.
Copyright (C) 2001-2003, 2005-2012 Free Software Foundation, Inc.
Written by Bruno Haible <haible@clisp.cons.org>, 2001.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#include <config.h>
/* Specification. */
#include "wait-process.h"
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/wait.h>
#include "error.h"
#include "fatal-signal.h"
#include "xalloc.h"
#include "gettext.h"
#define _(str) gettext (str)
#define SIZEOF(a) (sizeof(a) / sizeof(a[0]))
#if defined _MSC_VER || defined __MINGW32__
#define WIN32_LEAN_AND_MEAN
#include <windows.h>
/* The return value of spawnvp() is really a process handle as returned
by CreateProcess(). Therefore we can kill it using TerminateProcess. */
#define kill(pid,sig) TerminateProcess ((HANDLE) (pid), sig)
#endif
/* Type of an entry in the slaves array.
The 'used' bit determines whether this entry is currently in use.
(If pid_t was an atomic type like sig_atomic_t, we could just set the
'child' field to 0 when unregistering a slave process, and wouldn't need
the 'used' field.)
The 'used' and 'child' fields are accessed from within the cleanup_slaves()
action, therefore we mark them as 'volatile'. */
typedef struct
{
volatile sig_atomic_t used;
volatile pid_t child;
}
slaves_entry_t;
/* The registered slave subprocesses. */
static slaves_entry_t static_slaves[32];
static slaves_entry_t * volatile slaves = static_slaves;
static sig_atomic_t volatile slaves_count = 0;
static size_t slaves_allocated = SIZEOF (static_slaves);
/* The termination signal for slave subprocesses.
2003-10-07: Terminator becomes Governator. */
#ifdef SIGHUP
# define TERMINATOR SIGHUP
#else
# define TERMINATOR SIGTERM
#endif
/* The cleanup action. It gets called asynchronously. */
static void
cleanup_slaves (void)
{
for (;;)
{
/* Get the last registered slave. */
size_t n = slaves_count;
if (n == 0)
break;
n--;
slaves_count = n;
/* Skip unused entries in the slaves array. */
if (slaves[n].used)
{
pid_t slave = slaves[n].child;
/* Kill the slave. */
kill (slave, TERMINATOR);
}
}
}
/* Register a subprocess as being a slave process. This means that the
subprocess will be terminated when its creator receives a catchable fatal
signal or exits normally. Registration ends when wait_subprocess()
notices that the subprocess has exited. */
void
register_slave_subprocess (pid_t child)
{
static bool cleanup_slaves_registered = false;
if (!cleanup_slaves_registered)
{
atexit (cleanup_slaves);
at_fatal_signal (cleanup_slaves);
cleanup_slaves_registered = true;
}
/* Try to store the new slave in an unused entry of the slaves array. */
{
slaves_entry_t *s = slaves;
slaves_entry_t *s_end = s + slaves_count;
for (; s < s_end; s++)
if (!s->used)
{
/* The two uses of 'volatile' in the slaves_entry_t type above
(and ISO C 99 section 5.1.2.3.(5)) ensure that we mark the
entry as used only after the child pid has been written to the
memory location s->child. */
s->child = child;
s->used = 1;
return;
}
}
if (slaves_count == slaves_allocated)
{
/* Extend the slaves array. Note that we cannot use xrealloc(),
because then the cleanup_slaves() function could access an already
deallocated array. */
slaves_entry_t *old_slaves = slaves;
size_t new_slaves_allocated = 2 * slaves_allocated;
slaves_entry_t *new_slaves =
(slaves_entry_t *)
malloc (new_slaves_allocated * sizeof (slaves_entry_t));
if (new_slaves == NULL)
{
/* xalloc_die() will call exit() which will invoke cleanup_slaves().
Additionally we need to kill child, because it's not yet among
the slaves list. */
kill (child, TERMINATOR);
xalloc_die ();
}
memcpy (new_slaves, old_slaves,
slaves_allocated * sizeof (slaves_entry_t));
slaves = new_slaves;
slaves_allocated = new_slaves_allocated;
/* Now we can free the old slaves array. */
if (old_slaves != static_slaves)
free (old_slaves);
}
/* The three uses of 'volatile' in the types above (and ISO C 99 section
5.1.2.3.(5)) ensure that we increment the slaves_count only after the
new slave and its 'used' bit have been written to the memory locations
that make up slaves[slaves_count]. */
slaves[slaves_count].child = child;
slaves[slaves_count].used = 1;
slaves_count++;
}
/* Unregister a child from the list of slave subprocesses. */
static void
unregister_slave_subprocess (pid_t child)
{
/* The easiest way to remove an entry from a list that can be used by
an asynchronous signal handler is just to mark it as unused. For this,
we rely on sig_atomic_t. */
slaves_entry_t *s = slaves;
slaves_entry_t *s_end = s + slaves_count;
for (; s < s_end; s++)
if (s->used && s->child == child)
s->used = 0;
}
/* Wait for a subprocess to finish. Return its exit code.
If it didn't terminate correctly, exit if exit_on_error is true, otherwise
return 127. */
int
wait_subprocess (pid_t child, const char *progname,
bool ignore_sigpipe, bool null_stderr,
bool slave_process, bool exit_on_error,
int *termsigp)
{
#if HAVE_WAITID && defined WNOWAIT && 0
/* Commented out because waitid() without WEXITED and with WNOWAIT doesn't
work: On Solaris 7 and OSF/1 4.0, it returns -1 and sets errno = ECHILD,
and on HP-UX 10.20 it just hangs. */
/* Use of waitid() with WNOWAIT avoids a race condition: If slave_process is
true, and this process sleeps a very long time between the return from
waitpid() and the execution of unregister_slave_subprocess(), and
meanwhile another process acquires the same PID as child, and then - still
before unregister_slave_subprocess() - this process gets a fatal signal,
it would kill the other totally unrelated process. */
siginfo_t info;
if (termsigp != NULL)
*termsigp = 0;
for (;;)
{
if (waitid (P_PID, child, &info, WEXITED | (slave_process ? WNOWAIT : 0))
< 0)
{
# ifdef EINTR
if (errno == EINTR)
continue;
# endif
if (exit_on_error || !null_stderr)
error (exit_on_error ? EXIT_FAILURE : 0, errno,
_("%s subprocess"), progname);
return 127;
}
/* info.si_code is set to one of CLD_EXITED, CLD_KILLED, CLD_DUMPED,
CLD_TRAPPED, CLD_STOPPED, CLD_CONTINUED. Loop until the program
terminates. */
if (info.si_code == CLD_EXITED
|| info.si_code == CLD_KILLED || info.si_code == CLD_DUMPED)
break;
}
/* The child process has exited or was signalled. */
if (slave_process)
{
/* Unregister the child from the list of slave subprocesses, so that
later, when we exit, we don't kill a totally unrelated process which
may have acquired the same pid. */
unregister_slave_subprocess (child);
/* Now remove the zombie from the process list. */
for (;;)
{
if (waitid (P_PID, child, &info, WEXITED) < 0)
{
# ifdef EINTR
if (errno == EINTR)
continue;
# endif
if (exit_on_error || !null_stderr)
error (exit_on_error ? EXIT_FAILURE : 0, errno,
_("%s subprocess"), progname);
return 127;
}
break;
}
}
switch (info.si_code)
{
case CLD_KILLED:
case CLD_DUMPED:
if (termsigp != NULL)
*termsigp = info.si_status; /* TODO: or info.si_signo? */
# ifdef SIGPIPE
if (info.si_status == SIGPIPE && ignore_sigpipe)
return 0;
# endif
if (exit_on_error || (!null_stderr && termsigp == NULL))
error (exit_on_error ? EXIT_FAILURE : 0, 0,
_("%s subprocess got fatal signal %d"),
progname, info.si_status);
return 127;
case CLD_EXITED:
if (info.si_status == 127)
{
if (exit_on_error || !null_stderr)
error (exit_on_error ? EXIT_FAILURE : 0, 0,
_("%s subprocess failed"), progname);
return 127;
}
return info.si_status;
default:
abort ();
}
#else
/* waitpid() is just as portable as wait() nowadays. */
int status;
if (termsigp != NULL)
*termsigp = 0;
status = 0;
for (;;)
{
int result = waitpid (child, &status, 0);
if (result != child)
{
# ifdef EINTR
if (errno == EINTR)
continue;
# endif
# if 0 /* defined ECHILD */
if (errno == ECHILD)
{
/* Child process nonexistent?! Assume it terminated
successfully. */
status = 0;
break;
}
# endif
if (exit_on_error || !null_stderr)
error (exit_on_error ? EXIT_FAILURE : 0, errno,
_("%s subprocess"), progname);
return 127;
}
/* One of WIFSIGNALED (status), WIFEXITED (status), WIFSTOPPED (status)
must always be true, since we did not specify WCONTINUED in the
waitpid() call. Loop until the program terminates. */
if (!WIFSTOPPED (status))
break;
}
/* The child process has exited or was signalled. */
if (slave_process)
/* Unregister the child from the list of slave subprocesses, so that
later, when we exit, we don't kill a totally unrelated process which
may have acquired the same pid. */
unregister_slave_subprocess (child);
if (WIFSIGNALED (status))
{
if (termsigp != NULL)
*termsigp = WTERMSIG (status);
# ifdef SIGPIPE
if (WTERMSIG (status) == SIGPIPE && ignore_sigpipe)
return 0;
# endif
if (exit_on_error || (!null_stderr && termsigp == NULL))
error (exit_on_error ? EXIT_FAILURE : 0, 0,
_("%s subprocess got fatal signal %d"),
progname, (int) WTERMSIG (status));
return 127;
}
if (!WIFEXITED (status))
abort ();
if (WEXITSTATUS (status) == 127)
{
if (exit_on_error || !null_stderr)
error (exit_on_error ? EXIT_FAILURE : 0, 0,
_("%s subprocess failed"), progname);
return 127;
}
return WEXITSTATUS (status);
#endif
}