summaryrefslogtreecommitdiff
path: root/run-command.c
blob: c8029f239405e463bba5b033a7321faf16ca6c0d (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
#include "cache.h"
#include "run-command.h"
#include "exec_cmd.h"
#include "sigchain.h"
#include "argv-array.h"

void child_process_init(struct child_process *child)
{
	memset(child, 0, sizeof(*child));
	argv_array_init(&child->args);
	argv_array_init(&child->env_array);
}

struct child_to_clean {
	pid_t pid;
	struct child_to_clean *next;
};
static struct child_to_clean *children_to_clean;
static int installed_child_cleanup_handler;

static void cleanup_children(int sig)
{
	while (children_to_clean) {
		struct child_to_clean *p = children_to_clean;
		children_to_clean = p->next;
		kill(p->pid, sig);
		free(p);
	}
}

static void cleanup_children_on_signal(int sig)
{
	cleanup_children(sig);
	sigchain_pop(sig);
	raise(sig);
}

static void cleanup_children_on_exit(void)
{
	cleanup_children(SIGTERM);
}

static void mark_child_for_cleanup(pid_t pid)
{
	struct child_to_clean *p = xmalloc(sizeof(*p));
	p->pid = pid;
	p->next = children_to_clean;
	children_to_clean = p;

	if (!installed_child_cleanup_handler) {
		atexit(cleanup_children_on_exit);
		sigchain_push_common(cleanup_children_on_signal);
		installed_child_cleanup_handler = 1;
	}
}

static void clear_child_for_cleanup(pid_t pid)
{
	struct child_to_clean **pp;

	for (pp = &children_to_clean; *pp; pp = &(*pp)->next) {
		struct child_to_clean *clean_me = *pp;

		if (clean_me->pid == pid) {
			*pp = clean_me->next;
			free(clean_me);
			return;
		}
	}
}

static inline void close_pair(int fd[2])
{
	close(fd[0]);
	close(fd[1]);
}

#ifndef GIT_WINDOWS_NATIVE
static inline void dup_devnull(int to)
{
	int fd = open("/dev/null", O_RDWR);
	if (fd < 0)
		die_errno(_("open /dev/null failed"));
	if (dup2(fd, to) < 0)
		die_errno(_("dup2(%d,%d) failed"), fd, to);
	close(fd);
}
#endif

static char *locate_in_PATH(const char *file)
{
	const char *p = getenv("PATH");
	struct strbuf buf = STRBUF_INIT;

	if (!p || !*p)
		return NULL;

	while (1) {
		const char *end = strchrnul(p, ':');

		strbuf_reset(&buf);

		/* POSIX specifies an empty entry as the current directory. */
		if (end != p) {
			strbuf_add(&buf, p, end - p);
			strbuf_addch(&buf, '/');
		}
		strbuf_addstr(&buf, file);

		if (!access(buf.buf, F_OK))
			return strbuf_detach(&buf, NULL);

		if (!*end)
			break;
		p = end + 1;
	}

	strbuf_release(&buf);
	return NULL;
}

static int exists_in_PATH(const char *file)
{
	char *r = locate_in_PATH(file);
	free(r);
	return r != NULL;
}

int sane_execvp(const char *file, char * const argv[])
{
	if (!execvp(file, argv))
		return 0; /* cannot happen ;-) */

	/*
	 * When a command can't be found because one of the directories
	 * listed in $PATH is unsearchable, execvp reports EACCES, but
	 * careful usability testing (read: analysis of occasional bug
	 * reports) reveals that "No such file or directory" is more
	 * intuitive.
	 *
	 * We avoid commands with "/", because execvp will not do $PATH
	 * lookups in that case.
	 *
	 * The reassignment of EACCES to errno looks like a no-op below,
	 * but we need to protect against exists_in_PATH overwriting errno.
	 */
	if (errno == EACCES && !strchr(file, '/'))
		errno = exists_in_PATH(file) ? EACCES : ENOENT;
	else if (errno == ENOTDIR && !strchr(file, '/'))
		errno = ENOENT;
	return -1;
}

static const char **prepare_shell_cmd(const char **argv)
{
	int argc, nargc = 0;
	const char **nargv;

	for (argc = 0; argv[argc]; argc++)
		; /* just counting */
	/* +1 for NULL, +3 for "sh -c" plus extra $0 */
	nargv = xmalloc(sizeof(*nargv) * (argc + 1 + 3));

	if (argc < 1)
		die("BUG: shell command is empty");

	if (strcspn(argv[0], "|&;<>()$`\\\"' \t\n*?[#~=%") != strlen(argv[0])) {
#ifndef GIT_WINDOWS_NATIVE
		nargv[nargc++] = SHELL_PATH;
#else
		nargv[nargc++] = "sh";
#endif
		nargv[nargc++] = "-c";

		if (argc < 2)
			nargv[nargc++] = argv[0];
		else {
			struct strbuf arg0 = STRBUF_INIT;
			strbuf_addf(&arg0, "%s \"$@\"", argv[0]);
			nargv[nargc++] = strbuf_detach(&arg0, NULL);
		}
	}

	for (argc = 0; argv[argc]; argc++)
		nargv[nargc++] = argv[argc];
	nargv[nargc] = NULL;

	return nargv;
}

#ifndef GIT_WINDOWS_NATIVE
static int execv_shell_cmd(const char **argv)
{
	const char **nargv = prepare_shell_cmd(argv);
	trace_argv_printf(nargv, "trace: exec:");
	sane_execvp(nargv[0], (char **)nargv);
	free(nargv);
	return -1;
}
#endif

#ifndef GIT_WINDOWS_NATIVE
static int child_notifier = -1;

static void notify_parent(void)
{
	/*
	 * execvp failed.  If possible, we'd like to let start_command
	 * know, so failures like ENOENT can be handled right away; but
	 * otherwise, finish_command will still report the error.
	 */
	xwrite(child_notifier, "", 1);
}
#endif

static inline void set_cloexec(int fd)
{
	int flags = fcntl(fd, F_GETFD);
	if (flags >= 0)
		fcntl(fd, F_SETFD, flags | FD_CLOEXEC);
}

static int wait_or_whine(pid_t pid, const char *argv0)
{
	int status, code = -1;
	pid_t waiting;
	int failed_errno = 0;

	while ((waiting = waitpid(pid, &status, 0)) < 0 && errno == EINTR)
		;	/* nothing */

	if (waiting < 0) {
		failed_errno = errno;
		error("waitpid for %s failed: %s", argv0, strerror(errno));
	} else if (waiting != pid) {
		error("waitpid is confused (%s)", argv0);
	} else if (WIFSIGNALED(status)) {
		code = WTERMSIG(status);
		if (code != SIGINT && code != SIGQUIT)
			error("%s died of signal %d", argv0, code);
		/*
		 * This return value is chosen so that code & 0xff
		 * mimics the exit code that a POSIX shell would report for
		 * a program that died from this signal.
		 */
		code += 128;
	} else if (WIFEXITED(status)) {
		code = WEXITSTATUS(status);
		/*
		 * Convert special exit code when execvp failed.
		 */
		if (code == 127) {
			code = -1;
			failed_errno = ENOENT;
		}
	} else {
		error("waitpid is confused (%s)", argv0);
	}

	clear_child_for_cleanup(pid);

	errno = failed_errno;
	return code;
}

int start_command(struct child_process *cmd)
{
	int need_in, need_out, need_err;
	int fdin[2], fdout[2], fderr[2];
	int failed_errno;
	char *str;

	if (!cmd->argv)
		cmd->argv = cmd->args.argv;
	if (!cmd->env)
		cmd->env = cmd->env_array.argv;

	/*
	 * In case of errors we must keep the promise to close FDs
	 * that have been passed in via ->in and ->out.
	 */

	need_in = !cmd->no_stdin && cmd->in < 0;
	if (need_in) {
		if (pipe(fdin) < 0) {
			failed_errno = errno;
			if (cmd->out > 0)
				close(cmd->out);
			str = "standard input";
			goto fail_pipe;
		}
		cmd->in = fdin[1];
	}

	need_out = !cmd->no_stdout
		&& !cmd->stdout_to_stderr
		&& cmd->out < 0;
	if (need_out) {
		if (pipe(fdout) < 0) {
			failed_errno = errno;
			if (need_in)
				close_pair(fdin);
			else if (cmd->in)
				close(cmd->in);
			str = "standard output";
			goto fail_pipe;
		}
		cmd->out = fdout[0];
	}

	need_err = !cmd->no_stderr && cmd->err < 0;
	if (need_err) {
		if (pipe(fderr) < 0) {
			failed_errno = errno;
			if (need_in)
				close_pair(fdin);
			else if (cmd->in)
				close(cmd->in);
			if (need_out)
				close_pair(fdout);
			else if (cmd->out)
				close(cmd->out);
			str = "standard error";
fail_pipe:
			error("cannot create %s pipe for %s: %s",
				str, cmd->argv[0], strerror(failed_errno));
			argv_array_clear(&cmd->args);
			argv_array_clear(&cmd->env_array);
			errno = failed_errno;
			return -1;
		}
		cmd->err = fderr[0];
	}

	trace_argv_printf(cmd->argv, "trace: run_command:");
	fflush(NULL);

#ifndef GIT_WINDOWS_NATIVE
{
	int notify_pipe[2];
	if (pipe(notify_pipe))
		notify_pipe[0] = notify_pipe[1] = -1;

	cmd->pid = fork();
	failed_errno = errno;
	if (!cmd->pid) {
		/*
		 * Redirect the channel to write syscall error messages to
		 * before redirecting the process's stderr so that all die()
		 * in subsequent call paths use the parent's stderr.
		 */
		if (cmd->no_stderr || need_err) {
			int child_err = dup(2);
			set_cloexec(child_err);
			set_error_handle(fdopen(child_err, "w"));
		}

		close(notify_pipe[0]);
		set_cloexec(notify_pipe[1]);
		child_notifier = notify_pipe[1];
		atexit(notify_parent);

		if (cmd->no_stdin)
			dup_devnull(0);
		else if (need_in) {
			dup2(fdin[0], 0);
			close_pair(fdin);
		} else if (cmd->in) {
			dup2(cmd->in, 0);
			close(cmd->in);
		}

		if (cmd->no_stderr)
			dup_devnull(2);
		else if (need_err) {
			dup2(fderr[1], 2);
			close_pair(fderr);
		} else if (cmd->err > 1) {
			dup2(cmd->err, 2);
			close(cmd->err);
		}

		if (cmd->no_stdout)
			dup_devnull(1);
		else if (cmd->stdout_to_stderr)
			dup2(2, 1);
		else if (need_out) {
			dup2(fdout[1], 1);
			close_pair(fdout);
		} else if (cmd->out > 1) {
			dup2(cmd->out, 1);
			close(cmd->out);
		}

		if (cmd->dir && chdir(cmd->dir))
			die_errno("exec '%s': cd to '%s' failed", cmd->argv[0],
			    cmd->dir);
		if (cmd->env) {
			for (; *cmd->env; cmd->env++) {
				if (strchr(*cmd->env, '='))
					putenv((char *)*cmd->env);
				else
					unsetenv(*cmd->env);
			}
		}
		if (cmd->git_cmd)
			execv_git_cmd(cmd->argv);
		else if (cmd->use_shell)
			execv_shell_cmd(cmd->argv);
		else
			sane_execvp(cmd->argv[0], (char *const*) cmd->argv);
		if (errno == ENOENT) {
			if (!cmd->silent_exec_failure)
				error("cannot run %s: %s", cmd->argv[0],
					strerror(ENOENT));
			exit(127);
		} else {
			die_errno("cannot exec '%s'", cmd->argv[0]);
		}
	}
	if (cmd->pid < 0)
		error("cannot fork() for %s: %s", cmd->argv[0],
			strerror(errno));
	else if (cmd->clean_on_exit)
		mark_child_for_cleanup(cmd->pid);

	/*
	 * Wait for child's execvp. If the execvp succeeds (or if fork()
	 * failed), EOF is seen immediately by the parent. Otherwise, the
	 * child process sends a single byte.
	 * Note that use of this infrastructure is completely advisory,
	 * therefore, we keep error checks minimal.
	 */
	close(notify_pipe[1]);
	if (read(notify_pipe[0], &notify_pipe[1], 1) == 1) {
		/*
		 * At this point we know that fork() succeeded, but execvp()
		 * failed. Errors have been reported to our stderr.
		 */
		wait_or_whine(cmd->pid, cmd->argv[0]);
		failed_errno = errno;
		cmd->pid = -1;
	}
	close(notify_pipe[0]);
}
#else
{
	int fhin = 0, fhout = 1, fherr = 2;
	const char **sargv = cmd->argv;

	if (cmd->no_stdin)
		fhin = open("/dev/null", O_RDWR);
	else if (need_in)
		fhin = dup(fdin[0]);
	else if (cmd->in)
		fhin = dup(cmd->in);

	if (cmd->no_stderr)
		fherr = open("/dev/null", O_RDWR);
	else if (need_err)
		fherr = dup(fderr[1]);
	else if (cmd->err > 2)
		fherr = dup(cmd->err);

	if (cmd->no_stdout)
		fhout = open("/dev/null", O_RDWR);
	else if (cmd->stdout_to_stderr)
		fhout = dup(fherr);
	else if (need_out)
		fhout = dup(fdout[1]);
	else if (cmd->out > 1)
		fhout = dup(cmd->out);

	if (cmd->git_cmd)
		cmd->argv = prepare_git_cmd(cmd->argv);
	else if (cmd->use_shell)
		cmd->argv = prepare_shell_cmd(cmd->argv);

	cmd->pid = mingw_spawnvpe(cmd->argv[0], cmd->argv, (char**) cmd->env,
			cmd->dir, fhin, fhout, fherr);
	failed_errno = errno;
	if (cmd->pid < 0 && (!cmd->silent_exec_failure || errno != ENOENT))
		error("cannot spawn %s: %s", cmd->argv[0], strerror(errno));
	if (cmd->clean_on_exit && cmd->pid >= 0)
		mark_child_for_cleanup(cmd->pid);

	if (cmd->git_cmd)
		free(cmd->argv);

	cmd->argv = sargv;
	if (fhin != 0)
		close(fhin);
	if (fhout != 1)
		close(fhout);
	if (fherr != 2)
		close(fherr);
}
#endif

	if (cmd->pid < 0) {
		if (need_in)
			close_pair(fdin);
		else if (cmd->in)
			close(cmd->in);
		if (need_out)
			close_pair(fdout);
		else if (cmd->out)
			close(cmd->out);
		if (need_err)
			close_pair(fderr);
		else if (cmd->err)
			close(cmd->err);
		argv_array_clear(&cmd->args);
		argv_array_clear(&cmd->env_array);
		errno = failed_errno;
		return -1;
	}

	if (need_in)
		close(fdin[0]);
	else if (cmd->in)
		close(cmd->in);

	if (need_out)
		close(fdout[1]);
	else if (cmd->out)
		close(cmd->out);

	if (need_err)
		close(fderr[1]);
	else if (cmd->err)
		close(cmd->err);

	return 0;
}

int finish_command(struct child_process *cmd)
{
	int ret = wait_or_whine(cmd->pid, cmd->argv[0]);
	argv_array_clear(&cmd->args);
	argv_array_clear(&cmd->env_array);
	return ret;
}

int run_command(struct child_process *cmd)
{
	int code;

	if (cmd->out < 0 || cmd->err < 0)
		die("BUG: run_command with a pipe can cause deadlock");

	code = start_command(cmd);
	if (code)
		return code;
	return finish_command(cmd);
}

int run_command_v_opt(const char **argv, int opt)
{
	return run_command_v_opt_cd_env(argv, opt, NULL, NULL);
}

int run_command_v_opt_cd_env(const char **argv, int opt, const char *dir, const char *const *env)
{
	struct child_process cmd = CHILD_PROCESS_INIT;
	cmd.argv = argv;
	cmd.no_stdin = opt & RUN_COMMAND_NO_STDIN ? 1 : 0;
	cmd.git_cmd = opt & RUN_GIT_CMD ? 1 : 0;
	cmd.stdout_to_stderr = opt & RUN_COMMAND_STDOUT_TO_STDERR ? 1 : 0;
	cmd.silent_exec_failure = opt & RUN_SILENT_EXEC_FAILURE ? 1 : 0;
	cmd.use_shell = opt & RUN_USING_SHELL ? 1 : 0;
	cmd.clean_on_exit = opt & RUN_CLEAN_ON_EXIT ? 1 : 0;
	cmd.dir = dir;
	cmd.env = env;
	return run_command(&cmd);
}

#ifndef NO_PTHREADS
static pthread_t main_thread;
static int main_thread_set;
static pthread_key_t async_key;
static pthread_key_t async_die_counter;

static void *run_thread(void *data)
{
	struct async *async = data;
	intptr_t ret;

	pthread_setspecific(async_key, async);
	ret = async->proc(async->proc_in, async->proc_out, async->data);
	return (void *)ret;
}

static NORETURN void die_async(const char *err, va_list params)
{
	vreportf("fatal: ", err, params);

	if (in_async()) {
		struct async *async = pthread_getspecific(async_key);
		if (async->proc_in >= 0)
			close(async->proc_in);
		if (async->proc_out >= 0)
			close(async->proc_out);
		pthread_exit((void *)128);
	}

	exit(128);
}

static int async_die_is_recursing(void)
{
	void *ret = pthread_getspecific(async_die_counter);
	pthread_setspecific(async_die_counter, (void *)1);
	return ret != NULL;
}

int in_async(void)
{
	if (!main_thread_set)
		return 0; /* no asyncs started yet */
	return !pthread_equal(main_thread, pthread_self());
}

#else

static struct {
	void (**handlers)(void);
	size_t nr;
	size_t alloc;
} git_atexit_hdlrs;

static int git_atexit_installed;

static void git_atexit_dispatch(void)
{
	size_t i;

	for (i=git_atexit_hdlrs.nr ; i ; i--)
		git_atexit_hdlrs.handlers[i-1]();
}

static void git_atexit_clear(void)
{
	free(git_atexit_hdlrs.handlers);
	memset(&git_atexit_hdlrs, 0, sizeof(git_atexit_hdlrs));
	git_atexit_installed = 0;
}

#undef atexit
int git_atexit(void (*handler)(void))
{
	ALLOC_GROW(git_atexit_hdlrs.handlers, git_atexit_hdlrs.nr + 1, git_atexit_hdlrs.alloc);
	git_atexit_hdlrs.handlers[git_atexit_hdlrs.nr++] = handler;
	if (!git_atexit_installed) {
		if (atexit(&git_atexit_dispatch))
			return -1;
		git_atexit_installed = 1;
	}
	return 0;
}
#define atexit git_atexit

static int process_is_async;
int in_async(void)
{
	return process_is_async;
}

#endif

int start_async(struct async *async)
{
	int need_in, need_out;
	int fdin[2], fdout[2];
	int proc_in, proc_out;

	need_in = async->in < 0;
	if (need_in) {
		if (pipe(fdin) < 0) {
			if (async->out > 0)
				close(async->out);
			return error("cannot create pipe: %s", strerror(errno));
		}
		async->in = fdin[1];
	}

	need_out = async->out < 0;
	if (need_out) {
		if (pipe(fdout) < 0) {
			if (need_in)
				close_pair(fdin);
			else if (async->in)
				close(async->in);
			return error("cannot create pipe: %s", strerror(errno));
		}
		async->out = fdout[0];
	}

	if (need_in)
		proc_in = fdin[0];
	else if (async->in)
		proc_in = async->in;
	else
		proc_in = -1;

	if (need_out)
		proc_out = fdout[1];
	else if (async->out)
		proc_out = async->out;
	else
		proc_out = -1;

#ifdef NO_PTHREADS
	/* Flush stdio before fork() to avoid cloning buffers */
	fflush(NULL);

	async->pid = fork();
	if (async->pid < 0) {
		error("fork (async) failed: %s", strerror(errno));
		goto error;
	}
	if (!async->pid) {
		if (need_in)
			close(fdin[1]);
		if (need_out)
			close(fdout[0]);
		git_atexit_clear();
		process_is_async = 1;
		exit(!!async->proc(proc_in, proc_out, async->data));
	}

	mark_child_for_cleanup(async->pid);

	if (need_in)
		close(fdin[0]);
	else if (async->in)
		close(async->in);

	if (need_out)
		close(fdout[1]);
	else if (async->out)
		close(async->out);
#else
	if (!main_thread_set) {
		/*
		 * We assume that the first time that start_async is called
		 * it is from the main thread.
		 */
		main_thread_set = 1;
		main_thread = pthread_self();
		pthread_key_create(&async_key, NULL);
		pthread_key_create(&async_die_counter, NULL);
		set_die_routine(die_async);
		set_die_is_recursing_routine(async_die_is_recursing);
	}

	if (proc_in >= 0)
		set_cloexec(proc_in);
	if (proc_out >= 0)
		set_cloexec(proc_out);
	async->proc_in = proc_in;
	async->proc_out = proc_out;
	{
		int err = pthread_create(&async->tid, NULL, run_thread, async);
		if (err) {
			error("cannot create thread: %s", strerror(err));
			goto error;
		}
	}
#endif
	return 0;

error:
	if (need_in)
		close_pair(fdin);
	else if (async->in)
		close(async->in);

	if (need_out)
		close_pair(fdout);
	else if (async->out)
		close(async->out);
	return -1;
}

int finish_async(struct async *async)
{
#ifdef NO_PTHREADS
	return wait_or_whine(async->pid, "child process");
#else
	void *ret = (void *)(intptr_t)(-1);

	if (pthread_join(async->tid, &ret))
		error("pthread_join failed");
	return (int)(intptr_t)ret;
#endif
}

const char *find_hook(const char *name)
{
	static struct strbuf path = STRBUF_INIT;

	strbuf_reset(&path);
	strbuf_git_path(&path, "hooks/%s", name);
	if (access(path.buf, X_OK) < 0)
		return NULL;
	return path.buf;
}

int run_hook_ve(const char *const *env, const char *name, va_list args)
{
	struct child_process hook = CHILD_PROCESS_INIT;
	const char *p;

	p = find_hook(name);
	if (!p)
		return 0;

	argv_array_push(&hook.args, p);
	while ((p = va_arg(args, const char *)))
		argv_array_push(&hook.args, p);
	hook.env = env;
	hook.no_stdin = 1;
	hook.stdout_to_stderr = 1;

	return run_command(&hook);
}

int run_hook_le(const char *const *env, const char *name, ...)
{
	va_list args;
	int ret;

	va_start(args, name);
	ret = run_hook_ve(env, name, args);
	va_end(args);

	return ret;
}

int capture_command(struct child_process *cmd, struct strbuf *buf, size_t hint)
{
	cmd->out = -1;
	if (start_command(cmd) < 0)
		return -1;

	if (strbuf_read(buf, cmd->out, hint) < 0) {
		close(cmd->out);
		finish_command(cmd); /* throw away exit code */
		return -1;
	}

	close(cmd->out);
	return finish_command(cmd);
}