Previously, failures during execvp could be detected only by
finish_command. However, in some situations it is beneficial for the
parent process to know earlier that the child process will not run.
The idea to use a pipe to signal failures to the parent process and
the test case were lifted from patches by Ilari Liusvaara.
Signed-off-by: Johannes Sixt <j6t@xxxxxxxx>
---
Makefile | 1 +
run-command.c | 47 ++++++++++++++++++++++++++++++++++++++++++++++-
t/t0061-run-command.sh | 14 ++++++++++++++
test-run-command.c | 35 +++++++++++++++++++++++++++++++++++
4 files changed, 96 insertions(+), 1 deletions(-)
create mode 100755 t/t0061-run-command.sh
create mode 100644 test-run-command.c
diff --git a/Makefile b/Makefile
index 87fc7ff..22c1546 100644
--- a/Makefile
+++ b/Makefile
@@ -1785,6 +1785,7 @@ TEST_PROGRAMS += test-genrandom$X
TEST_PROGRAMS += test-match-trees$X
TEST_PROGRAMS += test-parse-options$X
TEST_PROGRAMS += test-path-utils$X
+TEST_PROGRAMS += test-run-command$X
TEST_PROGRAMS += test-sha1$X
TEST_PROGRAMS += test-sigchain$X
diff --git a/run-command.c b/run-command.c
index dccac37..473b7f8 100644
--- a/run-command.c
+++ b/run-command.c
@@ -17,6 +17,12 @@ static inline void dup_devnull(int to)
#ifndef WIN32
static int child_err = 2;
+static int child_notifier = -1;
+
+static void notify_parent()
+{
+ write(child_notifier, "", 1);
+}
static NORETURN void die_child(const char *err, va_list params)
{
@@ -142,6 +148,11 @@ fail_pipe:
trace_argv_printf(cmd->argv, "trace: run_command:");
#ifndef WIN32
+{
+ int notify_pipe[2];
+ if (pipe(notify_pipe))
+ notify_pipe[0] = notify_pipe[1] = -1;
+
fflush(NULL);
cmd->pid = fork();
if (!cmd->pid) {
@@ -156,6 +167,11 @@ fail_pipe:
}
set_die_routine(die_child);
+ 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) {
@@ -196,8 +212,16 @@ fail_pipe:
unsetenv(*cmd->env);
}
}
- if (cmd->preexec_cb)
+ if (cmd->preexec_cb) {
+ /*
+ * We cannot predict what the pre-exec callback does.
+ * Forgo parent notification.
+ */
+ close(child_notifier);
+ child_notifier = -1;
+
cmd->preexec_cb();
+ }
if (cmd->git_cmd) {
execv_git_cmd(cmd->argv);
} else {
@@ -215,6 +239,27 @@ fail_pipe:
if (cmd->pid < 0)
error("cannot fork() for %s: %s", cmd->argv[0],
strerror(failed_errno = errno));
+
+ /*
+ * 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], ¬ify_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],
+ cmd->silent_exec_failure);
+ failed_errno = errno;
+ cmd->pid = -1;
+ }
+ close(notify_pipe[0]);
+}
#else
{
int s0 = -1, s1 = -1, s2 = -1; /* backups of stdin, stdout, stderr */
diff --git a/t/t0061-run-command.sh b/t/t0061-run-command.sh
new file mode 100755
index 0000000..10b26e4
--- /dev/null
+++ b/t/t0061-run-command.sh
@@ -0,0 +1,14 @@
+#!/bin/sh
+#
+# Copyright (c) 2009 Ilari Liusvaara
+#
+
+test_description='Test run command'
+
+. ./test-lib.sh
+
+test_expect_success 'start_command reports ENOENT' '
+ test-run-command start-command-ENOENT ./does-not-exist
+'
+
+test_done
diff --git a/test-run-command.c b/test-run-command.c
new file mode 100644
index 0000000..a1d5306
--- /dev/null
+++ b/test-run-command.c
@@ -0,0 +1,35 @@
+/*
+ * test-run-command.c: test run command API.
+ *
+ * (C) 2009 Ilari Liusvaara <ilari.liusvaara@xxxxxxxxxxx>
+ *
+ * This code is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include "git-compat-util.h"
+#include "run-command.h"
+#include <string.h>
+#include <errno.h>
+
+int main(int argc, char **argv)
+{
+ struct child_process proc;
+
+ memset(&proc, 0, sizeof(proc));
+
+ if(argc < 3)
+ return 1;
+ proc.argv = (const char **)argv+2;
+
+ if (!strcmp(argv[1], "start-command-ENOENT")) {
+ if (start_command(&proc) < 0 && errno == ENOENT)
+ return 0;
+ fprintf(stderr, "FAIL %s\n", argv[1]);
+ return 1;
+ }
+
+ fprintf(stderr, "check usage\n");
+ return 1;
+}
--
1.6.6.115.gd1ab3
--
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