When run_command was asked to run a non-existant command,
its behavior varied depending on the platform:
- on POSIX systems, we would fork, and then after the
execvp call failed, we could call die(), which prints a
message to stderr and exits with code 128.
- on Windows, we do a PATH lookup, realize the program
isn't there, and then return ERR_RUN_COMMAND_FORK
The goal of this patch is to make it clear to callers that
the specific error was a missing command. To do this, we
will return the error code ERR_RUN_COMMAND_EXEC, which is
already defined in run-command.h, checked for in several
places, but never actually gets set.
The new behavior is:
- on POSIX systems, we exit the forked process with code
127 (the same as the shell uses to report missing
commands). The parent process recognizes this code and
returns an EXEC error. The stderr message is silenced,
since the caller may be speculatively trying to run a
command. Instead, we use trace_printf so that somebody
interested in debugging can see the error that occured.
- on Windows, we check errno, which is already set
correctly by mingw_spawnvpe, and report an EXEC error
instead of a FORK error
Thus it is safe to speculatively run a command:
int r = run_command_v_opt(argv, 0);
if (r == -ERR_RUN_COMMAND_EXEC)
/* oops, it wasn't found; try something else */
else
/* we failed for some other reason, error is in r */
Signed-off-by: Jeff King <peff@xxxxxxxx>
---
Incorporates JSixt's fix to retain errno across system calls.
run-command.c | 18 ++++++++++++++----
1 files changed, 14 insertions(+), 4 deletions(-)
diff --git a/run-command.c b/run-command.c
index db9ce59..b05c734 100644
--- a/run-command.c
+++ b/run-command.c
@@ -118,7 +118,9 @@ int start_command(struct child_process *cmd)
} else {
execvp(cmd->argv[0], (char *const*) cmd->argv);
}
- die("exec %s failed.", cmd->argv[0]);
+ trace_printf("trace: exec '%s' failed: %s\n", cmd->argv[0],
+ strerror(errno));
+ exit(127);
}
#else
int s0 = -1, s1 = -1, s2 = -1; /* backups of stdin, stdout, stderr */
@@ -187,6 +189,7 @@ int start_command(struct child_process *cmd)
#endif
if (cmd->pid < 0) {
+ int err = errno;
if (need_in)
close_pair(fdin);
else if (cmd->in)
@@ -197,7 +200,9 @@ int start_command(struct child_process *cmd)
close(cmd->out);
if (need_err)
close_pair(fderr);
- return -ERR_RUN_COMMAND_FORK;
+ return err == ENOENT ?
+ -ERR_RUN_COMMAND_EXEC :
+ -ERR_RUN_COMMAND_FORK;
}
if (need_in)
@@ -236,9 +241,14 @@ static int wait_or_whine(pid_t pid)
if (!WIFEXITED(status))
return -ERR_RUN_COMMAND_WAITPID_NOEXIT;
code = WEXITSTATUS(status);
- if (code)
+ switch (code) {
+ case 127:
+ return -ERR_RUN_COMMAND_EXEC;
+ case 0:
+ return 0;
+ default:
return -code;
- return 0;
+ }
}
}
--
1.6.1.1.367.g30b36
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