start_command: report child process setup errors to the parent's stderr

diff --git a/run-command.c b/run-command.c
index cf2d8f7fae1356e50736cb9d599625df79738a2a..02c7bfba8fb7491b936d819cd54054e645b58ef8 100644 (file)
--- a/run-command.c
+++ b/run-command.c
@@ -15,6 +15,30 @@ static inline void dup_devnull(int to)
        close(fd);
 }
 
+#ifndef WIN32
+static int child_err = 2;
+
+static NORETURN void die_child(const char *err, va_list params)
+{
+       char msg[4096];
+       int len = vsnprintf(msg, sizeof(msg), err, params);
+       if (len > sizeof(msg))
+               len = sizeof(msg);
+
+       write(child_err, "fatal: ", 7);
+       write(child_err, msg, len);
+       write(child_err, "\n", 1);
+       exit(128);
+}
+
+static inline void set_cloexec(int fd)
+{
+       int flags = fcntl(fd, F_GETFD);
+       if (flags >= 0)
+               fcntl(fd, F_SETFD, flags | FD_CLOEXEC);
+}
+#endif
+
 int start_command(struct child_process *cmd)
 {
        int need_in, need_out, need_err;
@@ -79,6 +103,17 @@ int start_command(struct child_process *cmd)
        fflush(NULL);
        cmd->pid = fork();
        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) {
+                       child_err = dup(2);
+                       set_cloexec(child_err);
+               }
+               set_die_routine(die_child);
+
                if (cmd->no_stdin)
                        dup_devnull(0);
                else if (need_in) {
@@ -126,9 +161,14 @@ int start_command(struct child_process *cmd)
                } else {
                        execvp(cmd->argv[0], (char *const*) cmd->argv);
                }
-               trace_printf("trace: exec '%s' failed: %s\n", cmd->argv[0],
-                               strerror(errno));
-               exit(127);
+               /*
+                * Do not check for cmd->silent_exec_failure; the parent
+                * process will check it when it sees this exit code.
+                */
+               if (errno == 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],