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

diff --git a/run-command.c b/run-command.c
index f3e7abb7de799a14a8f792195992c4d9d1495c6f..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;
@@ -75,10 +99,21 @@ int start_command(struct child_process *cmd)
 
        trace_argv_printf(cmd->argv, "trace: run_command:");
 
-#ifndef __MINGW32__
+#ifndef WIN32
        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) {
@@ -126,14 +161,20 @@ 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],
                        strerror(failed_errno = errno));
 #else
+{
        int s0 = -1, s1 = -1, s2 = -1;  /* backups of stdin, stdout, stderr */
        const char **sargv = cmd->argv;
        char **env = environ;
@@ -173,11 +214,8 @@ int start_command(struct child_process *cmd)
 
        if (cmd->dir)
                die("chdir in start_command() not implemented");
-       if (cmd->env) {
-               env = copy_environ();
-               for (; *cmd->env; cmd->env++)
-                       env = env_setenv(env, *cmd->env);
-       }
+       if (cmd->env)
+               env = make_augmented_environ(cmd->env);
 
        if (cmd->git_cmd) {
                cmd->argv = prepare_git_cmd(cmd->argv);
@@ -200,6 +238,7 @@ int start_command(struct child_process *cmd)
                dup2(s1, 1), close(s1);
        if (s2 >= 0)
                dup2(s2, 2), close(s2);
+}
 #endif
 
        if (cmd->pid < 0) {
@@ -316,8 +355,8 @@ int run_command_v_opt_cd_env(const char **argv, int opt, const char *dir, const
        return run_command(&cmd);
 }
 
-#ifdef __MINGW32__
-static __stdcall unsigned run_thread(void *data)
+#ifdef WIN32
+static unsigned __stdcall run_thread(void *data)
 {
        struct async *async = data;
        return async->proc(async->fd_for_proc, async->data);
@@ -332,7 +371,7 @@ int start_async(struct async *async)
                return error("cannot create pipe: %s", strerror(errno));
        async->out = pipe_out[0];
 
-#ifndef __MINGW32__
+#ifndef WIN32
        /* Flush stdio before fork() to avoid cloning buffers */
        fflush(NULL);
 
@@ -361,7 +400,7 @@ int start_async(struct async *async)
 
 int finish_async(struct async *async)
 {
-#ifndef __MINGW32__
+#ifndef WIN32
        int ret = wait_or_whine(async->pid, "child process", 0);
 #else
        DWORD ret = 0;