run-command: handle dup2 and close errors in child

Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: bmwill

run-command.c

@@ -213,6 +213,8 @@ static int child_notifier = -1;
 
 enum child_errcode {
 	CHILD_ERR_CHDIR,
+	CHILD_ERR_DUP2,
+	CHILD_ERR_CLOSE,
 	CHILD_ERR_ENOENT,
 	CHILD_ERR_SILENT,
 	CHILD_ERR_ERRNO
@@ -235,6 +237,24 @@ static void child_die(enum child_errcode err)
 	_exit(1);
 }
 
+static void child_dup2(int fd, int to)
+{
+	if (dup2(fd, to) < 0)
+		child_die(CHILD_ERR_DUP2);
+}
+
+static void child_close(int fd)
+{
+	if (close(fd))
+		child_die(CHILD_ERR_CLOSE);
+}
+
+static void child_close_pair(int fd[2])
+{
+	child_close(fd[0]);
+	child_close(fd[1]);
+}
+
 /*
  * parent will make it look like the child spewed a fatal error and died
  * this is needed to prevent changes to t0061.
@@ -277,6 +297,12 @@ static void child_err_spew(struct child_process *cmd, struct child_err *cerr)
 		error_errno("exec '%s': cd to '%s' failed",
 			    cmd->argv[0], cmd->dir);
 		break;
+	case CHILD_ERR_DUP2:
+		error_errno("dup2() in child failed");
+		break;
+	case CHILD_ERR_CLOSE:
+		error_errno("close() in child failed");
+		break;
 	case CHILD_ERR_ENOENT:
 		error_errno("cannot run %s", cmd->argv[0]);
 		break;
@@ -527,35 +553,35 @@ int start_command(struct child_process *cmd)
 		child_notifier = notify_pipe[1];
 
 		if (cmd->no_stdin)
-			dup2(null_fd, 0);
+			child_dup2(null_fd, 0);
 		else if (need_in) {
-			dup2(fdin[0], 0);
-			close_pair(fdin);
+			child_dup2(fdin[0], 0);
+			child_close_pair(fdin);
 		} else if (cmd->in) {
-			dup2(cmd->in, 0);
-			close(cmd->in);
+			child_dup2(cmd->in, 0);
+			child_close(cmd->in);
 		}
 
 		if (cmd->no_stderr)
-			dup2(null_fd, 2);
+			child_dup2(null_fd, 2);
 		else if (need_err) {
-			dup2(fderr[1], 2);
-			close_pair(fderr);
+			child_dup2(fderr[1], 2);
+			child_close_pair(fderr);
 		} else if (cmd->err > 1) {
-			dup2(cmd->err, 2);
-			close(cmd->err);
+			child_dup2(cmd->err, 2);
+			child_close(cmd->err);
 		}
 
 		if (cmd->no_stdout)
-			dup2(null_fd, 1);
+			child_dup2(null_fd, 1);
 		else if (cmd->stdout_to_stderr)
-			dup2(2, 1);
+			child_dup2(2, 1);
 		else if (need_out) {
-			dup2(fdout[1], 1);
-			close_pair(fdout);
+			child_dup2(fdout[1], 1);
+			child_close_pair(fdout);
 		} else if (cmd->out > 1) {
-			dup2(cmd->out, 1);
-			close(cmd->out);
+			child_dup2(cmd->out, 1);
+			child_close(cmd->out);
 		}
 
 		if (cmd->dir && chdir(cmd->dir))