hush: fix exit code propagation from `cmd`. +45 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 13 insertions, 2 deletions

diff --git a/shell/hush.c b/shell/hush.c
index ede8d680e..6dd6a0d03 100644
--- a/shell/hush.c
+++ b/shell/hush.c
@@ -3904,7 +3904,7 @@ static NOINLINE int run_pipe(struct pipe *pi)
                 /* if someone gives us an empty string: `cmd with empty output` */
                 if (!argv_expanded[0]) {
                         debug_leave();
-                        return 0; // or G.last_exitcode? see emptytick.tests
+                        return G.last_exitcode;
                 }
 
                 x = find_builtin(argv_expanded[0]);
@@ -6380,15 +6380,26 @@ static struct pipe *parse_stream(char **pstring,
  */
 static void parse_and_run_stream(struct in_str *inp, int end_trigger)
 {
+        /* Why we need empty flag?
+         * An obscure corner case "false; ``; echo $?":
+         * empty command in `` should still set $? to 0.
+         * But we can't just set $? to 0 at the start,
+         * this breaks "false; echo `echo $?`" case.
+         */
+        bool empty = 1;
         while (1) {
                 struct pipe *pipe_list;
 
                 pipe_list = parse_stream(NULL, inp, end_trigger);
-                if (!pipe_list) /* EOF */
+                if (!pipe_list) { /* EOF */
+                        if (empty)
+                                G.last_exitcode = 0;
                         break;
+                }
                 debug_print_tree(pipe_list, 0);
                 debug_printf_exec("parse_and_run_stream: run_and_free_list\n");
                 run_and_free_list(pipe_list);
+                empty = 0;
         }
 }