hush: stop generating extra empty pipes in parse stage.

diff --git a/shell/hush.c b/shell/hush.c
index eb6f37f15673128fa820b8960313ea24b9b6a933..a299b012393c600068fec2bc87be290a4a74192a 100644 (file)
--- a/shell/hush.c
+++ b/shell/hush.c
@@ -2685,8 +2685,8 @@ static int done_command(struct p_context *ctx)
                 && child->argv == NULL
                 && child->redirects == NULL
                ) {
-                       debug_printf_parse("done_command: skipping null command\n");
-                       return 0;
+                       debug_printf_parse("done_command: skipping null cmd, num_progs=%d\n", pi->num_progs);
+                       return pi->num_progs;
                }
                pi->num_progs++;
                debug_printf_parse("done_command: ++num_progs=%d\n", pi->num_progs);
@@ -2712,26 +2712,28 @@ static int done_command(struct p_context *ctx)
        ctx->child = child;
        /* but ctx->pipe and ctx->list_head remain unchanged */
 
-       return 0;
+       return pi->num_progs; /* used only for 0/nonzero check */
 }
 
 static int done_pipe(struct p_context *ctx, pipe_style type)
 {
        struct pipe *new_p;
+       int not_null;
 
        debug_printf_parse("done_pipe entered, followup %d\n", type);
-       done_command(ctx);  /* implicit closure of previous command */
+       not_null = done_command(ctx);  /* implicit closure of previous command */
        ctx->pipe->followup = type;
        ctx->pipe->r_mode = ctx->res_w;
-       new_p = new_pipe();
-       ctx->pipe->next = new_p;
-       ctx->pipe = new_p;
-       ctx->child = NULL;
-// TODO: even just <enter> on command line basically generates
-// tree of three NOPs (!).
-// Can we detect that previous done_command have seen "skipping null command"
-// condition and NOT create new pipe here?
-       done_command(ctx);  /* set up new pipe to accept commands */
+       /* Without this check, even just <enter> on command line generates
+        * tree of three NOPs (!). Which is harmless but annoying.
+        * IOW: it is safe to do it unconditionally. */
+       if (not_null) {
+               new_p = new_pipe();
+               ctx->pipe->next = new_p;
+               ctx->pipe = new_p;
+               ctx->child = NULL;
+               done_command(ctx);  /* set up new pipe to accept commands */
+       }
        debug_printf_parse("done_pipe return 0\n");
        return 0;
 }