New name UI_UPDATE for interpret_move's return "".

Now midend.c directly tests the returned pointer for equality to this
value, instead of checking whether it's the empty string.

A minor effect of this is that games may now return a dynamically
allocated empty string from interpret_move() and treat it as just
another legal move description. But I don't expect anyone to be
perverse enough to actually do that! The main purpose is that it
avoids returning a string literal from a function whose return type is
a pointer to _non-const_ char, i.e. we are now one step closer to
being able to make this code base clean under -Wwrite-strings.

1 files changed, 2 insertions, 2 deletions

diff --git a/unfinished/slide.c b/unfinished/slide.c
index 9d4fce1..51ac7cb 100644
--- a/unfinished/slide.c
+++ b/unfinished/slide.c
@@ -1349,7 +1349,7 @@ static char *interpret_move(const game_state *state, game_ui *ui,
 	 * And that's it. Update the display to reflect the start
 	 * of a drag.
 	 */
-	return "";
+	return UI_UPDATE;
     } else if (button == LEFT_DRAG && ui->dragging) {
 	int dist, distlimit, dx, dy, s, px, py;
 
@@ -1376,7 +1376,7 @@ static char *interpret_move(const game_state *state, game_ui *ui,
 		    if (px >= 0 && px < w && py >= 0 && py < h &&
 			ui->reachable[py*w+px]) {
 			ui->drag_currpos = py*w+px;
-			return "";
+			return UI_UPDATE;
 		    }
 		}
 	}