kc3-lang/SDL

2021-07-30T22:31:17

render: Fix -Wmaybe-uninitialized warning in RenderDrawLinesWithRects{,F} The RenderDrawLinesWithRects and RenderDrawLinesWithRectsF functions can sometimes call QueueCmdFillRects() with the data pointed to by frects uninitialised. This can occur if none of the lines can be replaced with rects, in which case the frects array is empty, and nrects is 0. gcc 10.3.0 will detect this possibility, and print a warning like: /home/david/Development/SDL/src/render/SDL_render.c: In function 'RenderDrawLinesWithRectsF': /home/david/Development/SDL/src/render/SDL_render.c:2725:15: warning: '<unknown>' may be used uninitialized [-Wmaybe-uninitialized] 2725 | retval += QueueCmdFillRects(renderer, frects, nrects); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ /home/david/Development/SDL/src/render/SDL_render.c:499:1: note: by argument 2 of type 'const SDL_FRect *' to 'QueueCmdFillRects' declared here 499 | QueueCmdFillRects(SDL_Renderer *renderer, const SDL_FRect * rects, const int count) | ^~~~~~~~~~~~~~~~~ This is harmless, because when this is uninitialised, nrects is always 0, so QueueCmdFillRects() does nothing anyway. We therefore can work around this by only calling QueueCmdFillRects() when nrects is nonzero. Somewhat impressively, gcc recognises that this is now safe.

diff --git a/src/render/SDL_render.c b/src/render/SDL_render.c
index 305267d..d111e77 100644
--- a/src/render/SDL_render.c
+++ b/src/render/SDL_render.c
@@ -2666,7 +2666,9 @@ RenderDrawLinesWithRects(SDL_Renderer * renderer,
         }
     }
 
-    retval += QueueCmdFillRects(renderer, frects, nrects);
+    if (nrects) {
+        retval += QueueCmdFillRects(renderer, frects, nrects);
+    }
 
     SDL_small_free(frects, isstack);
 
@@ -2721,7 +2723,9 @@ RenderDrawLinesWithRectsF(SDL_Renderer * renderer,
         }
     }
 
-    retval += QueueCmdFillRects(renderer, frects, nrects);
+    if (nrects) {
+        retval += QueueCmdFillRects(renderer, frects, nrects);
+    }
 
     SDL_small_free(frects, isstack);