Avoid crashes when trying to load bad GIF files

* src/image.c (gif_load): Handle the case when GifErrorString
returns NULL.  (Bug#43281)

1 files changed, 14 insertions, 10 deletions

diff --git a/src/image.c b/src/image.c
index 56878bcb8cb..956fb1325ed 100644
--- a/src/image.c
+++ b/src/image.c
@@ -8160,11 +8160,13 @@ gif_load (struct frame *f, struct image *img)
       if (gif == NULL)
         {
 #if HAVE_GIFERRORSTRING
-          image_error ("Cannot open `%s': %s",
-                       file, build_string (GifErrorString (gif_err)));
-#else
-          image_error ("Cannot open `%s'", file);
+          const char *errstr = GifErrorString (gif_err);
+          if (errstr)
+            image_error ("Cannot open `%s': %s", file, build_string (errstr));
+          else
 #endif
+          image_error ("Cannot open `%s'", file);
+
           return 0;
         }
     }
@@ -8190,11 +8192,13 @@ gif_load (struct frame *f, struct image *img)
       if (!gif)
         {
 #if HAVE_GIFERRORSTRING
-          image_error ("Cannot open memory source `%s': %s",
-                       img->spec, build_string (GifErrorString (gif_err)));
-#else
-          image_error ("Cannot open memory source `%s'", img->spec);
+          const char *errstr = GifErrorString (gif_err);
+          if (errstr)
+            image_error ("Cannot open memory source `%s': %s",
+                         img->spec, build_string (errstr));
+          else
 #endif
+          image_error ("Cannot open memory source `%s'", img->spec);
           return 0;
         }
     }
@@ -8474,9 +8478,9 @@ gif_load (struct frame *f, struct image *img)
       if (error_text)
         image_error ("Error closing `%s': %s",
                      img->spec, build_string (error_text));
-#else
-      image_error ("Error closing `%s'", img->spec);
+      else
 #endif
+      image_error ("Error closing `%s'", img->spec);
     }
 
   /* Maybe fill in the background field while we have ximg handy. */