From: Eli Zaretskii <eliz@gnu.org>
Date: Tue, 8 Sep 2020 16:17:23 +0000 (+0300)
Subject: Avoid crashes when trying to load bad GIF files
X-Git-Tag: emacs-27.1.90~156
X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=366a97c980f068a3ed665d337d644ee58cd25ca0;p=emacs.git

Avoid crashes when trying to load bad GIF files

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

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. */