From c727965c62ca86924a4bdbf5f32fe47182aa2666 Mon Sep 17 00:00:00 2001
From: Dirk Lemstra <dirk@git.imagemagick.org>
Date: Sat, 31 Mar 2018 15:24:38 +0200
Subject: [PATCH] Return null in GetImageDecoder when magick_info is null.

---
 MagickCore/constitute.c | 19 +++++++++++--------
 MagickCore/magick.c     |  3 ++-
 2 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/MagickCore/constitute.c b/MagickCore/constitute.c
index bf38b18df..3477daa74 100644
--- a/MagickCore/constitute.c
+++ b/MagickCore/constitute.c
@@ -372,6 +372,9 @@ MagickExport Image *ReadImage(const ImageInfo *image_info,
   const MagickInfo
     *magick_info;
 
+  DecodeImageHandler
+    *decoder;
+
   ExceptionInfo
     *sans_exception;
 
@@ -477,8 +480,8 @@ MagickExport Image *ReadImage(const ImageInfo *image_info,
       image=DestroyImage(image);
     }
   image=NewImageList();
-  if ((magick_info == (const MagickInfo *) NULL) ||
-      (GetImageDecoder(magick_info) == (DecodeImageHandler *) NULL))
+  decoder=GetImageDecoder(magick_info);
+  if (decoder == (DecodeImageHandler *) NULL)
     {
       delegate_info=GetDelegateInfo(read_info->magick,(char *) NULL,exception);
       if (delegate_info == (const DelegateInfo *) NULL)
@@ -487,14 +490,14 @@ MagickExport Image *ReadImage(const ImageInfo *image_info,
           (void) CopyMagickString(read_info->filename,filename,
             MagickPathExtent);
           magick_info=GetMagickInfo(read_info->magick,exception);
+          decoder=GetImageDecoder(magick_info);
         }
     }
-  if ((magick_info != (const MagickInfo *) NULL) &&
-      (GetImageDecoder(magick_info) != (DecodeImageHandler *) NULL))
+  if (decoder != (DecodeImageHandler *) NULL)
     {
       if (GetMagickDecoderThreadSupport(magick_info) == MagickFalse)
         LockSemaphoreInfo(magick_info->semaphore);
-      image=GetImageDecoder(magick_info)(read_info,exception);
+      image=decoder(read_info,exception);
       if (GetMagickDecoderThreadSupport(magick_info) == MagickFalse)
         UnlockSemaphoreInfo(magick_info->semaphore);
     }
@@ -537,8 +540,8 @@ MagickExport Image *ReadImage(const ImageInfo *image_info,
       if (status != MagickFalse)
         (void) SetImageInfo(read_info,0,exception);
       magick_info=GetMagickInfo(read_info->magick,exception);
-      if ((magick_info == (const MagickInfo *) NULL) ||
-          (GetImageDecoder(magick_info) == (DecodeImageHandler *) NULL))
+      decoder=GetImageDecoder(magick_info);
+      if (decoder == (DecodeImageHandler *) NULL)
         {
           if (IsPathAccessible(read_info->filename) != MagickFalse)
             (void) ThrowMagickException(exception,GetMagickModule(),
@@ -552,7 +555,7 @@ MagickExport Image *ReadImage(const ImageInfo *image_info,
         }
       if (GetMagickDecoderThreadSupport(magick_info) == MagickFalse)
         LockSemaphoreInfo(magick_info->semaphore);
-      image=(Image *) (GetImageDecoder(magick_info))(read_info,exception);
+      image=(Image *) (decoder)(read_info,exception);
       if (GetMagickDecoderThreadSupport(magick_info) == MagickFalse)
         UnlockSemaphoreInfo(magick_info->semaphore);
     }
diff --git a/MagickCore/magick.c b/MagickCore/magick.c
index bd33ce389..a3eea1ea6 100644
--- a/MagickCore/magick.c
+++ b/MagickCore/magick.c
@@ -215,7 +215,8 @@ MagickExport MagickInfo *AcquireMagickInfo(const char *module,const char *name,
 */
 MagickExport DecodeImageHandler *GetImageDecoder(const MagickInfo *magick_info)
 {
-  assert(magick_info != (MagickInfo *) NULL);
+  if (magick_info == (MagickInfo *) NULL)
+    return((DecodeImageHandler *) NULL);
   assert(magick_info->signature == MagickCoreSignature);
   return(magick_info->decoder);
 }
-- 
2.40.0