Added some commentary about new libpng warnings.

diff --git a/coders/png.c b/coders/png.c
index 4b6d7da82c3376464127b42869ac048bbb455e54..8ba13704ff5fb77757f7fa77a74b8bce18df1d62 100644 (file)
--- a/coders/png.c
+++ b/coders/png.c
@@ -80,12 +80,16 @@
 #include "magick/utility.h"
 #if defined(MAGICKCORE_PNG_DELEGATE)
 
-/* Suppress libpng pedantic warnings */
-#define PNG_DEPRECATED  /* use of this function is deprecated */
-#define PNG_USE_RESULT  /* the result of this function must be checked */
-#define PNG_NORETURN    /* this function does not return */
-#define PNG_ALLOCATED   /* the result of the function is new memory */
-#define PNG_DEPSTRUCT   /* access to this struct member is deprecated */
+/* Suppress libpng pedantic warnings that were added in
+ * libpng-1.2.41 and libpng-1.4.0.  If you are working on
+ * migration to libpng-2.0, remove these defines and then
+ * fix any code that generates warnings.
+ */
+#define PNG_DEPRECATED  /* Use of this function is deprecated */
+#define PNG_USE_RESULT  /* The result of this function must be checked */
+#define PNG_NORETURN    /* This function does not return */
+#define PNG_ALLOCATED   /* The result of the function is new memory */
+#define PNG_DEPSTRUCT   /* Access to this struct member is deprecated */
 
 #include "png.h"
 #include "zlib.h"