Clean up the usage of z_const and respect const usage within zlib.

This patch allows zlib to compile cleanly with the -Wcast-qual gcc
warning enabled, but only if ZLIB_CONST is defined, which adds
const to next_in and msg in z_stream and in the in_func prototype.
A --const option is added to ./configure which adds -DZLIB_CONST
to the compile flags, and adds -Wcast-qual to the compile flags
when ZLIBGCCWARN is set in the environment.

1 files changed, 2 insertions, 1 deletions

diff --git a/zlib.h b/zlib.h
index cd47df5..55e3c2c 100644
--- a/zlib.h
+++ b/zlib.h
@@ -1022,7 +1022,8 @@ ZEXTERN int ZEXPORT inflateBackInit OF((z_streamp strm, int windowBits,
    the version of the header file.
 */
 
-typedef unsigned (*in_func) OF((void FAR *, unsigned char FAR * FAR *));
+typedef unsigned (*in_func) OF((void FAR *,
+                                z_const unsigned char FAR * FAR *));
 typedef int (*out_func) OF((void FAR *, unsigned char FAR *, unsigned));
 
 ZEXTERN int ZEXPORT inflateBack OF((z_streamp strm,