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, 3 insertions, 3 deletions

diff --git a/deflate.c b/deflate.c
index 4792345..4aa5afb 100644
--- a/deflate.c
+++ b/deflate.c
@@ -305,7 +305,7 @@ int ZEXPORT deflateInit2_(strm, level, method, windowBits, memLevel, strategy,
     if (s->window == Z_NULL || s->prev == Z_NULL || s->head == Z_NULL ||
         s->pending_buf == Z_NULL) {
         s->status = FINISH_STATE;
-        strm->msg = (char*)ERR_MSG(Z_MEM_ERROR);
+        strm->msg = ERR_MSG(Z_MEM_ERROR);
         deflateEnd (strm);
         return Z_MEM_ERROR;
     }
@@ -329,7 +329,7 @@ int ZEXPORT deflateSetDictionary (strm, dictionary, dictLength)
     uInt str, n;
     int wrap;
     unsigned avail;
-    unsigned char *next;
+    z_const unsigned char *next;
 
     if (strm == Z_NULL || strm->state == Z_NULL || dictionary == Z_NULL)
         return Z_STREAM_ERROR;
@@ -359,7 +359,7 @@ int ZEXPORT deflateSetDictionary (strm, dictionary, dictLength)
     avail = strm->avail_in;
     next = strm->next_in;
     strm->avail_in = dictLength;
-    strm->next_in = (Bytef *)dictionary;
+    strm->next_in = (z_const Bytef *)dictionary;
     fill_window(s);
     while (s->lookahead >= MIN_MATCH) {
         str = s->strstart;