mutt: Fix the hcache type punning warning.

[Brendan Cully]

changeset: 6397:cc7903944687
user:      Kevin McCarthy <ke...@8t8.us>
date:      Sat Jan 17 14:42:28 2015 -0800
link:      http://dev.mutt.org/hg/mutt/rev/cc7903944687

Fix the hcache type punning warning.

This patch fixes the type punning warning by switching from (safe but
perhaps not elegant) casting to using a union.

Thanks to Vincent Lefevre for his input and suggestion to use the union
as a better solution to the problem!

diffs (26 lines):

diff -r d732298789f2 -r cc7903944687 hcache.c
--- a/hcache.c  Thu Jan 15 13:19:14 2015 +0100
+++ b/hcache.c  Sat Jan 17 14:42:28 2015 -0800
@@ -1135,7 +1135,10 @@
 
   /* Calculate the current hcache version from dynamic configuration */
   if (hcachever == 0x0) {
-    unsigned char digest[16];
+    union {
+      unsigned char charval[16];
+      unsigned int intval;
+    } digest;
     struct md5_ctx ctx;
     SPAM_LIST *spam;
     RX_LIST *nospam;
@@ -1161,8 +1164,8 @@
     }
 
     /* Get a hash and take its bytes as an (unsigned int) hash version */
-    md5_finish_ctx(&ctx, digest);
-    hcachever = *((unsigned int *)digest);
+    md5_finish_ctx(&ctx, digest.charval);
+    hcachever = digest.intval;
   }
 
   h->db = NULL;