From: Simon Tatham <anakin@pobox.com>
Date: Sat, 22 Oct 2005 16:38:15 +0000 (+0000)
Subject: Noticed recently that bitcount16() isn't 16-bit clean due to signed
X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ian/git?a=commitdiff_plain;h=b44d75aa4e97e9264e585712a8ec5fa757b645ec;p=sgt-puzzles.git

Noticed recently that bitcount16() isn't 16-bit clean due to signed
shift right. It doesn't actually matter in the current code since
the input word only ever uses the bottom 9 bits, but if I ever
extended Mines to work in a triangular grid then all 16 bits might
be required. Fix this now, while I'm cleaning things up, so that it
won't bite me unexpectedly in future.

[originally from svn r6415]
---

diff --git a/mines.c b/mines.c
index 4210b56..b9bb7c9 100644
--- a/mines.c
+++ b/mines.c
@@ -275,14 +275,16 @@ static char *validate_params(game_params *params, int full)
 /*
  * Count the bits in a word. Only needs to cope with 16 bits.
  */
-static int bitcount16(int word)
+static int bitcount16(int inword)
 {
+    unsigned int word = inword;
+
     word = ((word & 0xAAAA) >> 1) + (word & 0x5555);
     word = ((word & 0xCCCC) >> 2) + (word & 0x3333);
     word = ((word & 0xF0F0) >> 4) + (word & 0x0F0F);
     word = ((word & 0xFF00) >> 8) + (word & 0x00FF);
 
-    return word;
+    return (int)word;
 }
 
 /*