[Mono-bugs] [Bug 48679][Maj] Changed - Unboxed bool is neither true nor false

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Changed by mass@akuma.org.

http://bugzilla.ximian.com/show_bug.cgi?id=48679

--- shadow/48679	2003-09-22 21:19:42.000000000 -0400
+++ shadow/48679.tmp.6778	2003-09-22 22:46:16.000000000 -0400
@@ -89,6 +89,39 @@
         static object compare(int a, int b)
         {
             return a >= b;
         }
 }
 
+
+------- Additional Comments From mass@akuma.org  2003-09-22 22:46 -------
+assembly generated for T::compare:
+
+   0:   55                      push   %ebp
+   1:   8b ec                   mov    %esp,%ebp
+   3:   83 ec 04                sub    $0x4,%esp
+   6:   68 1c 8e 12 08          push   $0x8128e1c
+   b:   e8 57 9e f9 37          call   37f99e67 
+<_T_compare+0x37f99e67>
+  10:   83 c4 04                add    $0x4,%esp
+  13:   89 45 fc                mov    %eax,0xfffffffc(%ebp)
+  16:   8b 4d 0c                mov    0xc(%ebp),%ecx
+  19:   39 4d 08                cmp    %ecx,0x8(%ebp)
+  1c:   0f 9c c1                setl   %cl
+  1f:   0f b6 c9                movzbl %cl,%ecx
+  22:   83 e9 01                sub    $0x1,%ecx
+  25:   88 48 08                mov    %cl,0x8(%eax)
+  28:   8b 45 fc                mov    0xfffffffc(%ebp),%eax
+  2b:   c9                      leave
+  2c:   c3                      ret
+
+two problems:
+22:   83 e9 01                sub    $0x1,%ecx
+
+this does %ecx = %ecx - 1, not %ecx = 1 - %ecx . This is why the 
+number returned with my unsafe cast above ends with 0xff
+
+25:   88 48 08                mov    %cl,0x8(%eax)
+
+this is the byte copy, not word copy. making the unsafe assumption 
+that the value that eax + 0x8 points to is not preset to zero, this 
+leaves garbage in the high bytes.