zsnes: fix buffer size marking to avoid crash on _FORTIFY_SOURCE=3

Without the change `zsnesn` startup crashes with:

    $ gdb zsnes
    *** buffer overflow detected ***: terminated
    ...
    NixOS#7  0x08057c14 in memset (__len=2, __ch=255, __dest=<optimized out>) at
      ...-glibc-2.38-23-dev/include/bits/string_fortified.h:59

pkgs/applications/emulators/zsnes/default.nix

@@ -23,7 +23,10 @@ in stdenv.mkDerivation {
     sha256 = "1gy79d5wdaacph0cc1amw7mqm7i0716n6mvav16p1svi26iz193v";
   };
 
-  patches = [ ./zlib-1.3.patch ];
+  patches = [
+    ./zlib-1.3.patch
+    ./fortify3.patch
+  ];
 
   buildInputs = [ nasm SDL zlib libpng ncurses libGLU libGL ];
 

pkgs/applications/emulators/zsnes/fortify3.patch

@@ -0,0 +1,29 @@
+pal16bxcl is an array of 256 dwords, not bytes:
+    src/endmem.asm:NEWSYM pal16bxcl, resd 256
+
+While at it fixes off-by-4 out of bounds exit.
+
+Detected by _FORTIFY_SOURCE=3:
+    *** buffer overflow detected ***: terminated
+    #7  0x08057c14 in memset (__len=2, __ch=255, __dest=<optimized out>) at ...-glibc-2.38-23-dev/include/bits/string_fortified.h:59
+#8  clearmem () at initc.c:1461
+--- a/src/initc.c
++++ b/src/initc.c
+@@ -1389,7 +1389,7 @@ extern unsigned char vidmemch8[4096];
+ extern unsigned char pal16b[1024];
+ extern unsigned char pal16bcl[1024];
+ extern unsigned char pal16bclha[1024];
+-extern unsigned char pal16bxcl[256];
++extern unsigned char pal16bxcl[1024];
+ extern unsigned char SPCRAM[65472];
+ unsigned char *SPCState = SPCRAM;
+
+@@ -1456,7 +1456,7 @@ void clearmem()
+   memset(pal16b, 0, 1024);
+   memset(pal16bcl, 0, 1024);
+   memset(pal16bclha, 0, 1024);
+-  for (i=0 ; i<1024 ; i+=4)
++  for (i=0 ; i<1024-4 ; i+=4)
+   {
+     memset(pal16bxcl+i, 255, 2);
+     memset(pal16bxcl+i+2, 0, 2);