Build fails on OpenBSD

[bentley]

c++ -fvisibility-inlines-hidden -std=gnu++0x -O2 -pipe -g  -Wall -Wno-unused-function -ffast-math -fno-strict-aliasing -fvisibility=hidden -I../../src -I../../src/Glitch64/inc -DGCC -mmmx -msse -fPIC -I/usr/include -I/usr/local/include/libpng16 -I/usr/X11R6/include -I/usr/X11R6/include/libdrm -I/usr/local/include -I/usr/local/include/SDL2 -I/usr/X11R6/include -D_REENTRANT -I/usr/X11R6/include "-I/usr/local/include/mupen64plus" -g -DNO_ASM -MD -MP -D__unix__ -DTEXTURE_FILTER -DDUMP_CACHE  -c -o _obj/Glide64/Main.o ../../src/Glide64/Main.cpp
../../src/Glide64/Main.cpp:1187:38: error: cast from pointer to smaller type 'FxU32' (aka 'unsigned int') loses information
      gfx_context = grSstWinOpenExt ((FxU32)NULL,
                                     ^~~~~~~~~~~
../../src/Glide64/Main.cpp:1197:33: error: cast from pointer to smaller type 'FxU32' (aka 'unsigned int') loses information
    gfx_context = grSstWinOpen ((FxU32)NULL,
                                ^~~~~~~~~~~
2 errors generated.
gmake: *** [Makefile:488: _obj/Glide64/Main.o] Error 1

This is OpenBSD amd64, clang 4.0.0.