Starting yesterday(ish), i've been getting this from OSX 10.6.6
make TARGET=mess PTR64=1

/snip
Compiling src/mess/drivers/smc777.c...
cc1plus: warnings being treated as errors
src/mess/drivers/smc777.c: In function �UINT32 video_update_smc777(screen_device*, bitmap_t*, const rectangle*)�:
src/mess/drivers/smc777.c:137: warning: �bk_pen� may be used uninitialized in this function
{standard input}:unknown:Undefined local symbol LC16
{standard input}:unknown:Undefined local symbol LC19
make: *** [obj/sdl/mess64/mess/drivers/smc777.o] Error 1
/snip