diff -urN sdlmame-0.146/src/emu/emu.mak sdlmame-0.146-patched/src/emu/emu.mak
--- sdlmame-0.146/src/emu/emu.mak	2012-05-27 11:21:30.449383001 +1100
+++ sdlmame-0.146-patched/src/emu/emu.mak	2012-05-27 11:24:40.060141002 +1100
@@ -125,6 +125,8 @@
 	$(EMUOBJ)/profiler.o \
 	$(OSDOBJ)/osdepend.o \
 	$(OSDOBJ)/osdnet.o
+
+$(EMUOBJ)/ioport.o : CCOMFLAGS += -O0
 
 EMUSOUNDOBJS = \
 	$(EMUOBJ)/sound/filter.o \