diff -r b5bd25d55994 -r cb75b67f04fb make/bsd/makefiles/gcc.make
--- a/make/bsd/makefiles/gcc.make	Thu Mar 07 18:03:26 2013 -0800
+++ b/make/bsd/makefiles/gcc.make	Fri Mar 08 12:35:18 2013 -0500
@@ -168,12 +168,12 @@
 # conversions which might affect the values. To avoid that, we need to turn
 # it off explicitly. 
 ifneq "$(shell expr \( $(CC_VER_MAJOR) \> 4 \) \| \( \( $(CC_VER_MAJOR) = 4 \) \& \( $(CC_VER_MINOR) \>= 3 \) \))" "0"
-ACCEPTABLE_WARNINGS = -Wpointer-arith -Wsign-compare
+WARNING_FLAGS = -Wpointer-arith -Wsign-compare -Wundef
 else
-ACCEPTABLE_WARNINGS = -Wpointer-arith -Wconversion -Wsign-compare
+WARNING_FLAGS = -Wpointer-arith -Wconversion -Wsign-compare -Wundef
 endif
 
-CFLAGS_WARN/DEFAULT = $(WARNINGS_ARE_ERRORS) $(ACCEPTABLE_WARNINGS)
+CFLAGS_WARN/DEFAULT = $(WARNINGS_ARE_ERRORS) $(WARNING_FLAGS)
 # Special cases
 CFLAGS_WARN/BYFILE = $(CFLAGS_WARN/$@)$(CFLAGS_WARN/DEFAULT$(CFLAGS_WARN/$@)) 
 # XXXDARWIN: for _dyld_bind_fully_image_containing_address