-WARNING_OPTS += -optc-Wall
-WARNING_OPTS += -optc-W
-WARNING_OPTS += -optc-Wstrict-prototypes
-WARNING_OPTS += -optc-Wmissing-prototypes
-WARNING_OPTS += -optc-Wmissing-declarations
-WARNING_OPTS += -optc-Winline
-WARNING_OPTS += -optc-Waggregate-return
-#WARNING_OPTS += -optc-Wpointer-arith
-WARNING_OPTS += -optc-Wbad-function-cast
-#WARNING_OPTS += -optc-Wcast-align
-#WARNING_OPTS += -optc-Wnested-externs
-#WARNING_OPTS += -optc-Wshadow
-#WARNING_OPTS += -optc-Wcast-qual
-#WARNING_OPTS += -optc-Wno-unused
-#WARNING_OPTS += -optc-Wredundant-decls
-#WARNING_OPTS += -optc-Wconversion
-
-SRC_HC_OPTS += -I../includes -I. -Iparallel $(WARNING_OPTS) $(GhcRtsHcOpts) -optc-DCOMPILING_RTS
-SRC_CC_OPTS = $(GhcRtsCcOpts)
+WARNING_OPTS += -Wall
+WARNING_OPTS += -W
+WARNING_OPTS += -Wstrict-prototypes
+WARNING_OPTS += -Wmissing-prototypes
+WARNING_OPTS += -Wmissing-declarations
+WARNING_OPTS += -Winline
+WARNING_OPTS += -Waggregate-return
+#WARNING_OPTS += -Wpointer-arith
+WARNING_OPTS += -Wbad-function-cast
+#WARNING_OPTS += -Wcast-align
+#WARNING_OPTS += -Wnested-externs
+#WARNING_OPTS += -Wshadow
+#WARNING_OPTS += -Wcast-qual
+#WARNING_OPTS += -Wno-unused
+#WARNING_OPTS += -Wredundant-decls
+#WARNING_OPTS += -Wconversion
+
+STANDARD_OPTS += -I../includes -I. -Iparallel
+# COMPILING_RTS is only used when building Win32 DLL support.
+STANDARD_OPTS += -DCOMPILING_RTS
+
+ifeq "$(HOSTPLATFORM)" "i386-unknown-mingw32"
+STANDARD_OPTS += -Iwin32
+endif
+
+# HC_OPTS is included in both .c and .cmm compilations, whereas CC_OPTS is
+# only included in .c compilations. HC_OPTS included the WAY_* opts, which
+# must be included in both types of compilations.
+
+SRC_CC_OPTS += $(WARNING_OPTS)
+SRC_CC_OPTS += $(STANDARD_OPTS)
+
+SRC_CC_OPTS += $(GhcRtsCcOpts)
+SRC_HC_OPTS += $(GhcRtsHcOpts)