build: Define cc-option-add to immediately add options to CFLAGS

without deferring the test execution of CC. This avoids extra
executions of CC every time CFLAGS is expanded.

Signed-off-by: Keir Fraser <keir.fraser@citrix.com>

Config.mk

@@ -38,6 +38,15 @@ endif
 cc-option = $(shell if test -z "`$(1) $(2) -S -o /dev/null -xc \
               /dev/null 2>&1`"; then echo "$(2)"; else echo "$(3)"; fi ;)
 
+# cc-option-add: Add an option to compilation flags, but only if supported.
+# Usage: $(call cc-option-add CFLAGS,CC,-march=winchip-c6)
+cc-option-add = $(eval $(call cc-option-add-closure,$(1),$(2),$(3)))
+define cc-option-add-closure
+    ifneq ($$(call cc-option,$$($(2)),$(3),n),n)
+        $(1) += $(3)
+    endif
+endef
+
 # cc-ver: Check compiler is at least specified version. Return boolean 'y'/'n'.
 # Usage: ifeq ($(call cc-ver,$(CC),0x030400),y)
 cc-ver = $(shell if [ $$((`$(1) -dumpversion | awk -F. \
@@ -84,8 +93,8 @@ CFLAGS += -Wall -Wstrict-prototypes
 # result of any casted expression causes a warning.
 CFLAGS += -Wno-unused-value
 
-HOSTCFLAGS += $(call cc-option,$(HOSTCC),-Wdeclaration-after-statement,)
-CFLAGS     += $(call cc-option,$(CC),-Wdeclaration-after-statement,)
+$(call cc-option-add,HOSTCFLAGS,HOSTCC,-Wdeclaration-after-statement)
+$(call cc-option-add,CFLAGS,CC,-Wdeclaration-after-statement)
 
 LDFLAGS += $(foreach i, $(EXTRA_LIB), -L$(i)) 
 CFLAGS += $(foreach i, $(EXTRA_INCLUDES), -I$(i))

tools/firmware/Rules.mk

@@ -13,9 +13,9 @@ endif
 CFLAGS += -Werror
 
 # Disable PIE/SSP if GCC supports them. They can break us.
-CFLAGS += $(call cc-option,$(CC),-nopie,)
-CFLAGS += $(call cc-option,$(CC),-fno-stack-protector,)
-CFLAGS += $(call cc-option,$(CC),-fno-stack-protector-all,)
+$(call cc-option-add,CFLAGS,CC,-nopie)
+$(call cc-option-add,CFLAGS,CC,-fno-stack-protector)
+$(call cc-option-add,CFLAGS,CC,-fno-stack-protector-all)
 
 # Extra CFLAGS suitable for an embedded type of environment.
 CFLAGS += -fno-builtin -msoft-float

tools/tests/blowfish.mk

@@ -5,9 +5,9 @@ CFLAGS =
 include $(XEN_ROOT)/tools/Rules.mk
 
 # Disable PIE/SSP if GCC supports them. They can break us.
-CFLAGS += $(call cc-option,$(CC),-nopie,)
-CFLAGS += $(call cc-option,$(CC),-fno-stack-protector,)
-CFLAGS += $(call cc-option,$(CC),-fno-stack-protector-all,)
+$(call cc-option-add,CFLAGS,CC,-nopie)
+$(call cc-option-add,CFLAGS,CC,-fno-stack-protector)
+$(call cc-option-add,CFLAGS,CC,-fno-stack-protector-all)
 
 CFLAGS += -fno-builtin -msoft-float
 

tools/vnet/libxutil/Makefile

@@ -24,7 +24,8 @@ LIB_SRCS += util.c
 LIB_OBJS := $(LIB_SRCS:.c=.o)
 PIC_OBJS := $(LIB_SRCS:.c=.opic)
 
-CFLAGS   += -Werror -fno-strict-aliasing $(call cc-option,$(CC),-fgnu89-inline,)
+$(call cc-option-add,CFLAGS,CC,-fgnu89-inline)
+CFLAGS   += -Werror -fno-strict-aliasing
 CFLAGS   += -O3
 #CFLAGS   += -g
 

xen/arch/x86/Rules.mk

@@ -26,9 +26,9 @@ CFLAGS += -I$(BASEDIR)/include/asm-x86/mach-default
 CFLAGS += -msoft-float
 
 # Disable PIE/SSP if GCC supports them. They can break us.
-CFLAGS += $(call cc-option,$(CC),-nopie,)
-CFLAGS += $(call cc-option,$(CC),-fno-stack-protector,)
-CFLAGS += $(call cc-option,$(CC),-fno-stack-protector-all,)
+$(call cc-option-add,CFLAGS,CC,-nopie)
+$(call cc-option-add,CFLAGS,CC,-fno-stack-protector)
+$(call cc-option-add,CFLAGS,CC,-fno-stack-protector-all)
 
 ifeq ($(supervisor_mode_kernel),y)
 CFLAGS += -DCONFIG_X86_SUPERVISOR_MODE_KERNEL=1