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>

1 files changed, 11 insertions, 2 deletions

diff --git a/Config.mk b/Config.mk
index 8768da26e1..2144513410 100644
--- a/Config.mk
+++ b/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))