[Xen-devel] [PATCH] xen/Rules.mk: Do not dance about pointlessly with CFLAGS_tmp

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

It is usually better to use `=' in Makefiles than `:='.  The expansion
rules for `:=' are simpler - so simple in fact that they don't work if
any part of the expansion depends on the source or target filenames.

In this patch we remove the shuffling of the value of CFLAGS between
:= and = flavour variables.  This was previously `necessary' because
otherwise it would run the seddery for removing -fomit-frame-pointer
once for each rule.

However this seddery is not actually necessary because there is plenty
of other machinery for (a) only setting -fomit-frame-frame-pointer
when applicable AND (b) passing -fno-omit-frame-pointer later on the
command line if it's not applicable.  So we already have belt and
braces and can remove the safety pins.

Signed-off-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>

diff -r 95d8788bf4be xen/Rules.mk
--- a/xen/Rules.mk      Mon Jan 12 10:23:55 2009 +0000
+++ b/xen/Rules.mk      Mon Jan 12 16:58:48 2009 +0000
@@ -22,9 +22,6 @@ endif
 endif
 ifeq ($(perfc_arrays),y)
 perfc := y
-endif
-ifeq ($(frame_pointer),y)
-CFLAGS := $(shell echo $(CFLAGS) | sed -e 's/-f[^ ]*omit-frame-pointer//g')
 endif
 
 # Set ARCH/SUBARCH appropriately.
@@ -64,14 +61,11 @@ AFLAGS-y                += -D__ASSEMBLY_
 
 ALL_OBJS := $(ALL_OBJS-y)
 
-CFLAGS_tmp := $(strip $(CFLAGS) $(CFLAGS-y))
-CFLAGS = $(CFLAGS_tmp) -MMD -MF .$(@F).d
+CFLAGS += $(CFLAGS-y) -MMD -MF .$(@F).d
 
 # Most CFLAGS are safe for assembly files:
 #  -std=gnu{89,99} gets confused by #-prefixed end-of-line comments
-AFLAGS_tmp := $(strip $(AFLAGS) $(AFLAGS-y))
-AFLAGS_tmp += $(patsubst -std=gnu%,,$(CFLAGS_tmp))
-AFLAGS = $(AFLAGS_tmp) -MMD -MF .$(@F).d
+AFLAGS += $(AFLAGS-y) $(filter-out -std=gnu%,$(CFLAGS))
 
 # LDFLAGS are only passed directly to $(LD)
 LDFLAGS  := $(strip $(LDFLAGS) $(LDFLAGS_DIRECT))

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