Brian Dessent wrote:
Thank you Brian. But sigh, it is just a workaround but not a perfect
solution. In your method, you refrain from using cflags until
the final stage(executing a rule), and in middle stages you stick to default_cflags
, but what if in some middle stage I want to to filter-out something
else? Then I have to introduce yet another variable. Don't you think
Just introduce another variable.
default_cflags = -c -DNDEBUG -O2
cflags = $(default_cflags)
my.obj: cflags = $(LateDef) $(filter-out -DNDEBUG,$(default_cflags))
Compile my.obj: -D LATEDEF1 -D LATEDEF2 -c -O2
Compile his.obj: -c -DNDEBUG -O2
linking my.obj his.obj
For example, a modification:
### special >>>
LateDef += -D LATEDEF1
my.obj: cflags := $(LateDef) $(filter-out -DNDEBUG,$(cflags))
default_cflags := $(filter-out -O2,$(default_cflags)) # Oops.
LateDef += -D LATEDEF2
### special <<<
So, it's best to add a new operator to makefile syntax , e.g.
myvar @= $(call someprocessing,$(myvar),...)
myvar @= $(myvar) abc # the same effect as ``+='' operator
Explain: address@hidden'' is like ``='', a delayed expansion, but when a
recursive situation is encountered on expansion, the recursed variable
reports its current value; and, after the expansion the recursed
variable is updated according to the @= _expression_. This way we can
eliminate many cases drawing intermediate variables to our makefiles.
I hope make's current developers can consider this.