Question

I saw previous SO posts 1, 2 etc. I want to pass a preprocessor directive at compile time. With scons, I could do:

num_times = ARGUMENTS.get('c', 1)
env.Append(CCFLAGS = '-DNUM_TIMES=%d' % int(num_times))

I hope, it should also be possible using make. I want to issue

make c=4

or something like that. Can someone suggest a method. I am compiling a folder, which has subfolders with their own makefiles. Thanks in advance.

Answer 1

One simple approach is to do:

CFLAGS += -DNUM_TIMES=$(c)
export CFLAGS

all:
    $(MAKE) -C your_subfolder

call with make c=2, and not to touch CFLAGS in the sub-folder makefiles.

Another is to have a Makefile part in your root folder with all the common settings that you include in your subdirectory makefiles (with include). ($(MAKE) ensures that the command line arguments you gave to make will also be passed to sub-makes.)