Re: make: variable assignment after target?

[Paul D. Smith]

%% michalk@awpi.com (Brian K. Michalk) writes:

  bkm> I want to do something like this:
  bkm> ----------------
  bkm> INCLUDEDIR = $(KERNELDIR)/include
  bkm> all: module
  bkm> module: dm5806_20040322.o dm5806_20040820.o
  bkm> dm5806_20040322.o: dm5806.c
  bkm> KERNELDIR := /usr/src/20040322
  bkm>      gcc $(CFLAGS) -o dm5806_20040322.o dm5806.c

  bkm> dm5806_20040820.o: dm5806.c
  bkm> KERNELDIR := /usr/src/20040820
  bkm>      gcc $(CFLAGS) -o dm5806_20040820.o dm5806.c
  bkm> ----------------

  bkm> I want to have several kernel source trees, and compile modules
  bkm> against the various trees, where INCLUDEDIR is deferred, and then
  bkm> KERNELDIR is set after the target is known, however this is not
  bkm> allowed.

If INCLUDEDIR is only used within command scripts and isn't used in
target or prerequisite lists, you can use target-specific variables.
See the GNU make manual for details.

 INCLUDEDIR = $(KERNELDIR)/include
 all: module
 module: dm5806_20040322.o dm5806_20040820.o

 dm5806_20040322.o: KERNELDIR := /usr/src/20040322
 dm5806_20040322.o: dm5806.c
      gcc $(CFLAGS) -o dm5806_20040322.o dm5806.c

 dm5806_20040820.o: KERNELDIR := /usr/src/20040820
 dm5806_20040820.o: dm5806.c
      gcc $(CFLAGS) -o dm5806_20040820.o dm5806.c


Note you need a recent version of GNU make for this to work.

-- 
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 Paul D. Smith <psmith@gnu.org>          Find some GNU make tips at:
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