Question

Looking for some help passing variables from one level to the next in a makefile. I have a source tree that needs to be built to run on various target architectures. To keep the higher level makefile clean I created separate makefiles that contain architecture specific information and include only the one that is required using the include directive 🙂

Later in the makefile I transfer to another directory to build the source files. The build fails and I see that the failure is caused by the architecture-specific variables not being passed.

ifeq ($(ARCH), my_arch)        |
include build/my_archdefs.mk   |  section 1 
endif                          |

<more commands>
debug:
      $(MAKE) -C src debug

The makefile to build the code tree is in the src directory. As a stop gap measure I included section 1 referenced above in the lower level makefile and in this case I noticed that the variable ARCH was not being passed down.

Here are a couple of links I found that seemed related but I’m not able to figure out what I need to do make this work.
http://www.gnu.org/software/make/manual/html_node/Options_002fRecursion.html#Options_002fRecursion
http://www.gnu.org/software/make/manual/html_node/Include.html

It seems to me that the info I need is lurking in the links I referenced above but I’m just not seeing it. Any pointers will be much appreciated.

Thanks.

Answer 1

This link should help: http://www.gnu.org/software/make/manual/html_node/Variables_002fRecursion.html#Variables_002fRecursion

In your top level Makefile just add the line export and all of your variables will be exported to your submakes.

Example:

File Makefile:

ID=asdf
export
all:
    @echo ${ID}
    @make -f Makefile2

File Makefile2:

all:
    @echo ${ID}

Output:

$ make
asdf
make[1]: Entering directory `/home/user/Desktop/a'
asdf
make[1]: Leaving directory `/home/user/Desktop/a'