Makefile ifeq logical or

by

As found on the mailing list archive,

one can use the filter function.

For example

ifeq ($(GCC_MINOR),$(filter $(GCC_MINOR),4 5))

filter X, A B will return those of A,B that are equal to X.
Note, while this is not relevant in the above example, this is a XOR operation. I.e. if you instead have something like:

ifeq (4, $(filter 4, $(VAR1) $(VAR2)))

And then do e.g. make VAR1=4 VAR2=4, the filter will return 4 4, which is not equal to 4.

A variation that performs an OR operation instead is:

ifneq (,$(filter $(GCC_MINOR),4 5))

where a negative comparison against an empty string is used instead (filter will return en empty string if GCC_MINOR doesn’t match the arguments). Using the VAR1/VAR2 example it would look like this:

ifneq (, $(filter 4, $(VAR1) $(VAR2)))

The downside to those methods is that you have to be sure that these arguments will always be single words. For example, if VAR1 is 4 foo, the filter result is still 4, and the ifneq expression is still true. If VAR1 is 4 5, the filter result is 4 5 and the ifneq expression is true.

One easy alternative is to just put the same operation in both the ifeq and else ifeq branch, e.g. like this:

ifeq ($(GCC_MINOR),4)
    @echo Supported version
else ifeq ($(GCC_MINOR),5)
    @echo Supported version
else
    @echo Unsupported version
endif

More Related Contents:

  1. What is the purpose of .PHONY in a Makefile?
  2. Make error: missing separator
  3. Passing additional variables from command line to make
  4. OS detecting makefile
  5. What is the difference between the GNU Makefile variable assignments =, ?=, := and +=?
  6. Define make variable at rule execution time
  7. What do @, – and + do as prefixes to recipe lines in Make?
  8. How to generate a Makefile with source in sub-directories using just one makefile
  9. What do the makefile symbols $@ and $< mean?
  10. GNU Makefile rule generating a few targets from a single source file
  11. What’s the opposite of ‘make install’, i.e. how do you uninstall a library in Linux?
  12. Make: how to continue after a command fails?
  13. Difference between CPPFLAGS and CXXFLAGS in GNU Make
  14. Create directories using make file
  15. Passing the argument to CMAKE via command prompt
  16. How to get current relative directory of your Makefile?
  17. Best practice for building a make file
  18. Why .SECONDARY does not work with patterns (%) while .PRECIOUS does?
  19. Difference in details between “make install” and “make altinstall”
  20. Building C-program “out of source tree” with GNU make
  21. make *** no targets specified and no makefile found. stop
  22. CFLAGS vs CPPFLAGS
  23. CMAKE_MAKE_PROGRAM not found
  24. Makefile header dependencies
  25. How to print out a variable in makefile
  26. Why are .PHONY implicit pattern rules not triggered?
  27. Force gnu make to rebuild objects affected by compiler definition
  28. Make error of mixed implicit and normal rules
  29. Generic rule from makefile to CMake
  30. tar: file changed as we read it

Leave a Comment