Suppress "make: Nothing to be done for 'target'"

Question

According to the GNUmake manual, 5.9 Using Empty Recipes, I can do the following to create an empty recipe:

target: ;

I have an empty recipe that prints system information to help in troubleshooting:

.PHONY: system
system: ;
    $(info CXX: $(CXX))
    $(info CXXFLAGS: $(CXXFLAGS))
    $(info GCC_COMPILER: $(GCC_COMPILER))
    $(info CLANG_COMPILER: $(CLANG_COMPILER))
    $(info INTEL_COMPILER: $(INTEL_COMPILER))
    $(info SUN_COMPILER: $(SUN_COMPILER))
    ...

However, it ends with:

...
IS_MINGW: 0
IS_CYGWIN: 1
IS_OPENBSD: 0
IS_SUN: 0
make: Nothing to be done for 'system'.

For some reason, I made the leap an empty rule would be silent (obviously wrong). Is there a way to suppress the message "Nothing to be done for 'target'"? If so, how?

Answer 1

You've given the system target a recipe by putting the $(info) lines under it. Make doesn't care that they are all make context and not shell context recipe lines though. That's why adding ; isn't doing anything. Your recipe is already not empty.

That all said you can either not use $(info) there and use @echo (or whatever) instead and you'll avoid that message.

Or you can go with just system: ; and then a make-level conditional on system being in MAKECMDGOALS to then use $(info) to display the information.

ifneq ($(filter system,$(MAKECMDGOALS)),)
    $(info CXX: $(CXX))
    $(info CXXFLAGS: $(CXXFLAGS))
    $(info GCC_COMPILER: $(GCC_COMPILER))
    $(info CLANG_COMPILER: $(CLANG_COMPILER))
    $(info INTEL_COMPILER: $(INTEL_COMPILER))
    $(info SUN_COMPILER: $(SUN_COMPILER))
endif

system: ;

Which would then let you use make target1 target2 system and get the system output printed before the targets are run.

The above does output

make: `system' is up to date.

at the end though. To avoid that you need to actually give the rule a recipe.

system: ;@:

but that will actually run a shell (the empty recipe does not). So you get to decide on the trade-offs there.