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einpoklum
einpoklum

Reputation: 131525

target_compile_definitions for multiple CMake targets?

I've been told it's bad practice to do things like seting CFLAGS directly in CMake, and that, instead, I should use the target_compile_definitions() command.

Ok, but - what if I want to use similar/identical definitions for multiple (independent) targets? I don't want to repeat myself over and over again.

Upvotes: 4

Views: 9437

Answers (3)

einpoklum
einpoklum

Reputation: 131525

tl;dr: You can iterate the targets in a loop.

If you have a bunch of targets with some common/similar features, you may want to simply manipulate them all in a loop! Remember - CMake is not like GNU Make, it's a full-fledged scripting language (well, sort of). So you could write:

set(my_targets
    foo
    bar
    baz)

foreach(TARGET ${my_targets})
    add_executable(${TARGET} "${TARGET}.cu")
    target_compile_options(${TARGET} PRIVATE "--some_option=some_value")
    target_link_libraries(${TARGET} PRIVATE some_lib)
    # and so on
    set_target_properties(
        ${TARGET}
        PROPERTIES
        C_STANDARD 99
        C_STANDARD_REQUIRED YES
        C_EXTENSIONS NO )
endforeach(TARGET)

And you could also initialize an empty list of targets, then add to it here-and-there, and only finally apply your common options and settings to all of them, centrally.

Note: In this example I added PRIVATE compile options, but if you need some of them to propagate to targets using your targets, you can make them PUBLIC).

Upvotes: 3

demon36
demon36

Reputation: 425

another neat solution is to define an interface library target (a fake target that does not produce any binaries) with all required properties and compiler definitions, then link the other existing targets against it

example:

add_library(myfakelib INTERFACE)
target_compile_definitions(myfakelib INTERFACE MY_NEEDED_DEFINITION)

add_executable(actualtarget1 main1.cpp)
add_executable(actualtarget2 main2.cpp)

set_property(
    TARGET actualtarget1 actualtarget2
    APPEND PROPERTY LINK_LIBRARIES myfakelib
)

refs:

https://cmake.org/cmake/help/latest/command/add_library.html#interface-libraries

Upvotes: 1

Florian
Florian

Reputation: 42852

I see three possible ways:

  1. The preferred one using target_compile_definitions(... INTERFACE/PUBLIC ...) which would self-propagate the compiler definitions to targets depending on it via target_link_libraries() command.

  2. Using the set_property(TARGET target1 target2 ... APPEND PROPERTY COMPILE_DEFINITIONS ...) to set the same definitions to multiple targets.

  3. You may still use the "old commands" of add_definitions() and remove_definitions() to modify COMPILE_DEFINITIONS directory property (which would pre-set all COMPILE_DEFINITIONS target properties in this directories scope).

References

Upvotes: 8

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