Compile features and C/C++ standard selection

Syntax#

• target_compile_features(target PRIVATE|PUBLIC|INTERFACE feature1 [feature2 …])

Compile Feature Requirements

Required compiler features can be specified on a target using the command target_compile_features:

add_library(foo
    foo.cpp
)
target_compile_features(foo
    PRIVATE          # scope of the feature
    cxx_constexpr    # list of features
)

The features must be part of CMAKE_C_COMPILE_FEATURES or CMAKE_CXX_COMPILE_FEATURES; cmake reports an error otherwise. Cmake will add any necessary flags such as -std=gnu++11 to the compile options of the target.

In the example, the features are declared PRIVATE: the requirements will be added to the target, but not to its consumers. To automatically add the requirements to a target building against foo, PUBLIC or INTERFACE should be used instead of PRIVATE:

target_compile_features(foo
    PUBLIC    # this time, required as public
    cxx_constexpr
)

add_executable(bar
    main.cpp
)
target_link_libraries(bar
    foo       # foo's public requirements and compile flags are added to bar
)

C/C++ version selection

Wanted version for C and C++ can be specified globally using respectively variables CMAKE_C_STANDARD (accepted values are 98, 99 and 11) and CMAKE_CXX_STANDARD (accepted values are 98, 11 and 14):

set(CMAKE_C_STANDARD 99)
set(CMAKE_CXX_STANDARD 11)

These will add the needed compile options on targets (e.g. -std=c++11 for gcc).

The version can be made a requirement by setting to ON the variables CMAKE_C_STANDARD_REQUIRED and CMAKE_CXX_STANDARD_REQUIRED respectively.

The variables must be set before target creation. The version can also be specified per-target:

set_target_properties(foo PROPERTIES
    CXX_STANDARD 11
    CXX_STANDARD_REQUIRED ON
)