cmake add_library 具有最低 cpp 标准

Question

library needs atleast cpp14 but if cpp17 is available, it unlocks more features. I tried the below.

cmake_minimum_required(VERSION 3.10)
project(dummy)

add_library(awesomelib STATIC awesomelib.cpp awesomelib.h)
target_compile_features(awesomelib INTERFACE cxx_std_14)

add_executable(dummy14 main.cpp)
target_link_libraries(dummy14 awesomelib)
target_compile_features(dummy14 PRIVATE cxx_std_14)

add_executable(dummy17 main.cpp)
target_link_libraries(dummy17 awesomelib)
target_compile_features(dummy17 PRIVATE cxx_std_17)

What I want is:

1. dummy14 to compile using the C++14 standard
2. dummy17 and awesomelib to compile using the C++17 standard

But what happens is that awesomelib is compiled (only once) according to the c++14 std.

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Update

I have shown the executables in the same file for simplicity. In real setup, the library would be in a separate project/repository and the users will be in a different project. I am looking for how the library can advertise its minimum requirements. ie it needs at least c++14 standard and depending on the user, it has to be compiled with whatever latest version the user has.

Answer 1

I added a few changes to your CMkaeLists.txt file and it seems to work now

cmake_minimum_required(VERSION 3.10)
project(dummy)
set (CMAKE_CXX_STANDARD 17)

add_library(awesomelib STATIC awesomelib.cpp awesomelib.h)
target_compile_features(awesomelib INTERFACE)

add_executable(dummy17 main.cpp)
target_link_libraries(dummy17 awesomelib)
target_compile_features(dummy17 PRIVATE cxx_std_17)

set (CMAKE_CXX_STANDARD 14)
add_executable(dummy14 main.cpp)
target_link_libraries(dummy14 awesomelib)
target_compile_features(dummy14 PRIVATE cxx_std_14)