如果您使用的是CMake 3.1.0或更高版本,您可以检测您的C++编译器支持哪些C++特性。
cmake_minimum_required(VERSION 3.1.0 FATAL_ERROR)
project(foobar CXX)
message("Your C++ compiler supports these C++ features:")
foreach(i ${CMAKE_CXX_COMPILE_FEATURES})
message("${i}")
endforeach()
通常情况下,在CMake脚本中不需要使用CMake变量CMAKE_CXX_COMPILE_FEATURES。取而代之,有两种方法告诉CMake在哪个C++标准下编译您的C++文件:一种是明确指定C++标准,另一种是指定所需的C++功能,让CMake引导C++标准。CMake将确保使用正确的命令行标志(例如-std=c++11)调用C++编译器。
- 显式指定C++标准
您可以通过设置CMake目标的属性CXX_STANDARD和CXX_STANDARD_REQUIRED来明确指定C++标准。
$ cat /tmp/src/CMakeLists.txt
project(foobar CXX)
cmake_minimum_required(VERSION 3.1.0 FATAL_ERROR)
add_executable(prog main.cc)
set_property(TARGET prog PROPERTY CXX_STANDARD 11)
set_property(TARGET prog PROPERTY CXX_STANDARD_REQUIRED ON)
$ cat /tmp/src/main.cc
int main() {
return 0;
}
$ mkdir /tmp/build
$ cd /tmp/build
$ cmake /tmp/src
-- The CXX compiler identification is GNU 4.8.2
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Configuring done
-- Generating done
-- Build files have been written to: /tmp/build
$ make VERBOSE=1 | grep main.cc | grep -- "-c"
/usr/bin/c++ -std=gnu++11 -o CMakeFiles/prog.dir/main.cc.o -c /tmp/src/main.cc
$
- 使用CMake命令target_compile_features指定所需的C++功能。从列表中,CMake将推断要使用的C++标准。CMake全局属性CMAKE_CXX_KNOWN_FEATURES列出了可供选择的C++功能。
cmake_minimum_required(VERSION 3.1.0 FATAL_ERROR)
message("Your CMake version supports these C++ features:")
get_property(known_features GLOBAL PROPERTY CMAKE_CXX_KNOWN_FEATURES)
foreach(i ${known_features})
message("${i}")
endforeach()
例如,这个文件名为main.cc的C++程序使用了C++11的特性:
cxx_strong_enums,cxx_constexpr,cxx_auto_type
#include <cstdlib>
int main(int argc, char *argv[]) {
enum class Color { Red, Orange, Yellow, Green, Blue, Violet };
constexpr float a = 3.1415f;
auto b = a;
return EXIT_SUCCESS;
}
这个 CMakeLists.txt 文件将会构建它
cmake_minimum_required(VERSION 3.1.0 FATAL_ERROR)
project(foobar CXX)
add_executable(foobar main.cc)
set(needed_features
cxx_strong_enums
cxx_constexpr
cxx_auto_type)
target_compile_features(foobar PRIVATE ${needed_features})
add_definitions
命令而不是设置CMAKE_CXX_FLAGS
来设置编译器选项? - Li Dong