#include <cstdlib>
#include <iostream>
#include <string>
std::string say_hello() {
#ifdef IS_INTEL_CXX_COMPILER
// only compiled when Intel compiler is selected
// such compiler will not compile the other branches
return std::string("Hello Intel compiler!");
#elif IS_GNU_CXX_COMPILER
// only compiled when GNU compiler is selected
// such compiler will not compile the other branches
return std::string("Hello GNU compiler!");
#elif IS_PGI_CXX_COMPILER
// etc.
return std::string("Hello PGI compiler!");
#elif IS_XL_CXX_COMPILER
return std::string("Hello XL compiler!");
#else
return std::string("Hello unknown compiler - have we met before?");
#endif
}
int main() {
std::cout << say_hello() << std::endl;
std::cout << "compiler name is " COMPILER_NAME << std::endl;
return EXIT_SUCCESS;
}
Fortran示例(hello-world.F90):
program hello
implicit none
#ifdef IS_Intel_FORTRAN_COMPILER
print *, 'Hello Intel compiler!'
#elif IS_GNU_FORTRAN_COMPILER
print *, 'Hello GNU compiler!'
#elif IS_PGI_FORTRAN_COMPILER
print *, 'Hello PGI compiler!'
#elif IS_XL_FORTRAN_COMPILER
print *, 'Hello XL compiler!'
#else
print *, 'Hello unknown compiler - have we met before?'
#endif
end program
具体实施
我们将从C++的例子开始，然后再看Fortran的例子:
CMakeLists.txt文件中，定义了CMake最低版本、项目名称和支持的语言:
cmake_minimum_required(VERSION 3.5 FATAL_ERROR)
project(recipe-03 LANGUAGES CXX)
然后，定义可执行目标及其对应的源文件:
add_executable(hello-world hello-world.cpp)
通过定义以下目标编译定义，让预处理器了解编译器的名称和供应商:
target_compile_definitions(hello-world PUBLIC "COMPILER_NAME=\"${CMAKE_CXX_COMPILER_ID}\"")
if(CMAKE_CXX_COMPILER_ID MATCHES Intel)
target_compile_definitions(hello-world PUBLIC "IS_INTEL_CXX_COMPILER")
endif()
if(CMAKE_CXX_COMPILER_ID MATCHES GNU)
target_compile_definitions(hello-world PUBLIC "IS_GNU_CXX_COMPILER")
endif()
if(CMAKE_CXX_COMPILER_ID MATCHES PGI)
target_compile_definitions(hello-world PUBLIC "IS_PGI_CXX_COMPILER")
endif()
if(CMAKE_CXX_COMPILER_ID MATCHES XL)
target_compile_definitions(hello-world PUBLIC "IS_XL_CXX_COMPILER")
endif()
现在我们已经可以预测结果了:
$ mkdir -p build
$ cd build
$ cmake ..
$ cmake --build .
$ ./hello-world
Hello GNU compiler!