cmake generator expression for target architecture? - c++

Question

Is there a modern approach to use target architecture within a condition for a generator expression in CMake? There are some answers that are somewhat outdated. I am looking for a modern or at least very robust and reliable custom script for using target architecture within a generator expression.
The docs do not seem to contain that kind of info.
One of the ideas for a workaround I see is to use $<<STRING:MY_DETECTED_ARCH:ARCH_ARM>:src_for_arm.cpp>

Answer 1

I checked a solution from this answer and it worked.
cmake_minimum_required(VERSION 3.14.2 FATAL_ERROR)
project(cmake_target_arch)
set(CMAKE_CXX_STANDARD 17)
include(TargetArch.cmake)
target_architecture(TARGET_ARCH)
message(STATUS "target_architecture: ${TARGET_ARCH}")
add_executable(cmake_target_arch
main.cpp
$<$<STREQUAL:"${TARGET_ARCH}","x86_64">:x86_64.cpp>
$<$<STREQUAL:"${TARGET_ARCH}","i386">:i386.cpp>
$<$<STREQUAL:"${TARGET_ARCH}","armv7">:armv7.cpp>
)
main.cpp
#include <iostream>
#include <string>
extern std::string hello_message();
int main()
{
std::cout << hello_message() << std::endl;
return 0;
}
i386.cpp
#include <string>
std::string hello_message()
{
return "Hello i386!";
}
Example output for i386 binary:
C:\Users\serge\dev\repos\cmake_target_arch\cmake-build-release-visual-studio-win32\cmake_target_arch.exe
Hello i386!
I guess one can come up with a CMake Macro to wrap strings comparison