GCC's include option with CMake

CMakeLists.txt

cmake_minimum_required(VERSION 3.10)

project(gcc-include-demo CXX)

if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
    # Make sure it's specified before add_executable.
    # Includes pre-main.inc.cpp in all translation units in all projects.
    # Use target_compile_options to include it in all translation units for a specific target only.
    add_compile_options(-include pre-main.inc.cpp)
else()
    error("Only GCC is supported")
endif()

add_executable(main main.cpp)

main.cpp

int main() {
    run();
}

pre-main.inc.cpp

#include <cstdio>

void run() {
    std::printf("run()\n");
}