ubuntu gcc from apt issue

CMakeLists.txt

cmake_minimum_required(VERSION 3.0)
project(project)

set(CMAKE_VERBOSE_MAKEFILE ON)

# a shared library
add_library(lib SHARED lib.cpp)

add_executable(main main.cpp)

# link with lib
target_link_libraries(main PRIVATE lib)

lib.cpp

#include <iostream>

static void func() { std::cout << "\n\n\n\nfuncfucnfucn\n\n\n\n"; }

// run before main expectedly !
static int dummy = (func(), 0);

main.cpp

#include <iostream>

int main(int argc, char *argv[]) {
  std::cout << "main" << std::endl;
  return 0;
}

if you compile this project using gcc/g++ from apt install gcc g++, the func() in lib.cpp will not run expectedly

> ./build/main 
main

but with manually compiled gcc or gcc from conda, yoiu will get evertything work

> ./build/main 




funcfucnfucn



main

without cmake

/usr/bin/g++ lib.cpp --shared -fPIC -o liblib.so
/usr/bin/g++ main.cpp -l lib -o main