Exit status by convention has integer zero to represent “OK” no error status. Non-zero status is generally considered a failure. Coding languages such as Fortran also have built-in syntax to manage program exit code returned to the operating system.

C++ defines EXIT_SUCCESS and EXIT_FAILURE macros in header cstdlib. C defines EXIT_SUCCESS and EXIT_FAILURE macros in header stdlib.h.

Because typical headers already included often #include <cstdlib> or #include <stdlib.h>, developers may not realize these exit status macros need to be included somewhere. As compilers transition to providing stdlib via C++20 modules and generally cleanup excessive includes from built-in headers, code may suddenly complain about missing exit status macros at build time.

We feel it’s a good practice to use exit status macros as a findable and readable indication that program flow is ending and returning to system. A best practice is to include the appropriate header in any code file where the exit status macros are used.

#include <stdlib.h>

int main(void){
  return EXIT_SUCCESS;
}

#include <cstdlib>

int main(){
  return EXIT_SUCCESS;
}