We will use the following C file (example.c) to print the version information:

#include "version.h"

#include <stdio.h>

int main() {
  printf("This is output from code %s\n", PROJECT_VERSION);
  printf("Major version number: %i\n", PROJECT_VERSION_MAJOR);
  printf("Minor version number: %i\n", PROJECT_VERSION_MINOR);

  printf("Hello CMake world!\n");
}

Here, we assume that PROJECT_VERSION_MAJOR, PROJECT_VERSION_MINOR, and PROJECT_VERSION are defined in version.h. Our goal is to generate version.h from the following scaffold, version.h.in:

#pragma once

#define PROJECT_VERSION_MAJOR @PROJECT_VERSION_MAJOR@
#define PROJECT_VERSION_MINOR @PROJECT_VERSION_MINOR@
#define PROJECT_VERSION_PATCH @PROJECT_VERSION_PATCH@

#define PROJECT_VERSION "v@PROJECT_VERSION@"

We will use preprocessor definitions, but we could also employ string or integer constants for more type safety (and we will demonstrate that later). From the CMake perspective, the approach is the same.