How do I include all extensions my system supports using GLAD? When using the GLAD web service, I am allowed to pick any version of OpenGL and any extensions I want.

If I pick the latest version of OpenGL and "all extensions", will the header file returned by the Web Service #define extensions on my machine that I do not actually have or does it just define those that exist?

In other words, if I include the GL_ARB_SHADER_CLOCK extension, on GLAD, does it get defined even if not available on the machine I use?

I don't see how it could be selectively defining extensions because the script is generated on a server ahead of time but I want to make sure that I am not trying to use unsupported extensions.
In this github issue the GLAD author offers the following way to correctly check if there is an extension is available at runtime:


  The defines just allow you to check at compile time which extensions
  (and opengl versions) are potentially available. After
  loading/initilaizing glad you can check with GLAD_
  if the extension is available at runtime (= supported by the driver
  and loaded).

// [initialize glad] // ...
if (!GLAD_GL_EXT_memory_object) {
    die("GL_EXT_memory_object not supported!"); 
}