Comment by amiga386

A simple example would be that the function glGetString(GL_EXTENSIONS) crashes the original Quake engine and many licensees, because it's expecting no more than a 256 character string.

The driver looks to see if a known old game is calling it, and if it's one known to crash, it returns no more than 256 characters, and likely also puts all the _old_ extensions that the game is likely to know and react to in the string.

There are also all sorts of games that called APIs in a particular order or set particular options, because they represented a "fast path" at the time, and now they don't, but if you're that program, then yes they do.

Ultimately, this clutter is what let do the development of the Vulcan API, to stop games second-guessing graphics APIs which themselves second-guess the games.