[ufo]

It helps optimization. One example is if you have code like this:

    if(condition) {
       error_stuff()
       abort();
    }
    normal_stuff();

If the compiler doesn't know that abort exits the program, they have to compile the normal_stuff path under the assumption that the error path might have run before it. This might result in suboptimal code.

Currently, many compilers support annotations such as __attribute__(noreturn) and __builtin_unreachable() to manually indicate that a code path is unreachable. C23 is now standardizing these features (with a slight tweak to the syntax).