VVVVVV/desktop_version/src/Unreachable.h

#ifndef UNREACHABLE_H
#define UNREACHABLE_H

#include <SDL_stdinc.h>

SDL_NORETURN SDL_INLINE void VVV_unreachable(void)
{
    /* __builtin_unreachable() and __assume(0) execute undefined behavior.
     * Otherwise, a noreturn function returning is also undefined behavior. */
#if _SDL_HAS_BUILTIN(__builtin_unreachable)
    __builtin_unreachable();
#elif defined(_MSC_VER)
    __assume(0);
#endif
}

#endif /* UNREACHABLE_H */
Add Unreachable.h This is to indicate when a code path is absolutely, for certain, 100% unreachable. Useful as the default case inside a case-switch that is for sure 100% exhaustive because it's inside the case of another case-switch (and the default case is there to suppress compiler warnings about the case-switch not being exhaustive), which is a situation coming up in my scriptclass::startgamemode refactor. It does this by deliberately invoking undefined behavior, either using a compiler builtin that does the same thing or being a noreturn function that returns. (And undefined behavior is not undefined behavior if it is not executed in a code path, otherwise all NULL checks would be useless because it'd dereference something that could be NULL in another code path.) 2022-12-29 12:10:25 -08:00			`#ifndef UNREACHABLE_H`
			`#define UNREACHABLE_H`

			`#include <SDL_stdinc.h>`

			`SDL_NORETURN SDL_INLINE void VVV_unreachable(void)`
			`{`
			`/* __builtin_unreachable() and __assume(0) execute undefined behavior.`
			`* Otherwise, a noreturn function returning is also undefined behavior. */`
Use _SDL_HAS_BUILTIN I think this is because if you both check that __has_builtin is defined and use it in the same 'if' preprocessor statement, it can error because there's no equivalent to short-circuiting in preprocessor statements. _SDL_HAS_BUILTIN should be safer. 2022-12-29 16:13:54 -08:00			`#if _SDL_HAS_BUILTIN(__builtin_unreachable)`
Add Unreachable.h This is to indicate when a code path is absolutely, for certain, 100% unreachable. Useful as the default case inside a case-switch that is for sure 100% exhaustive because it's inside the case of another case-switch (and the default case is there to suppress compiler warnings about the case-switch not being exhaustive), which is a situation coming up in my scriptclass::startgamemode refactor. It does this by deliberately invoking undefined behavior, either using a compiler builtin that does the same thing or being a noreturn function that returns. (And undefined behavior is not undefined behavior if it is not executed in a code path, otherwise all NULL checks would be useless because it'd dereference something that could be NULL in another code path.) 2022-12-29 12:10:25 -08:00			`__builtin_unreachable();`
			`#elif defined(_MSC_VER)`
			`__assume(0);`
			`#endif`
			`}`

			`#endif /* UNREACHABLE_H */`