On: ELF hash function may overflow

[kevin_thibedeau]

The base integer types have always been open ended since C89. It has always been wrong to assume an exact size when writing code that depends on modular wraparound. The code is wrong.

Prior to stdint.h there was no portable way to address this but new code should be written using the type system as intended. Open ended when the minimum is sufficient and larger storage is inconsequential. Exact size when the algorithm requires it.

[marginalia_nu → kevin_thibedeau]

The code isn't wrong, it's platform dependent. It's the assumption that it that is wrong. The code itself if is fine.

[layer8 → marginalia_nu]

If the assumptions made by the code are wrong, the code is wrong.

I would agree with you if the code would preprocessor-check ULONG_MAX and #error out if it isn’t the expected value.

[marginalia_nu → layer8]

The code isn't making assumptions, the programmer is.

[layer8 → marginalia_nu]

That’s all the same. Then the code the programmer is writing is wrong because the programmer’s assumptions are wrong. Potato, potahto.

[marginalia_nu → layer8]

There's actually a fairly big difference with the context of the language preventing the error.

If the code is wrong as in undefined behavior, then the compiler can and maybe should try to prevent it. If the programmer is wrong about the code, then the compiler can't and definitely shouldn't try to prevent it.

In short, the compiler can't prevent this

  int is_empty(char* s) {
    return strlen(s) > 10;
  }

The compiler maybe could prevent this:

  is_empty(NULL);

[dahfizz → layer8]

Its not the same. The compiler can protect against code which is incorrect. The compiler cannot do anything to help with code that is correct but does the wrong thing.

[Joker_vD → marginalia_nu]

But if the code was written with intention to be platform-independent, and turned out to be platform-dependent... it's the programmer who wrote it is wrong, not the code itself? Or do I misunderstand you completely?

[marginalia_nu → Joker_vD]

Right.

Let's say I know the Swedish language, in which "öl" means "beer", and I travel to Germany to partake in the Oktoberfest celebrations. I arrive and in Germany and immediately try to order a beer and try to say "One Beer Please", but not mastering the language I say "Ein Öl Bitte" (meaning "one oil please"). I don't think the that's a bug in the German language, and the sentence itself is perfectly good German. It just doesn't say what I think it does.