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Too • today at 6:36 AM • 2 replies • view on HN

Can someone give a tldr of what makes fil-c different from just compiling with clang’s address sanitizer?

Calling it memory safe is a bit of a stretch when all it does is convert memory errors to runtime panics, or am I missing something? I mean, that’s still good, just less than I’d expect given the recent hype of fil-c being the savior for making C a competitive language again.

Replies

integralid • today at 7:57 AM

ASan does not make your code memory safe! It is quite good at catching unintentional bugs/oob memory writes in your code, and it is quite reliable (authors claim no false positives), but it has false negatives i.e. won't detect everything. Especially if you're against someone who tries to corrupt your memory intentionally.

ASan works by (simplifying a lot) padding allocations and surrounding them with untouchable "red zone". So with some luck even this can work:

  char *a = new char[100];
  char *b = new char[1000];
  a[500] = 0; // may end up in b
procaryote • today at 7:49 AM

If you can rely on memory errors panicing before the memory error can have an effect, you're memory safe. Memory safety doesn't require "can't crash".

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