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Comment by dependenttypes | Hacker News Reader

> since C doesn't ... check for overflows

Because it's a language, not an implementation. An implementation is free to do so (and there are such implementations after all).

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That's correct! C doesn't require checking for overflows, but it also doesn't forbid implementations from doing so. both are features.

I don’t think it is possible, not without changing some parts of the C’s specification. At the very least you’d need to be able to somehow encode the length of the buffer in the pointer to it. (There is no semantic difference between a pointer to a simple, fixed-length variable and a pointer to an array.)

Which is what the article proposed.

You can keep a list of every allocation and every time the code does a memory read/write the implementation can look up to see if the pointer is within a valid allocation space. I have implemented some things like this: https://www.youtube.com/watch?v=pvkn9Xz-xks

Which is what hardware implementations like Solaris SPARC do.

void f(size_t n, int v[n]) is valid C.

Semantically though, the second argument is still just a naked pointer.

That’s why you use the proper declaration of

  void f(size_t n, int (*v)[n])

instead.

Is it? I am pretty sure that v[x] where x >= n is UB.

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