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Comment by hoppelhase | Hacker News Reader

Well, both implementations do have a strict which has the length as last member. Is there any special reason for it? Something like struct-layout optimization?

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You can re-interpret the struct to a pointer (length would simply be truncated). Apart from that there wouldn't be any benefit: the pointer and length would be aligned no matter which position they take (on x86 and amd64 at the very least).

"re-interpret the struct to a pointer (length would simply be truncated)."

Wrong. It will be pointer-to-pointer.

Reinterpretation (to treat struct as a pointer to C string) is only possible if you have something like this:

    struct BSTR {
      size_t length;
      WCHAR  chars[N]; // N is length + 1     
    };

and you return pointer to chars[0]. This is so called Basic string - BSTR is a WCHAR* pointer to memory location prepended by string length field.

That's not what I was going after. You can treat the memory location (where the structure resides) as a pointer, plan and simple, nothing more fancy than what I said.

I don't think so. My guess would be that it is because a pointer to the struct can be cast to a pointer to T. I /think/ that is defined behaviour.

It is: https://port70.net/~nsz/c/c99/n1256.html#6.7.2.1p13

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