On 13/12/2013, at 12:32 AM, srean wrote:
> A rough idea of the problem: in C you're not allowed to index
> past the end of an array. So strictly speaking this code is not
> conforming C:
>
> struct X { char a[1]; };
> struct X *p = malloc(100);
> char a = p->a[2]; // array is only 1 long!
>
> I have heard that this gets used in C a lot, what is the intended purpose of
> such code ?
Dynamic allocation of a structure containing a variable length array at the end.
Used in many thing, for example almost all serialisation formats, such as ACN
1.1 I guess.
A common representation of strings (length bytes followed by the string).
It is possible to do all this without such structures. It is possible to do all
of
C using pointers and casts. Its just harder to read.
C89 doesn't have any support for this. You can have variable length
arrays as function arguments, but not elsewhere (eg not in structures).
--
john skaller
[email protected]
http://felix-lang.org
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