ANSI C, hardware protection, out-of-bounds pointers

[Doug Gwyn]

In article <9520 at chinet.chi.il.us> kdb at chinet.chi.il.us (Karl Botts) writes:
>Any standard implementation of malloc() et al. puts either the size
>of the block or a pointer to the next block in the machine word just
>before the start of the block ...

Not true.  A "buddy system" allocator is MOST unlikely to do so.

>Thus you can be sure that mentioning this word (or even dereferencing it)
>will not cause an exception.

Even in such cases, it still wouldn't help with arrays of large objects,
because first-1 would point many bytes below the start of the allocated
data block.

Just don't use first-1.  It's not that hard to avoid.