winhelp: bug fix in LZ77 decompressor

[Kuba Ober]

> > >  Fix rather unusual bug in LZ77 decompressor. We cannot use
> > >  memcpy
> > > with overlapped areas because of unpredictable result. We must
> > > copy byte-by-byte.

> > Why don't you use memmove instead? The man page for memcpy says:
> > Use memmove(3) if the memory areas do overlap.

> We cannot use memmove. It provides different functionality. It moves
> blocks, but LZ77 decompress algorithm copies bytes.
>
> Let's suppose:
> 012
> XYZ
>
> When we say 'memmove(1, 0, 2)' we will get:
> 012
> XXY
>
> But we (LZ77 algorithm) expect:
> 012
> XXX (three 'X').
>
> memcpy is rather clever (it optmizes process by coping INT instead of
> BYTES). This optimization is fatal for LZ77.

Why?

Er, if the memcpy worked (or almost worked) and failed due to overlap 
problems, then memmove will do the trick. Did it ever work at all before? 
Either this code never worked, or you're either seeing a problem that doesn't 
exist/misunderstanding things.

Cheers, Kuba