[Zlib-devel] zlib 1.2.3.5 available for testing

[Mark Adler]

On Jan 8, 2010, at 2:11 AM, Török Edwin wrote:
> 1. Portability
> gzread.c:425:13: warning: use of GNU void* extension [-Wpointer-arith]
>        buf += n;
>        ~~~ ^  ~
> 
> gzwrite.c:195:17: warning: use of GNU void* extension [-Wpointer-arith]
>            buf += n;
>            ~~~ ^  ~

What I had there before which worked fine a few years ago was:

    (char *)buf += n;

Makes sense, right?  Well now I get a nastygram from the compiler for that: "warning: target of assignment not really an lvalue; this will be a hard error in the future."  So I changed it to:

    buf += n;

but apparently some compilers hate that as well.  It used to be that any self-respecting compiler knew what you meant when you did arithmetic on a void * pointer, i.e. that you meant for the units to be bytes.  And I have no idea why (char *)buf, a cast of a pointer to another pointer type, is no longer a pointer.  Why there has been such a vicious attack on the expressiveness of C, I have no idea.  I blame it all on religious extremists.  Anyway, I digress.  Please try this in those two places:

    buf = (char *)buf + n;

and let me know what complaint you get then.  Thanks.

Mark