[Zlib-devel] zlib 1.2.3.5 available for testing

[Vincent Torri]

On Fri, 8 Jan 2010, Mark Adler wrote:

> 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;
>>            ~~~ ^  ~

pointer arithmetic on void * is a gcc extension. It may give wrong results 
on other platforms (for exemple opensolaris using suncc, Enlightenment 
was not working because of that). Add -pedantic tovCFLAGS (when compiling 
with gcc). It removes the use of gcc extension andvyou'll see the warnings

just change the declaration of buf to be a char * instead of a void *

Vincent Torri

>
> 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
>
>
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