Re: [Opensync-devel] new printf format checks and compiler settings

[Daniel G. <go...@b1...>]

On Friday 13 November 2009 10:30:03 pm Chris Frey wrote:
> On Thu, Nov 12, 2009 at 04:36:40PM -0500, Chris Frey wrote:
> > I think the GCC_FORMAT_CHECK is worth it in the long run (there were lots
> > of printf style errors in the code), but the (void*) casts are
> > unfortunate. Anyone know of a cleaner workaround?
> 
> After a conversation on #gcc on irc.freenode.net (thanks to segher),
> I had the following enlightenment:
> 
>         - the C standard does not guarantee that all pointers are the same
>                 size on all platforms
> 
>         - for example, data pointers and function pointers can have
>  differing formats
> 
>         - the C standard guarantees that you can cast all pointers to void*
>                 and back
> 
>         - the %p format string identifier only takes a void*
> 
>         - vararg functions cannot provide implicit casts, since there is
>                 no prototype for the variable data
> 
>         - so in general, to be standard-C correct, you need to cast all
>                 %p pointers to vararg functions
> 
>         - the -pedantic option makes all this show up explicitly, but in
>                 most cases you don't need it, at least with gcc
> 
> Basically there's no way around it, except disabling -pedantic in your
> compiles, or adding (void*) casts to all %p pointers.
> 

Thank you very much for sharing this knowledge!

Best Regards,
Daniel

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