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

[Chris F. <cd...@fo...>]

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.

- Chris