From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Sat, 15 Aug 2009 00:19:32 GMT
Subject: Re: [PATCH] block-sha1/sha1.c: silence compiler complaints by casting void* to uintptr_t
Message-ID: <alpine.LFD.2.01.0908141714040.3162@localhost.localdomain>
In-Reply-To: <alpine.DEB.1.00.0908150207270.8306@pacific.mpi-cbg.de>



On Sat, 15 Aug 2009, Johannes Schindelin wrote:
> 
> I am confused.  Is sizeof(*(uintptr_t)NULL) not larger than 1

You can't do that. "uintptr_t" isn't actually a pointer. It's just a 
unsigned integer value large enough to contain a pointer.

So it's _not_ a "pointer to uint". It's "uint that can contain all the 
bits of a poitner".

> and as a consequence ((uintptr_t)p)+1 not different from ((void *)p)+1?

No, they're the same.

That said, I suspect it might as well be cast to "const char *", and then 
hopefully you only need one cast.

So maybe it could be written as

	data = (const char *) data + len;

instead, and avoid the second cast (because the assignment should be ok, 
since it's assigning back to a "const void *").

		Linus