On 04/23/2010 11:27 AM, Simon Josefsson wrote: > Not gnulib specific, but related to our coding style: > > Does POSIX somewhere guarantee that the in-memory representation of NULL > pointers is 0? I know that C89 doesn't make that guarantee, and that > some historic systems used non-0 memory values to represent NULL, but > I'm hoping that this is not permitted today by some standard.
I think POSIX currently sticks by the same weasel-wording as C99, and allows a weirdnix system where the in-memory representation of NULL is not all 0 bits. > > I believe there is a bunch of places in gnulib which uses memset(P, 0, > sizeof(P)) to initialize structures containing pointers, which wouldn't > be OK if this is not the case. However, GNU Coding Standards states that we can assume that all platforms worth porting to obey the industry convention that NULL maps to all 0 bits, so even if POSIX doesn't guarantee it, gnulib is safe using the idiom. -- Eric Blake ebl...@redhat.com +1-801-349-2682 Libvirt virtualization library http://libvirt.org
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