Eric Blake <ebl...@redhat.com> writes: > 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.
Darn. >> 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. Right. The portability assumptions for a project becomes a bit more complicated to explain though. Thanks, /Simon
