On Sun, 2 Sep 2007, Mark Mitchell wrote: > Daniel Berlin wrote: > > > Again, I'd love to just ignore this and say "we don't care". > > Ugh. I think you're right that the standard says that we only get to > assume non-aliasing when the pointed-to memory is modified, so > all-parameters-restrict is actually weaker than -fargument-noalias. How > unfortunate. > > I've CC'd Joseph in the hopes that his C standards knowledge will > suggest a different answer.
The rules that unmodified memory may alias were a deliberate change in the FDIS relative to the previous public draft; see <http://www.open-std.org/jtc1/sc22/wg14/www/docs/n866.htm>: 24 1. The FCD specification of restrict forbids aliasing of 25 unmodified objects. Doing so does not promote optimization, 26 and has other disadvantages, which are discussed in examples 27 A-E below. It is also contrary to the prior art in Fortran. -- Joseph S. Myers [EMAIL PROTECTED]
