Richard Guenther wrote: >> What is an example program in that meets the requirements I gave above >> -- i.e., allows the compiler to prove that two same-typed pointers do >> not alias (whether by the compiler's cleverness, use of "restrict", or >> whatever), but where the compiler must still assume that the values of >> the pointers might be the same? > > I see I misinterpreted your sentence. I don't think a testcase that > holds all your requirements can be constructed as they > contradict each other. Can you give one?
No -- I don't think any such test case should exist. But, IIUC, one of your proposals could lead to the existence of such a test case. In particular, I understood you to be suggesting that we might be able to make the "malloc" attribute work for any implementation of "operator new" by saying that while the compiler could assume that "*p" and "*q" did not alias, the compiler was none-the-less not allowed to assume that "p != q". My point was that this seems like a very strange requirement to impose on the compiler, and that the compiler -- now, or in future -- is very likely to make exactly that deduction, since it is logically true. More broadly, my point was that a universe in which "*p does not alias *q" fails to imply "p != q", for "p" and "q" pointers of the same type, is a weird place to be. -- Mark Mitchell CodeSourcery [EMAIL PROTECTED] (650) 331-3385 x713
