On Sat, Jan 29, 2011 at 2:24 AM, Robert Bradshaw <rober...@math.washington.edu> wrote: > On Fri, Jan 28, 2011 at 9:14 PM, Stefan Behnel <stefan...@behnel.de> wrote: >> Robert Bradshaw, 28.01.2011 22:49: >>> On Fri, Jan 28, 2011 at 1:01 PM, Stefan Behnel wrote: >>>> And given that Cython cannot know that the pointer is actually not a >>>> pointer, it generates the expected code here which only the C compiler can >>>> detect as invalid. >>>> This needs fixing in Sage in one way or another. >>> >>> Cython didn't used to support tyepdef'd arrays, so that's why it was >>> declared as a pointer, but yes, that should be fixed. I'll do that in >>> our copy, and it will go out with the 0.14.1 fixes (even though we >>> don't need it yet). There's still the case of, say, >>> >>> mpfr_init2(self._args[f(i)], self.domain.prec()) >>> >>> where f is a cdef int -> int function. Do we handle that? >> >> Sure. The problem isn't (any longer) that we *forget* to put things into a >> temp, the problem is that we try to put things into a temp now that we >> cannot store away. >> >> I've been dropping some cases in my latest commits where the temp copying >> mechanism was triggered needlessly. It's basically a matter of properly >> implementing is_simple() for an ExprNode in order to decide when a non-temp >> result is side-effect free. >> >> I'm still not sure if a coerce_to_owned() method would be worthwhile. As >> long as SimpleCallNode is the only place where this is actually needed, >> it's fine to leave the code there. Can anyone think of other places where >> the order of C value evaluation matters? Tuples and other container >> literals may qualify, but given that they use only Python values, I don't >> see it being a problem there. > > I'm not sure we handle the optimization of, e.g, "a in (x, y, z)" > There might be others as well. > > Fixing Sage is turning out to be non-trivial...there are many places > that assume mpz_t is (compatible with) a void*. We also have the > problem that Cython doesn't let you take the address of an array, as > it is a non-lvalue, but that's legal in C (and used in Sage).
There's another problem, assigning things to a temporary C++ class or struct can have side effects (as well as be inefficient). - Robert _______________________________________________ Cython-dev mailing list Cython-dev@codespeak.net http://codespeak.net/mailman/listinfo/cython-dev
