On Wed, 2 Nov 2011 19:41:30 -0700 Guido van Rossum <gu...@python.org> wrote: > Apparently Macports is still using a buggy compiler.
If I understand things correctly, this is technically not a buggy compiler but Python making optimistic assumptions about the C standard. (from issue11149: "clang (as with gcc 4.x) assumes signed integer overflow is undefined. But Python depends on the fact that signed integer overflow wraps") I'd happily call that a buggy C standard, though :-) Regards Antoine. > I reported a > similar issue before and got this reply from Ned Delly: > > """ > Thanks for the pointer. That looks like a duplicate of Issue11149 (and > Issue12701). Another manifestation of this was reported in Issue13061 > which also originated from MacPorts. I'll remind them that the > configure change is likely needed for all Pythons. It's still safest to > stick with good old gcc-4.2 on OS X at the moment. > """ > > (Those issues are on bugs.python.org.) > > --Guido > > On Wed, Nov 2, 2011 at 7:32 PM, Derek Shockey <derek.shoc...@gmail.com> wrote: > > I just found an unexpected behavior and I'm wondering if it is a bug. > > In my 2.7.2 interpreter on OS X, built and installed via MacPorts, it > > appears that integers are not correctly overflowing into longs and > > instead are yielding bizarre results. I can only reproduce this when > > using the exponent operator with two ints (declaring either operand > > explicitly as long prevents the behavior). > > > >>>> 2**100 > > 0 > >>>> 2**100L > > 1267650600228229401496703205376L > > > >>>> 20**20 > > -2101438300051996672 > >>>> 20L**20 > > 104857600000000000000000000L > > > >>>> 10**20 > > 7766279631452241920 > >>>> 10L**20L > > 100000000000000000000L > > > > To confirm I'm not crazy, I tried in the 2.7.1 and 2.6.7 installations > > included in OS X 10.7, and also a 2.7.2+ (not sure what the + is) on > > an Ubuntu machine and didn't see this behavior. This looks like some > > kind of truncation error, but I don't know much about the internals of > > Python and have no idea what's going on. I assume since it's only in > > my MacPorts installation, it must be build configuration issue that is > > specific to OS X, perhaps only 10.7, or MacPorts. > > > > Am I doing something wrong, and is there a way to fix it before I > > compile? I could find any references to this problem as a known issue. > > > > Thanks, > > Derek > > _______________________________________________ > > Python-Dev mailing list > > Python-Dev@python.org > > http://mail.python.org/mailman/listinfo/python-dev > > Unsubscribe: > > http://mail.python.org/mailman/options/python-dev/guido%40python.org > > > > > > -- > --Guido van Rossum (python.org/~guido) _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
