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From: Michael Stevens (mail_at_[hidden])
Date: 2005-09-08 13:44:47
On Donnerstag 08 September 2005 20:44, Michael Stevens wrote:
> On Donnerstag 08 September 2005 20:43, Michael Stevens wrote:
> > On Donnerstag 08 September 2005 02:13, Paul C. Leopardi wrote:
> > > Hi Michael,
> > > Have you tried with the latest snapshot of gcc 4.1 ?
> >
> > Not yet. I have been wading through the stuff related to DR214 (bug
> > 19203). All rather heavy. Thanks for all the links.
> >
> > I have simplifed the test case which is effect by the changes. This
> > should be a good basis to compare result or work on GCC bug reports..
> >
> > // Effect of DR214 FIX (Bug 19203) on 2 simple function template cases
> >
> > template <class E>
> > class expression {
> > };
> >
> > // ef - deduction of E is via expression
> > template<class E>
> > void ef (expression<E> e);
> > template<class R, class E>
> > void ef (expression<E> e);
> >
> > // sf - deduction of S is simple
> > template<class S>
> > void sf (S s);
> > template<class R, class S>
> > void sf (S s);
> >
> > void test()
> > {
> > expression<int> a;
> > ef (a); // ok
> > ef<char> (a); // ok
> > ef<int> (a); // Ambiguous in 4.0.1 when R == E
> >
> > sf (a); // ok
> > sf<char> (a); // ok
> > sf<int> (a); // unambiguous
> > }
> >
> > For comparision intel-8.1 finds no ambiguities, vc-7.1 behaves as
> > gcc-4.0.1
> >
> > The result of the change is rather ogly. I believe there is nothing
> > fundementaly different in deducing the two forms of template parameters
> > expression<E>
> > OR
> > S
> >
> > Yet in the former case an ambiguity is possible and in the latter not!!
> > I don't see anything in DR214 that the two cases should be different.
> >
> > All the best,
> > Michael
> >
> > > PR 23513 may also be related. See
> > > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23513
> > >
> > > The change we are seeing may be related to C++ Standard Core Language
> > > Issue 402. See http://gcc.gnu.org/ml/gcc-patches/2005-03/msg02862.html
> > > and http://www.open-std.org/jtc1/sc22/WG21/docs/cwg_active.html
> > >
> > > 402. More on partial ordering of function templates
> > > Section: 14.5.5.2 temp.func.order
> > > Status: open
> > > Submitter: Nathan Sidwell
> > > Date: 7 Apr 2003
> > >
> > > I've tried with a few different versions and snapshots, with results:
> > >
> > > With gcc version 3.3.5 20050117 (prerelease) (SUSE Linux)
> > > your simple case compiles OK.
> > >
> > > Each of
> > > gcc version 4.0.1
> > > gcc version 4.0.2 20050825 (prerelease)
> > > gcc version 4.1.0 20050813 (experimental)
> > > gives an error message about an ambiguity:
> >
> > The latter probably has the FIX to bug 21799 in (dated 20050812) so I
> > assume this does not change anything for our situation.
> >
> > > Best regards, Paul Leopardi
--
___________________________________
Michael Stevens Systems Engineering
34128 Kassel, Germany
Phone/Fax: +49 561 5218038
Navigation Systems, Estimation and
Bayesian Filtering
http://bayesclasses.sf.net
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