On 21 Oct 2016, at 17:07, Willem Jan Withagen <w...@digiware.nl> wrote: > > On 21-10-2016 15:09, Willem Jan Withagen wrote: >> Hi, >> >> All this Ceph stuff finally used to compile under FreeBSD. >> And all testss completed correctly. >> >> But somewhere in the Ceph-tree there was a lot of template and trait >> code added/replaced. >> Problem is that this compiles under GCC, but Clang throws an error. It >> looks like it cannot select types of automagic conversion. >> >> But this template/trait stuff is too much for me to wrap my head around. >> I'm reading up a lot, but that does not yet get me anywhere. >> >> So I was wondering if anybody with more C++ knowledge would like to >> assist and give some clues as to how to fix this. >> >> The error report is at: >> >> http://cephdev.digiware.nl:8180/jenkins/job/ceph-freebsd/39/consoleFull >> >> And the ceph code can be found at: >> https://github.com/ceph/ceph > > Oke, the preson responsable for the change helped to figure it out, and > it looks like the following diff helps > > diff --git a/src/include/denc.h b/src/include/denc.h > index 59f7686..caa095b 100644 > --- a/src/include/denc.h > +++ b/src/include/denc.h > @@ -722,7 +722,7 @@ struct denc_traits< > template<typename T> > struct denc_traits< > std::vector<T>, > - typename std::enable_if<denc_traits<T>::supported>::type> { > + typename std::enable_if<denc_traits<T>::supported != 0>::type> { > typedef denc_traits<T> traits; > > enum { supported = true }; > @@ -831,7 +831,7 @@ struct denc_traits< > template<typename T> > struct denc_traits< > std::set<T>, > - typename std::enable_if<denc_traits<T>::supported>::type> { > + typename std::enable_if<denc_traits<T>::supported != 0>::type> { > typedef denc_traits<T> traits; > > enum { supported = true }; > > And the conclusion is that std::enable_if<> does not always like it when > the value is 'int'. > the definition of supported is: > struct denc_traits { > enum { supported = 0 }; > enum { featured = false }; > enum { bounded = false }; > }; > > and values can range 0..2. > > So is this a GCC liberalization, or is Clang here to picky?
It's hard to say without the full source code and a reproducer, but I'd say that enable_if has a bool as the first template argument, so it can't match an int by default. Maybe libstdc++ has a variant with an int as the first template argument, but I haven't looked. -Dimitry
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