[cfe-dev] clang fails to compile gcc 4.8's <unordered_map>

[Howard Hinnant]

On May 31, 2012, at 5:18 AM, Chandler Carruth wrote:

> On Thu, May 31, 2012 at 2:15 AM, Sebastian Redl <sebastian.redl at getdesigned.at> wrote:
> On 31.05.2012 05:59, Nathan Ridge wrote:
> > The problem is that GCC uses the following alias template as class scope:
> >
> > template<typename _Pair>
> > using __is_convertible = std::is_convertible<_Pair, value_type>;
> >
> > but __is_convertible, I am guessing, is a compiler intrinsic in clang.
> >
> > Is either gcc or clang doing something wrong, or is it just a clash of implementations?
> It's a clash of implementations. We've had this before, but not with a
> new GCC version - only with old GCC versions.
> > What can be done to resolve this?
> >
> Since GCC 4.8 is not yet released, and Clang versions with the
> __is_convertible intrinsic are, the best solution would be to politely
> ask the libstdc++ maintainers to change this name.
> 
> Please let us know if you do / what the PR is for it? We're likely to hit this as well, and will want to track the progress of getting it resolved. 

This looks fixable on the clang side to me.  The clang intrinsic __is_convertible is currently undocumented:

http://clang.llvm.org/docs/LanguageExtensions.html#checking_type_traits

However we document __is_convertible_to

int main()
{
    static_assert(__is_convertible(int, long), "");
    static_assert(__is_convertible_to(int, long), "");
}

I imagine __is_convertible was left in to give time for things like libc++ to migrate to __is_convertible_to.  It has.  Why don't we just dump __is_convertible.

Howard