_GLIBCXX14_CONSTEXPR

[Jonathan Wakely]

On 4 January 2015 at 19:41, Tim Prince wrote:
> Yes, sorting out -E shows that some of these .h files are updating only
> in a newer directory which comes later on the search path than the
> directory which was used a month ago.    So the advice about clean
> environment includes cleaning out the old installation directories.

That doesn't sound right to me.

None of the relevant libstdc++ files should have moved location, at
least not since the include path changed from include/c++/4.9.0
 to include/c++/5.0.0, and no other directory containing a c++config.h
should be in the search path.

Which files were you seeing duplicated in "the directory used a month
ago" and what directory was that?