https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86533
--- Comment #3 from Jürgen Reuter <juergen.reuter at desy dot de> --- (In reply to Jonathan Wakely from comment #2) > My best guess is that you've messed up your GCC installation, because > _GLIBCXX20_CONSTEXPR should be defined in <bits/c++config.h> like so: > > #ifndef _GLIBCXX20_CONSTEXPR > # if __cplusplus > 201703L > # define _GLIBCXX20_CONSTEXPR constexpr > # else > # define _GLIBCXX20_CONSTEXPR > # endif > #endif > > If you have a headers using that macro then you should have the definition > of that macro too. > > Without preprocessed source there's no way to tell. Yes, indeed you are correct, the gcc build was screwed up. Sometimes when you do svn up on the gcc trunk, it compiles including bootstrap, but there was an incompatible change which you recognize later. The safer way is to always do a completely new build instead of just an update. Sorry for the false alarm.
