https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85672
--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> --- (In reply to Marc Glisse from comment #4) > (In reply to Jonathan Wakely from comment #3) > > Yes it woud have been broken by r259813 and this should fix it: > > I don't think that's sufficient: > - the same code is present in several files Only two. include/bits/std_abs.h and include/std/type_traits > - -Wsystem-headers -Wundef will warn That's the status quo. It would take a ton of effort to avoid -Wundef warnings in libstdc++ and that's not something I'm going to work on. > - it still leaves a weird situation where _GLIBCXX_USE_FLOAT128 may be 1, 0 > or undefined, instead of just 2 choices. Ah yes, good point. So we could either change include/Makefile.am to #undef it instead of setting it to 0, or do: --- a/libstdc++-v3/include/bits/c++config +++ b/libstdc++-v3/include/bits/c++config @@ -611,7 +611,10 @@ namespace std /* Define if __float128 is supported on this host. */ #define _GLIBCXX_USE_FLOAT128 -#if !defined(__FLOAT128__) && !defined(__SIZEOF_FLOAT128__) +#if _GLIBCXX_USE_FLOAT128 == 0 +#undef _GLIBCXX_USE_FLOAT128 +#endif +#elif !defined(__FLOAT128__) && !defined(__SIZEOF_FLOAT128__) #undef _GLIBCXX_USE_FLOAT128 #endif I think I'd prefer to change include/Makefile.am Then no changes to <bits/std_abs.h> and <type_traits> would be needed.
