On 1 March 2018 at 18:54, Marc Glisse wrote: > On Thu, 1 Mar 2018, Tulio Magno Quites Machado Filho wrote: > >> In order to use the __float128 in C++ it's necessary to check if >> it is supported in libstdc++ (i.e. via _GLIBCXX_USE_FLOAT128) and if the >> compiler enabled its support too, e.g. -mfloat128 or -mno-float128. > > > Shouldn't we ensure that _GLIBCXX_USE_FLOAT128 is undefined instead?
Yes, a better approach might be to add this to libstdc++-v3/include/bits/c++config.h: #define _GLIBCXX_USE_FLOAT128 #if !defined(__FLOAT128__) && !defined(__SIZEOF_FLOAT128__) #undef _GLIBCXX_USE_FLOAT128 #endif Then change libstdc++-v3/acinclude.m4 so that instead of defining _GLIBCXX_USE_FLOAT128 it does: GLIBCXX_CONDITIONAL(ENABLE_FLOAT128, ...) and then have libstdc++-v3/include/Makefile modify <bits/c++config.h> based on that, setting _GLIBCXX_USE_FLOAT128 to 0 or 1
