On 30/10/2024 17:00, Dimitry Andric via Cygwin wrote: > #include<string> > #include<cassert> > > constexpr bool foo() > { > std::string str2{"abcwe"}; > return str2.size()==5; > } > > static_assert(foo()); > > int main() > { > assert(foo()); > } Seems like _GLIBCXX_USE_CXX11_ABI is not defined by default. Csaba -- Life is complex, with real and imaginary parts.