https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115960
--- Comment #6 from Andrew Pinski <pinskia at gcc dot gnu.org> --- (In reply to Noah Williams from comment #5) > It isn't? The library I was trying to compile included the "optional" > header, and I had looked it up and found it was part of C++ 17, so I thought > it was part of the standard. std::optional is part of C++17 but Optional is not. LLVM had its own Optional class which basically implemented what was included in C++17 before they wrote LLVM in C++17. This is the whole confusing thing with their code is that LLVM is compiled as C++17 but sometimes uses their own Optional class and sometimes std::optional. But again this is not GCC related issue and should be discussed in LLVM's developmental forms instead.
