@eht16 what version of g++/libstdc++ is used for windows, nowhere does the version get printed in configure or build, grrrr? The build is now running but failing when it can't find `std::mutex` (and yes Neil did `#include <mutex>` https://github.com/geany/geany/blob/e4feb5cab6e4e2b878fae7be7cbd20ceb729fedf...). That is C++11 AFAIK so not sure why it fails unless you are using an ancient version of g++. I suspect Scintilla (not just Lexilla) now needs a real C++17 toolset.