Standard C++11 threading classes implementation, which are currently still missing on MinGW GCC.
This implementation should work with Windows XP (regardless of service pack), or newer. Since Vista, Windows has native condition variables, but we do not rely on them, to keep compatibility with Windows XP.
This is a header-only library. To use, just include the corresponding mingw.xxx.h file, where xxx would be the name of the standard header that you would normally include. For additional mutex helper classes, such as std::scoped_guard or std::unique_lock, you need to include <mutex> before including mingw.mutex.h
This code has been tested to work with MinGW-w64 5.3.0, but should work with any other MinGW version that has the std threading classes missing, has C++11 support for lambda functions, variadic templates, and has working mutex helper classes in <mutex>.
Switching from the win32-pthread based implemetation
It seems that recent versions of mingw-w64 include a win32 port of pthreads, and have the std::thread, std::mutex etc classes implemented and working, based on that compatibility layer. This is a somewhat heavier implementation, as it brings a not very thin abstraction layer. So you may still want to use this implementation for efficiency purposes. Unfortunately you can't use it standalone and independent of the system <mutex> header, as it relies on it for std::unique_lock and other non-trivial utility classes. In that case you will need to edit the c++-config.h file of your MinGW setup and comment out the definition of _GLIBCXX_HAS_GTHREADS. This will cause the system headers to not define the actual thread, mutex, etc classes, but still define the necessary utility classes.
Why MinGW has no threading classes
It seems that for cross-platform threading implementation, the GCC standard library relies on the gthreads/pthreads library. If this library is not available, as is the case with MinGW, the std::thread, std::mutex, std::condition_variable are not defined. However, higher-level mutex helper classes are still defined in <mutex> and are usable. Hence, this implementation does not re-define them, and to use these helpers, you should include <mutex> as well, as explained in the usage section.