Windows: use native thread API instead of pthread

[vtorri]

On Windows, mingw project provides winpthread forPOSIX thread interface. But according to the devs:

• winpthread was written for the Windows port of gcc
• winpthread is slower than native API (because of all the code needed to have a POSIX interface).

would it be possible to have such implementation (supported versions of Windows : >= Vista, as for example, conditions are implemented since Vista) ?

thank you

[Jovasa]

We have our own wrapper for c++ threads API here https://github.com/ultravideo/kvazaar/tree/master/src/threadwrapper that is used by the MSVC build, would using it also in mingw suffice? It should be fairly simple to enable on CMakeLists
This without getopt.c

kvazaar/CMakeLists.txt

Lines 212 to 214 in 9eed4c3

	if(MSVC)
	list(APPEND CLI_SOURCES ${CMAKE_CURRENT_SOURCE_DIR}/src/extras/getopt.c ${CMAKE_CURRENT_SOURCE_DIR}/src/threadwrapper/src/pthread.cpp ${CMAKE_CURRENT_SOURCE_DIR}/src/threadwrapper/src/semaphore.cpp)
	endif()

and this

kvazaar/CMakeLists.txt

Line 224 in 9eed4c3

target_include_directories(kvazaar PUBLIC src/threadwrapper/include)

should be included with MSYS/MINGW

and these excluded

kvazaar/CMakeLists.txt

Lines 243 to 245 in 9eed4c3

	set(THREADS_PREFER_PTHREAD_FLAG ON)
	find_package(Threads REQUIRED)
	target_link_libraries(kvazaar PUBLIC Threads::Threads)

At least in theory it should work, though I haven't tested it.

[vtorri]

ok, you use the c++11 thread API. That means:

• with unix : usage of pthread
• with cl.exe (Windows compiler) : usage of native Win32 API
• with mingw : usage of winpthread, wich is a port of pthread on Windows as I said

so the current implementation will work (i can see that libkvazaar-7.dll is linked against libwinpthread.dll with mingw). It's just that i would have prefered a native implementation with mingw. But it is some work

[Jovasa]

Unfortunately I won't have time to work on this but if you want to do it I can accept a pull request.

[vtorri]

if i have time, i'll look at it