C++ client leaks file descriptors on Windows

[lukeocamden]

Hello, it looks like the non-Windows implementations of MemoryMappedFile::createNew and MemoryMappedFile::mapExisting close file decsriptors by creating OnScopeExit objects immediately after a successful open.

However these OnScopeExit objects are missing from the Windows implementations of MemoryMappedFile::createNew and MemoryMappedFile::mapExisting so the file descriptors are leaked. This means that a client will hold the files open throughout its lifetime, preventing them from being cleaned up.

If you agree, do you think it makes sense to add them?

Thanks!

[mjpt777]

I've pushed a fix. Can you test if it works as expected for you now?

[lukeocamden]

Works perfectly - thank you!