You seem to have some terminology problems here. Windows VirtualAlloc may "commit" memory but that does not mean it actually reserves physical pages [1]. That always happens only when the memory is accessed. On the other hand, MSVC's malloc() probably uses HeapAlloc(), which in turn uses VirtualAlloc(). I don't think there are any fundamental differences between Linux and Windows here.

[1] "Actual physical pages are not allocated unless/until the virtual addresses are actually accessed." http://msdn.microsoft.com/en-us/library/windows/desktop/aa36...