Making code involving syscalls testable in peertracker

[jameshiew]

• Version: v1.11.1
• Platform: N/A
• Subsystem: Windows syscalls in peertracker

Relates to #5749

Some code which makes direct syscalls is hard to test, e.g. compareObjectHandles which behaves differently on different Windows systems.

spire/pkg/common/peertracker/npipe_windows.go

Lines 67 to 76 in 802ea39

	func compareObjectHandles(firstHandle, secondHandle windows.Handle) error {
	if procCompareObjectHandlesErr != nil {
	return procCompareObjectHandlesErr
	}
	r1, _, e1 := syscall.SyscallN(procCompareObjectHandles.Addr(), uintptr(firstHandle), uintptr(secondHandle))
	if r1 == 0 {
	return e1
	}
	return nil
	}

One way might be to change these sorts of funcs into methods on a type that allows swapping out syscall.SyscallN and other currently global variables for something that can be overridden at test time, so that surrounding logic can be tested (example in #5749 (comment))

func (s syscaller) compareObjectHandles(firstHandle, secondHandle windows.Handle) error {
	if s.procCompareObjectHandlesErr != nil {
		return s.procCompareObjectHandlesErr
	}
	r1, _, e1 := s.syscallN(*s.procCompareObjectHandlesAddr, uintptr(firstHandle), uintptr(secondHandle))
	if r1 == 0 {
		return e1
	}
	return nil
}