// Rewrite C.f(p) to
	//    func() {
	//            _cgo0 := p
	//            _cgoCheckPointer(_cgo0, nil)
	//            C.f(_cgo0)
	//    }()
	// Using a function literal like this lets us evaluate the
	// function arguments only once while doing pointer checks.
	// This is particularly useful when passing additional arguments
	// to _cgoCheckPointer, as done in checkIndex and checkAddr.
	//