An invalid pointer triggers a runtime failure when passed as argument in

Go1.7:
runtime: bad pointer in frame
github.com/kylelemons/gousb/usb.(*fakeLibusb).open at 0xc420045ce0: 0x1
fatal error: invalid stack pointer

Use an arbitrary C-allocated pointer instead.

usb/fakelibusb_test.go

@@ -19,7 +19,6 @@ import (
 	"fmt"
 	"sync"
 	"time"
-	"unsafe"
 )
 
 var (
@@ -302,12 +301,12 @@ func newFakeLibusb() *fakeLibusb {
 		handles:     make(map[*libusbDevHandle]*libusbDevice),
 		claims:      make(map[*libusbDevice]map[uint8]bool),
 	}
-	for i, d := range fakeDevices {
+	for _, d := range fakeDevices {
 		// libusb does not export a way to allocate a new libusb_device struct
 		// without using the full USB stack. Since the fake library uses the
-		// libusbDevice only as an identifier, use arbitrary numbers pretending
+		// libusbDevice only as an identifier, use an arbitrary unique pointer.
-		// to be pointers. The contents of these pointers is never accessed.
+		// The contents of these pointers is never accessed.
-		fl.fakeDevices[(*libusbDevice)(unsafe.Pointer(uintptr(i)))] = &fakeDevice{
+		fl.fakeDevices[(*libusbDevice)(newCPointer())] = &fakeDevice{
 			desc: d,
 			alt:  0,
 		}

usb/libusb.go

@@ -421,7 +421,11 @@ func xfer_callback(cptr unsafe.Pointer) {
 	close(ch)
 }
 
-// for benchmarking
+// for benchmarking and testing
 func libusbSetDebug(c *libusbContext, lvl int) {
 	C.libusb_set_debug((*C.libusb_context)(c), C.int(lvl))
 }
+
+func newCPointer() unsafe.Pointer {
+	return unsafe.Pointer(C.malloc(1))
+}