Fix bugs in sync library error handling

fnusb_open_subdevices checked for camera==NULL or res < 0 before
jumping to the failure case.  If camera was NULL but res was not
0, the function would return 0 indicating success.  This occurs
when a kinect is not plugged into the PC.  Forcing res to be
negative when the camera == NULL case allows the failure to open
a device to propagate through an application.

alloc_kinect in freenect_sync has a check for if freenect_open_device
fails, but the logic is incorrect.  freenect_open_device returns 0 on
success and < 0 on error, so adding a check to see if the return is
< 0 corrects detection of the failure case.

Signed-off-by: Rich Mattes <[email protected]>

Author: richmattes

src/usb_libusb10.c

@@ -465,6 +465,7 @@ FN_INTERNAL int fnusb_open_subdevices(freenect_device *dev, int index)
 	}
 
 	if (res < 0 || camera == NULL) {
+		res = -1;
 		goto failure;
 	}
 

wrappers/c_sync/libfreenect_sync.c

@@ -249,7 +249,7 @@ static int change_depth_format(sync_kinect_t *kinect, freenect_resolution res, f
 static sync_kinect_t *alloc_kinect(int index)
 {
 	sync_kinect_t *kinect = (sync_kinect_t*)malloc(sizeof(sync_kinect_t));
-	if (freenect_open_device(ctx, &kinect->dev, index)) {
+	if (freenect_open_device(ctx, &kinect->dev, index) < 0) {
 		free(kinect);
 		return NULL;
 	}