This page documents some notable differences between the platforms that libusbp supports that can affect the library's behavior.
On Linux, a udev rule is typically needed in order to grant permissions for non-root users to directly access USB devices. The simplest way to do this would be to add a file named usb.rules in the directory /etc/udev/rules.d with the following contents, which grants all users permission to access all USB devices:
SUBSYSTEM=="usb", MODE="0666"
On Linux, you can have multiple simultaneous handles open to the same generic interface of a device. On Windows and macOS, this is not possible, and you will get an error with the code LIBUSBP_ERROR_ACCESS_DENIED when trying to open the second handle with libusbp_generic_handle_open.
On macOS, you cannot specify a timeout for an interrupt IN endpoint. Doing so will result in the following error when you try to read from the endpoint:
Failed to read from pipe. (iokit/common) invalid argument. Error code 0xe00002c2.
On Windows, calling libusbp_device_get_serial_number on a device that does not actually have a serial number will retrieve some other type of identifier that contains andpersands (&) and numbers. On other platforms, an error will be returned with the code LIBUSBP_ERROR_NO_SERIAL_NUMBER.
On Linux, a synchronous (blocking) USB transfer cannot be interrupted by pressing Ctrl+C. Other signals will probably not work either.
Performing control transfers that are directed to a specific interface might not work correctly on all systems, especially if the device is a composite device and the interface you are connected to is not the one addressed in your control transfer. For example, see this message from the libusb mailing list.