build errors libusb

[toomanyhobbies-dev]

On Ubuntu 20.04.2 LTS, the following additional steps were required build and test the library.

Build Issues

Per README.md the instructions indicate to install libusb-1.0.0. I installed libusb-1.0.0-dev, however I received the following errors when attempting to compile:

nu/libGL.so -lpthread   
/usr/bin/ld: ../libcmmk/out/libcmmk.so: undefined reference to `libusb_get_device_descriptor'
/usr/bin/ld: ../libcmmk/out/libcmmk.so: undefined reference to `libusb_open_device_with_vid_pid'
/usr/bin/ld: ../libcmmk/out/libcmmk.so: undefined reference to `libusb_close'
/usr/bin/ld: ../libcmmk/out/libcmmk.so: undefined reference to `libusb_init'
/usr/bin/ld: ../libcmmk/out/libcmmk.so: undefined reference to `libusb_detach_kernel_driver'
/usr/bin/ld: ../libcmmk/out/libcmmk.so: undefined reference to `libusb_kernel_driver_active'
/usr/bin/ld: ../libcmmk/out/libcmmk.so: undefined reference to `libusb_attach_kernel_driver'
/usr/bin/ld: ../libcmmk/out/libcmmk.so: undefined reference to `libusb_free_device_list'
/usr/bin/ld: ../libcmmk/out/libcmmk.so: undefined reference to `libusb_claim_interface'
/usr/bin/ld: ../libcmmk/out/libcmmk.so: undefined reference to `libusb_interrupt_transfer'
/usr/bin/ld: ../libcmmk/out/libcmmk.so: undefined reference to `libusb_get_device_list'
/usr/bin/ld: ../libcmmk/out/libcmmk.so: undefined reference to `libusb_exit'
/usr/bin/ld: ../libcmmk/out/libcmmk.so: undefined reference to `libusb_release_interface'
collect2: error: ld returned 1 exit status
make[1]: *** [Makefile:172: cmmk_ctrl] Error 1
make[1]: Leaving directory '/home/tdo/Projects/cmmk_ctrl/build'
make: *** [Makefile:11: cmmk_ctrl] Error 2

I resolved the error by install the libusb-dev package which included resulted in the following packages being installed:

ii  libusb-0.1-4:amd64     2:0.1.12-32      amd64        userspace USB programming library
ii  libusb-1.0-0:amd64     2:1.0.23-2build1 amd64        userspace USB programming library
ii  libusb-1.0-0-dev:amd64 2:1.0.23-2build1 amd64        userspace USB programming library development files
ii  libusb-1.0-doc         2:1.0.23-2build1 all          documentation for userspace USB programming
ii  libusb-dev             2:0.1.12-32      amd64        userspace USB programming library development files

I suspect, that the references are due to depreciated functions in libusb-1.0 that were a part of libusb-0.1. For an update - I suggest the documentation be updated to reference libusb-dev or to update the code to only rely on libusb-0.1-4.