LIBUSB compile error

Question

I am running c/c++ on Ubuntu and trying to compile the following code

#include <cassert>
#include <cstdio>
#include <libusb-1.0/libusb.h>

int main() {
    libusb_context *context = NULL;
    libusb_device **list = NULL;
    int rc = 0;
    ssize_t count = 0;

    rc = libusb_init(&context);
    assert(rc == 0);

    count = libusb_get_device_list(context, &list);
    assert(count > 0);

    for (size_t idx = 0; idx < count; ++idx) {
        libusb_device *device = list[idx];
        libusb_device_descriptor desc = {0};

        rc = libusb_get_device_descriptor(device, &desc);
        assert(rc == 0);

        printf("Vendor:Device = %04x:%04x\n", desc.idVendor, desc.idProduct);
    }
}

I get the following error when after I compile my code. Don't have any idea what should I do?

/tmp/ccESLZ0k.o: In function `main':
libusbtest.cpp:(.text+0x2f): undefined reference to `libusb_init'
libusbtest.cpp:(.text+0x64): undefined reference to `libusb_get_device_list'
libusbtest.cpp:(.text+0xd4): undefined reference to `libusb_get_device_descriptor'
collect2: ld returned 1 exit status

I am a novice user of Ubuntu, c/c++ and libusb, so any help would be appreciated

Thanks

Answer 1

This is a linker error.

You need to tell the linker to include libusb , which contains these referenced functions (eg -lusb ) and also where it is (eg -L/usr/local/lib ). Actual values will depend on your installation.

As Avidanborisov's answer highlights, you can use the pkg-config tool to determine the linker flags. On my system this looks like:

% pkg-config --libs libusb-1.0                                    
-L/usr/local/Cellar/libusb/1.0.9/lib -lusb-1.0

You can feed this information directly to gcc :

% g++ libusbtest.cpp $(pkg-config --libs libusb-1.0) -o libusbtest

Assuming all goes according to plan, you should now have an executable file libusbtest in your current working directory. You can run it like this:

% ./libusbtest                                                    
Vendor:Device = 05ac:8006
Vendor:Device = 05ac:8006
Vendor:Device = 05ac:8005
Vendor:Device = 05ac:8005
Vendor:Device = 05ac:850a
Vendor:Device = 05ac:023f
Vendor:Device = 05ac:8403

Answer 2

使用pkg-config获取该库所需的编译器标志：

g++ libusbtest.cpp `pkg-config --libs libusb` -o libusbtest