八进制常数误差(libusb)

我正在运行Ubuntu 12.04编译一个c++文件，其中包含以下代码

#include <iostream>
#include <libusb-1.0/libusb.h>
using namespace std;
int main(){
    //pointer to pointer of device used to retrieve a list of devices
    libusb_device **devs;
    libusb_device_handle *dev_handle; //a device handle
    libusb_context *ctx = NULL; //A LIBUSB session
    int r;// for return values
    ssize_t cnt; //holding number of devices in list
    r = libusb_init(&ctx); // initialize the library for the session we just declared
    if(r < 0){
        cout <<"init error "<<r<< endl;
        return 1;
    }
    libusb_set_debug(ctx, 3); // set verbosity level to 3, as suggested in the documentation
    cnt = libusb_get_device_list(ctx, &devs); //get the list of devices
    if (cnt < 0) {
        cout <<"Get Device Error "<< endl; // there was an error
        return 1;
    }
    cout << cnt <<" Device in list " << endl;
    //dev_handle = libusb_open_device_with_vid_pid(ctx, 0951, 1689); // these are vendor id and product id   //simon's usb(duracell)1516:1213
    dev_handle = libusb_open_device_with_vid_pid(ctx, 0951, 1689); //these are vendorID and productID I found for my usb device
    if (dev_handle == NULL){
        cout <<"Cannot open device "<< endl;
    }else{
        cout << "Device opened" << endl;
    }
    libusb_free_device_list(devs, 1);// free the list unref the devices in it
    unsigned char *data = new unsigned char[4];//data to write
    data[0] = 'a'; data[1] = 'b'; data[2] = 'c'; data[3] = 'd';//some dummy values
    int actual; //used to find how many bytes were written
    if (libusb_kernel_driver_active(dev_handle, 0) == 1){// findout if kernal driver attached
        cout << "Kernal Driver Active" << endl;
        if (libusb_detach_kernel_driver(dev_handle, 0) == 0 ){  //detach it
            cout<< "Kernal Driver Detached" << endl;
        }
    }
    r = libusb_claim_interface(dev_handle, 0);// claim interface 0 (the first) of devices
    if(r < 0){
        cout <<"Cannot claim interface "<<endl;
        return 1;
    }
    cout <<"Claimed interface "<<endl;
    cout<<"data->"<<data<<"<-"<<endl; // just to see the data we want to write : abcd
    cout<<"Writing data..."<<endl;
    r = libusb_bulk_transfer(dev_handle, (2 | LIBUSB_ENDPOINT_OUT), data, 4, &actual, 0);//my device's out endpoint was 2, found withe trial - the device had two endpoints: 2 and 129
    if(r == 0 && actual == 4){  // we wrote 4 bytes successfully
        cout<<"Writing successfull"<<endl;
    }else{
        cout<<"write error"<<endl;
    }
    r = libusb_release_interface(dev_handle, 0); // release the claimed interface
    if(r!=0) {
        cout<<"Cannot Release Interface"<<endl;
        return 1;
    }
    cout<<"Released interface"<<endl;
    libusb_close(dev_handle); // close the device we opened
    libusb_exit(ctx); // need to be called to end the
    delete[] data;// delete the allocated memory for data
    return 0;
}

但是当我使用以下命令行编译上述代码时(这些是我的usb的产品id和供应商id)

dev_handle = libusb_open_device_with_vid_pid(ctx, 0951, 1689);

编译器抛出以下错误

transfer_data_libusb.cpp:30:55: error: invalid digit "9" in octal constant

有人建议我去掉前导零ie(用"951"代替"0951")但是当我这样做时，文件编译成功，但是当我运行编译后的版本时，会抛出以下错误

7 Device in list 
Cannot open device 
Segmentation fault (core dumped)

不知道我该怎么做，你能帮我一下吗?顺便说一下，我用下面的命令来编译上面的代码

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

非常感谢您的宝贵时间