c - 将字符串与 libusb 一起使用会导致段错误

Question

我使用 netbeans 和 gcc 进行编译。当我运行附加的代码时，出现错误: 运行完成；分段故障;核心已转储；实时:310ms；用户:40ms；系统:10ms

如果“char stringData”被注释掉，则不存在段错误。此外，如果删除 libusb_get_device_descriptor (以及随附的结构引用)，则不会出现段错误。

如果它在 Debug模式下运行，则会给出错误消息:

#error "Never use <bits/string_fortified.h> directly; include <string.h> instead."

我看不出它们如何相互影响。

#include <stdio.h>
#include <stdlib.h>
#include <libusb.h>
#define DATLENGTH 15

int main() {
    libusb_context *context;
    int i; 
    libusb_device **list;
    libusb_device *device;
    const struct libusb_version *libVersion;
    ssize_t numDev = 0;
    struct libusb_device_descriptor *dev_descriptor;
    struct libusb_config_descriptor *config;
    libusb_device_handle * dev_handle;
    char stringData[DATLENGTH];

    libusb_init(&context);


    libVersion = libusb_get_version();
    printf("Library Version: %i.%i.%i.%i\n", (int)libVersion->major, (int)libVersion->minor, (int)libVersion->micro, (int)libVersion->nano);

    numDev = libusb_get_device_list(context, &list);    
    if(numDev < 0){
        printf("Error %i\n", numDev);
        return -1;
    }
    else{
        printf("Number of devices: %i\n\n", numDev);
    }

    for(i=0;i<numDev;i++){    
        device = list[0];

        struct libusb_device_descriptor *dev_descriptor;

        libusb_get_device_descriptor(device, dev_descriptor);
        printf("Device #:  %i\n", i);
        printf("idVendor:  %04x\n", (dev_descriptor->idVendor & 0x0000FFFF));
        printf("idProduct: %04x\n", (dev_descriptor->idProduct & 0x0000FFFF));
        printf("Number of Configurations: %i\n", dev_descriptor->bNumConfigurations);
        libusb_open(device, &dev_handle);
        libusb_get_string_descriptor_ascii(dev_handle, dev_descriptor->iManufacturer, stringData, DATLENGTH);
        printf("Manufacturer ID: %s\n", stringData);        
        libusb_get_string_descriptor_ascii(dev_handle, dev_descriptor->iProduct, stringData, DATLENGTH);
        printf("Product ID: %s\n", stringData);       


        printf("\n");
        }

        libusb_free_device_list(list, 1); 

        libusb_exit(context);

    return (EXIT_SUCCESS);
}

Answer 1

您正在通过以下方式产生未定义的行为:

struct libusb_device_descriptor *dev_descriptor;
libusb_get_device_descriptor(device, dev_descriptor);

dev_descriptor 应该是指向 struct libusb_device_descriptor 的指针。但它是一个指向任何地方的指针，因为你从未初始化它。当 libusb_get_device_descriptor 尝试在结构中存储信息时，它将出现段错误或覆盖随机内存。

您应该将其更改为:

struct libusb_device_descriptor dev_descriptor;
libusb_get_device_descriptor(device, &dev_descriptor);

它实际上在堆栈上分配一个struct libusb_device_descriptor，然后传递该结构的地址。请注意，您必须将 dev_descriptor->field 始终更改为 dev_descriptor.field。