4

我正在尝试使用libusb的 C 示例，并且在我尝试执行以下操作时一切正常：

libusb_device_descriptor descriptor;
int result = libusb_get_device_descriptor(usb_device, &descriptor);

编译器告诉我，在同一个libusb.h头文件中定义的某些元素，与我正在使用的其他 libusb 结构一样，没有声明。什么？

这是完整的代码：

#include <stdio.h>
#include <stdlib.h>
#include <libusb.h>

void printdev(libusb_device *usb_device);

/**
 * main
 */
int main(void) {
    puts("USB Test v0.0.1");

    libusb_device **usb_devices;
    libusb_context *usb_context = NULL;
    int result;
    result = libusb_init(&usb_context);
    ssize_t device_count;

    if (result < 0) {
        puts("USB initialization error!");
        return EXIT_FAILURE;
    }

    libusb_set_debug(usb_context, 1);
    device_count = libusb_get_device_list(usb_context, &usb_devices);

    if (device_count < 0) {
        puts("Unable to get USB device list!");
        return EXIT_FAILURE;
    }

    char message[24];
    sprintf(message, "%d USB Devices found", (int)device_count);
    puts(message);

    ssize_t i;
    for (i = 0; i < device_count; i++) {

    }

    libusb_free_device_list(usb_devices, 1);
    libusb_exit(usb_context);

    return EXIT_SUCCESS;
}

/**
 *
 */
void printdev(libusb_device *usb_device)
{
    libusb_device_descriptor descriptor;
    int result = libusb_get_device_descriptor(usb_device, &descriptor);

    if (result < 0) {
        puts("Failed to get device descriptor");
        return;
    }
}

如果我离开/注释掉 printdev 函数，代码编译，并且 main() 运行完美。但是为什么在 main 中使用了结构，比如定义了 libusb_device 和 libusb_context，但 libusb_device_descriptor 没有？

这是我的编译器输出：

23:18:07 **** Incremental Build of configuration debug for project usb_test ****
make all 
Building file: ../src/usb_test.c
Invoking: GCC C Compiler
gcc -I/usr/local/Cellar/libusb/1.0.9/include/libusb-1.0 -O0 -g3 -Wall -c -fmessage-length=0 -MMD -MP -MF"src/usb_test.d" -MT"src/usb_test.d" -o "src/usb_test.o" "../src/usb_test.c"
../src/usb_test.c: In function 'printdev':
../src/usb_test.c:52: error: 'libusb_device_descriptor' undeclared (first use in this function)
../src/usb_test.c:52: error: (Each undeclared identifier is reported only once
../src/usb_test.c:52: error: for each function it appears in.)
../src/usb_test.c:52: error: expected ';' before 'descriptor'
../src/usb_test.c:53: error: 'descriptor' undeclared (first use in this function)
make: *** [src/usb_test.o] Error 1

23:18:07 Build Finished (took 73ms)
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2 回答 2

7

我也研究过Libusb.h，而且libusb_config_descriptor不是类型定义的，所以你必须struct在libusb_config_descriptor.

于 2013-07-03T21:46:56.503 回答
3

libusb.h 中没有libusb_device_descriptor类型。

然而有一个struct libusb_device_descriptor

于 2013-07-03T21:35:57.290 回答