Question

我遇到了以下问题：

标题文件“can_settings.h”：

#ifndef CAN_SETTINGS_H_
#define CAN_SETTINGS_H_

#ifdef __cplusplus
extern "C" {
#endif

#include "can.h"

extern const CAN_InitTypeDef can_initstruct;

extern const CAN_FilterInitTypeDef can_filter_acceptall;
extern CAN_FilterInitTypeDef can_filter_1;
extern CAN_FilterInitTypeDef can_filter_2;


#ifdef __cplusplus
}
#endif

#endif

源文件“can_settings.c”：

#include "can_settings.h"

const CAN_InitTypeDef can_initstruct = {
#ifdef SYSCLK_FREQ_72MHz
    // APB1_freq = 36 MHz
    /* .CAN_Prescaler = */ 24,
    /* .CAN_Mode = */ CAN_Mode_Normal,
    /* .CAN_SJW = */ CAN_SJW_1tq,
    /* .CAN_BS1 = */ CAN_BS1_8tq,
    /* .CAN_BS2 = */ CAN_BS2_3tq,
#elif defined SYSCLK_FREQ_24MHz
    // APB1_freq = 24 MHz
    /* .CAN_Prescaler = */ 16,
    /* .CAN_Mode = */ CAN_Mode_Normal,
    /* .CAN_SJW = */ CAN_SJW_1tq,
    /* .CAN_BS1 = */ CAN_BS1_8tq,
    /* .CAN_BS2 = */ CAN_BS2_3tq,
#endif
    /* .CAN_TTCM = */ DISABLE,
    /* .CAN_ABOM = */ DISABLE,
    /* .CAN_AWUM = */ DISABLE,
    /* .CAN_NART = */ DISABLE,
    /* .CAN_RFLM = */ DISABLE,
    /* .CAN_TXFP = */ ENABLE,
};

const CAN_FilterInitTypeDef can_filter_acceptall = {
    /* .CAN_FilterIdHigh = */ 0x0000,
    /* .CAN_FilterIdLow = */ 0x0000,
    /* .CAN_FilterMaskIdHigh = */ 0x0000,
    /* .CAN_FilterMaskIdLow = */ 0x0000,
    /* .CAN_FilterFIFOAssignment = */ 0,
    /* .CAN_FilterNumber = */ 0,
    /* .CAN_FilterMode = */ CAN_FilterMode_IdMask,
    /* .CAN_FilterScale = */ CAN_FilterScale_32bit,
    /* .CAN_FilterActivation = */ ENABLE
};

const CAN_FilterInitTypeDef can_filter_1 = {
        /* .CAN_FilterIdHigh = */ 0x0000,
        /* .CAN_FilterIdLow = */ CAN_ID_EXT,
        /* .CAN_FilterMaskIdHigh = */ 0x14FC << 3,
        /* .CAN_FilterMaskIdLow = */ CAN_ID_EXT,
        /* .CAN_FilterFIFOAssignment = */ 0,
        /* .CAN_FilterNumber = */ 0,
        /* .CAN_FilterMode = */ CAN_FilterMode_IdMask,
        /* .CAN_FilterScale = */ CAN_FilterScale_32bit,
        /* .CAN_FilterActivation = */ ENABLE
};

const CAN_FilterInitTypeDef can_filter_2 = {
        /* .CAN_FilterIdHigh = */ 0x0000,
        /* .CAN_FilterIdLow = */ CAN_ID_EXT,
        /* .CAN_FilterMaskIdHigh = */ 0x1400 << 3,
        /* .CAN_FilterMaskIdLow = */ CAN_ID_EXT,
        /* .CAN_FilterFIFOAssignment = */ 0,
        /* .CAN_FilterNumber = */ 1,
        /* .CAN_FilterMode = */ CAN_FilterMode_IdMask,
        /* .CAN_FilterScale = */ CAN_FilterScale_32bit,
        /* .CAN_FilterActivation = */ ENABLE
};

链接器返回未定义的引用'can_initstruct'can_filter_acceptall''can_filter_1''can_filter_2'... 文件can_settings。{c，h}构建为静态库，用于我的主应用程序（仅C）和我的CAN低级驱动程序（C ++）。所有静态库都是在我的低级驱动程序和主应用程序构建之前构建的。使用objdump我转储了静态CAN设置库，所有上述结构都列在.rodata部分中。我做错了什么......？

Answer 1

如果您正在使用GCC，请确保以正确的顺序指定库。有关详细说明，请参阅Why does the order in which libraries are linked sometimes cause errors in GCC?。

但是，如果您不想打扰库序列，只需指定序列两次而不是一次。应用于上述问题的公认答案，这意味着：

gcc prog.o libA.a libB.a libA.a libB.a -o prog.x

作为替代方案，请使用GCC的-Wl,--start-group ... -Wl,--end-group个标记（GCC: what are the --start-group and --end-group command line options?）。

Answer 2

好的，我明白了。您在GCC中指定目标文件和库的顺序非常重要！链接器搜索按它们出现的顺序进行思考，因此如果您有一个包含对库函数调用的源文件，则需要将它放在库之前，或者链接器不知道它必须解析它。我做错了......

感谢提示。

链接器：未定义的const C结构的引用，它位于静态lib中

2 个答案: