c - 在 C 中直接传递变量地址和传递指针(指向同一变量)之间的区别？

Question

我想知道为什么当使用语句 (*func_list_x32_x64[2]) (ptr_64); 调用函数 uint_x64_read 时不起作用(我没有得到任何警告或错误我的程序都会退出)，但在使用 (*func_list_x32_x64[2]) (&var_64);

时运行正常

func_ptr.h:

typedef enum {
    FUNC_PTR_SUCCESS = 0,
    FUNC_PTR_FAIL
} FUNC_PTR_STATUS;

typedef FUNC_PTR_STATUS (*func_ptr)(void *);

FUNC_PTR_STATUS uint_x32_read(void *);

FUNC_PTR_STATUS uint_x32_write(void *);

FUNC_PTR_STATUS uint_x64_read(void *);

FUNC_PTR_STATUS uint_x64_write(void *);

main.c 文件:

#include <stdio.h>
#include <stdint.h>

#include "func_ptr.h"

static func_ptr func_list_x32_x64[] = {
    (func_ptr) uint_x32_read,
    (func_ptr) uint_x32_write,
    (func_ptr) uint_x64_read,
    (func_ptr) uint_x64_write,
    NULL
};



void main() {
    uint8_t usr_option = 0;
    uint32_t var_32 = 0;
    uint32_t *ptr_32;
    uint64_t var_64 = 0;
    uint64_t *ptr_64;

    ptr_32 = &var_32;
    ptr_64 = &var_64;

    while (1) {
        printf("Enter option: ");
        scanf("%d", &usr_option);

        if(usr_option == 0)
            (*func_list_x32_x64[0]) ((void *)ptr_32);

        else if(usr_option == 1)
            (*func_list_x32_x64[1]) ((void *)ptr_32);

        else if(usr_option == 2) {
            (*func_list_x32_x64[2]) (ptr_64);
        }

        else if(usr_option == 3) {
            (*func_list_x32_x64[3]) (ptr_64);
        }

        else
            break;
    }
}

func_ptr.c:

#include <stdio.h>
#include <stdint.h> 


#include "func_ptr.h"


/**
 * @def Defines  #UINT_X32_ADDR_VAL as 2000
 */
#define         UINT_X32_ADDR_VAL       (2000u)

/**
 * @def Defines  #UINT_X64_ADDR_VAL as 4000
 */
#define         UINT_X64_ADDR_VAL       (4000u)



FUNC_PTR_STATUS uint_x32_read(void *data_32) {

    *(uint32_t *) data_32 = UINT_X32_ADDR_VAL;
    return FUNC_PTR_SUCCESS;

}



FUNC_PTR_STATUS uint_x64_read(void *data_64) {

    *(uint64_t *) data_64 = 45;
    return FUNC_PTR_SUCCESS;

}


FUNC_PTR_STATUS uint_x32_write(void *data_32) {

    printf("Val:        %d\n", *(uint32_t *) data_32);
    return FUNC_PTR_SUCCESS;

}


FUNC_PTR_STATUS uint_x64_write(void *data_64) {

    printf("Val:        %d\n", *(uint64_t *)data_64);
    return FUNC_PTR_SUCCESS;

}

编辑:添加了最少的可重现代码

Answer 1

您的代码存在导致未定义行为的错误。

scanf("%d", &usr_option);

printf("Val:        %d\n", *(uint32_t *)data_32);

printf("Val:        %d\n", *(uint64_t *)data_64);

void main()

应该是

#include <inttypes.h>

scanf("%" SCNu8, &usr_option);

printf("Val:        %" PRIu32 "\n", *(uint32_t *)data_32);

printf("Val:        %" PRIu64 "\n", *(uint64_t *)data_64);

int main(void)

始终启用并注意编译器的警告。 (我使用 -Wall -Wextra -pendatic 来表示 gcc。)