c - 引用数组指针中的值 (c)

Question

注意:已修​​复(底部说明)

出于某种原因，以下代码:

(*p_to_array)[m_p->number_of_match_positions] = (*p_to_temp_array)[k];

其中类型是:

match_pos_t (*p_to_array)[];
match_pos_t (*p_to_temp_array)[];
int number_of_match_positions;
int k;

顺便说一句:match_pos_t 是一个结构:

typedef struct match_pos
{
   char* string;
   long match_position;
}match_pos_t;

在“(”错误之前导致“语法错误”
如果将此代码替换为其他代码，则不会出现此错误。

有人可以告诉我为什么这会导致语法错误，以及我应该如何解决这个问题吗？

完整相关代码:

 typedef struct match_pos
{
    char* string;
    long match_position;
}match_pos_t;

typedef struct match_positions
{
    int number_of_match_positions;
    match_pos_t (*match_positions)[];
}match_positions_t;


typedef struct search_terms
{
    int number_of_search_terms;
    char* search_terms[];
}search_terms_t;

int BMH_string_search(char* search_string, char* file_string, match_positions_t* match_positions)
{
    return 0;
}



int determine_match_pos(search_terms_t** s_terms, char* file, match_positions_t* m_p)
{
    int i,j,k;
    match_positions_t* temp_m_p;

    i=0;
    /* s_terms is a null terminated data structure */
    while((*s_terms+i) != NULL)
    {
        for(j=0; j<(*s_terms+i)->number_of_search_terms; j++)
        {
            /* search for the string positions */
            BMH_string_search((*s_terms+i)->search_terms[j], file, temp_m_p);
            /* load out search positions into the return array */
            if(temp_m_p->number_of_match_positions != 0)
            {
                int total_m_ps = m_p->number_of_match_positions + temp_m_p->number_of_match_positions;
                m_p->match_positions = (match_pos_t (*)[])realloc(m_p->match_positions, sizeof(match_pos_t)*total_m_ps);

                k = 0;
                for( ; m_p->number_of_match_positions<total_m_ps; m_p->number_of_match_positions++)
                {
                    (*(m_p->match_positions))[m_p->number_of_match_positions] = (*(temp_m_p->match_positions))[k];
                    k++;
                }
            }
            free(temp_m_p);
        }
        i++;
    }
    return 0;
}

看来我真是太蠢了。在引用的值周围添加一组额外的括号即可解决问题(问题代码已通过修复进行更新):原文:

(m_p->*match_positions)[m_p->number_of_match_positions] = (temp_m_p->*match_positions)[k];

已修复:

(*(m_p->match_positions))[m_p->number_of_match_positions] = (*(temp_m_p->match_positions))[k];

不过，如果有人能解释为什么第一个错误而不是第二个错误，那么很高兴听到，因为我认为

object->*object2

与

相同

*(object->object2)

这是正确的还是我在这里遗漏了一些 c 定义？

Answer 1

I thought that object->*object2 was the same as *(object->object2)

不，在 C 语言中，. 和 -> 运算符期望标识符作为其右操作数。 C 中不存在 .* 和 ->* 运算符，您必须拼写出 *(structural.member) 或 *(structure_ptr->member) 手动。