表达式必须有指向结构或联合错误的指针

Question

t 变量从assigntime函数开始出现错误，说它必须有一个指向结构或联合类型的指针。指针是我的弱点，如果有人可以解释，而不仅仅是给我答案，我需要做些什么来解决这个问题，这将是最有帮助的！干杯。

//MY TIME C FILE
#include "my_time.h"
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>

struct my_time_int 
{
    int hour;
    int minute;
    int second;
};

void init_my_time(my_time *t)
{

    t=(my_time)malloc(sizeof(struct init_my_time*)); 
}

/*
 * Alter hour, minute, and second
 * Param h new value for hour
 * Param m new value for minute
 * Param s new value for second
*/
void assignTime(my_time *t, int h, int m, int s) 
{
    t->hour = h;
    t->minute = m;
    t->second = s;
}
//FOLLOWING CODE T VARIABLE HAS RED UNDERLINE ERROR SAYING EXPRESSION MUST HAVE POINTER TO STRUCT OR UNION>
char *toString(my_time t)
{ 
    char *r = (char *)malloc(12 * sizeof(char));

    if (t.hour >= 12) {
    if (t.hour == 12)
        sprintf(r, "%02d:%02d:%02d PM", 12, t.minute, t.second);
    else
        sprintf(r, "%02d:%02d:%02d PM", t.hour - 12, t.minute, t.second);
    }
    else {
        if (t.hour == 0)
        sprintf(r, "%02d:%02d:%02d AM", 12, t.minute, t.second);
        else
        sprintf(r, "%02d:%02d:%02d AM", t.hour, t.minute, t.second);
    }

    return r;

}

/*
 * Find printable form of time in 24 hour mode
 * Return String form of time in 24 hour mode for printing etc.
*/
char *toMilString(my_time t)
{ 
    char *s = (char *)malloc(9 * sizeof(char));

    sprintf(s, "%02d:%02d:%02d", t.hour, t.minute, t.second);
    return s;
}

/*
 * Find number of seconds elapsed since midnight
 * Return number of seconds elapsed since midnight as int
*/
int secsSinceMidnight(my_time t)
{
return t.second + (60 * t.minute) + (60 * 60 * t.hour);
}

头文件在这里：

#include <stdbool.h>

struct my_time_int;
typedef struct my_time_int *my_time;

void init_my_time(my_time *t);
void assignTime(my_time *t, int h, int m, int s);
void addTime(my_time t, double s);
char *toString(my_time t);
char *toMilString(my_time t);
bool equals(my_time this, my_time that);
bool my_timeIncHour(my_time *t);
bool my_timeIncMinute(my_time *t);
bool my_timeIncSecond(my_time *t);

Answer 1

尝试malloc(sizeof(struct my_time_int));而不是malloc(sizeof(struct init_my_time*));您正在为指向init_my_time而不是 for 的指针分配内存my_time。

t是一个指向 a 的指针my_time_int，这意味着您需要分配足够的内存来存储my_time_int对象。指针本身存储在堆栈中，因此不需要为其分配内存。

void init_my_time(my_time *t)
{
    *t=(my_time)malloc(sizeof(struct my_time_int)); 
}