c - 如何理解段错误？

Question

我第一次尝试在 C 中使用结构和指针。而且我真的不明白为什么我总是遇到段错误，即使程序编译得很好。我也对内存分配感到困惑。我们是否每次都在内存分配中使用强制转换？

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



#define HOW_MANY 7

char *names[HOW_MANY]= {"Adam", "James", "Matt", "Affleck", "Benedict", "Kayne",
    "Evans"};
int ages[HOW_MANY]= {22, 24, 46, 56, 21, 32, 30};

/* declare your struct for a person here */
typedef struct{
    char name[HOW_MANY];
    int age;
}person;


static void insert(person *people[], char *name, int age)
{
    static int nextfreeplace = 0;
    // Allocating memory here
    people = malloc(sizeof(person));

    if (people == NULL) {
        printf("Couldn't allocate memory");
        exit(-1);
    }

    strcpy((*people[nextfreeplace]).name,name);

    (*people[nextfreeplace]).age = age;

    nextfreeplace++;
}

int main(int argc, char **argv)
{
    person *people[HOW_MANY];

    for (int i = 0; i < HOW_MANY ; i++)
    {
        insert (people, names[i], ages[i]);
    }

    /* print the people array here*/
    for (int i = 0; i < HOW_MANY ; i++)
    {

        printf("The person's name is %s and the age is %d.\n",(*people[i]).name,(*people[i]).age);
    }

    for (int i = 0; i < HOW_MANY ; i++)
    {
        free(people[i]);
    }

    return 0;
}

这是分配内存的正确方法吗？

Answer 1

在您的 C 代码中保持相同的逻辑

调用 insert 提供指向您要分配内存的位置的指针，即 people 数组中指针位置的地址；在 main 函数 for 循环中:

insert (&people[i], names[i], ages[i]);

因此在插入，

static void insert(person **people, char *name, int age)
{
    *people = malloc(sizeof(person));

    if (*people == NULL) {
        printf("Couldn't allocate memory");
        exit(-1);
    }

    strcpy((*people)->name,name);

    (*people)->age = age;
}