为什么我在函数中分配了指针内存,但它也是NULL？

Question

代码使我困惑.

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

void create_int(int *p)
{
    p = (int *) malloc(sizeof(int));
}

int main()
{
    int *p = NULL;

    create_int(p);

    assert(p != NULL);  /* failed. why? I've allocated memory for it. */

    return 0;
}

Answer 1

您没有从函数返回指针值.尝试:

void create_int(int **p) {
     *p = (int *) malloc(sizeof(int)); 
}  

int main() {
     int *p = NULL;      
     create_int(&p);
     assert(p != NULL);  /* failed. why? I've allocated memory for it. */
     return 0;
}