为什么不free(p)将p设置为NULL? [英] Why doesn't free(p) set p to NULL?

问题描述

为什么不能成为free()的标准行为?

Any reasons why this can not be standard behavior of free()?

指向同一对象的多个指针:

multiple pointers pointing to the same object:

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

void safefree(void*& p)
{
    free(p); p = NULL;
}

int main()
{
    int *p = (int *)malloc(sizeof(int));
    *p = 1234;
    int*& p2 = p;
    printf("p=%p p2=%p\n", p, p2);
    safefree((void*&)p2);
    printf("p=%p p2=%p\n", p, p2);
    safefree((void*&)p); // safe

    return 0;
}

从malloc进行

分配需要从void*

反之亦然:

safefree()要求强制转换为void*&(参考)

safefree() demands cast to void*& (reference)

推荐答案

如果这样做，则必须将指针传递给该函数的指针:

If it did, you would have to pass a pointer to a pointer to the function:

int * p = malloc( sizeof( int ));
free( & p );

我相信很多人都会出错.

which I'm sure many people would get wrong.

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