是malloc()将分配的数组初始化为零吗? [英] Is malloc() initializing allocated array to zero?

问题描述

这是我正在使用的代码:

Here is the code I'm using:

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

int main() {
    int *arr;
    int sz = 100000;
    arr = (int *)malloc(sz * sizeof(int));

    int i;
    for (i = 0; i < sz; ++i) {
        if (arr[i] != 0) {
            printf("OK\n");
            break;
        }
    }

    free(arr);
    return 0;
}

程序不打印OK. malloc不应将分配的内存初始化为零.为什么会这样?

The program doesn't print OK. malloc isn't supposed to initialize the allocated memory to zero. Why is this happening?

推荐答案

malloc的手册页说:

malloc()函数分配大小字节并返回指向 分配的内存. 内存未初始化.如果大小为0， 然后malloc()返回NULL或可以 稍后将其成功传递给free().​​

The malloc() function allocates size bytes and returns a pointer to the allocated memory. The memory is not initialized. If size is 0, then malloc() returns either NULL, or a unique pointer value that can later be successfully passed to free().

因此，malloc()返回未初始化的内存，其内容是不确定的.

So, malloc() returns uninitialized memory, the contents of which is indeterminate.

 if (arr[i] != 0)

在您的程序中，您试图访问内存块的内容，该内存块被调用未定义的行为.

In your program, You have tried to access the content of a memory block, which is invoked undefined behavior.

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