malloc(sizeof(int)) vs malloc(sizeof(int *)) vs (int *)malloc(sizeof(int)) [英] malloc(sizeof(int)) vs malloc(sizeof(int *)) vs (int *)malloc(sizeof(int))

问题描述

我承认所有这三个都有不同的含义.但是，我不明白这些适用于哪些特定情况.任何人都可以为每一个分享一个例子吗?谢谢.

I acknowledge that all three of these have a different meaning. But, I don't understand on what particular instances would each of these apply. Can anyone share an example for each of these? Thank you.

       malloc(sizeof(int))
       malloc(sizeof(int *))
(int *)malloc(sizeof(int))

推荐答案

malloc(sizeof(int)) 意味着您正在分配堆外的空间来存储 int.您保留了 int 所需的字节数.这会返回一个您应该转换为 int * 的值.(指向 int 的指针.) 正如一些人所指出的，C 中的典型做法是让隐式转换来处理这一点.

malloc(sizeof(int)) means you are allocating space off the heap to store an int. You are reserving as many bytes as an int requires. This returns a value you should cast to int *. (A pointer to an int.) As some have noted, typical practice in C is to let implicit casting take care of this.

malloc(sizeof(int*)) 意味着您正在分配堆外的空间来存储指向 int 的指针.您保留了指针所需的字节数.这将返回一个您应该转换为 int ** 的值.(一个指向 int 的指针的指针.)

malloc(sizeof(int*)) means you are allocating space off the heap to store a pointer to an int. You are reserving as many bytes as a pointer requires. This returns a value you should cast to an int **. (A pointer to a pointer to an int.)

(int *)malloc(sizeof(int)) 与第一次调用完全相同，但结果显式转换为指向 int 的指针.

(int *)malloc(sizeof(int)) is exactly the same as the first call, but with the the result explicitly casted to a pointer to an int.

请注意，在许多体系结构上，int 与指针的大小相同，因此它们看起来(错误地)都是一样的.换句话说，您可能不小心做错了事，结果代码仍然可以工作.

Note that on many architectures, an int is the same size as a pointer, so these will seem (incorrectly) to be all the same thing. In other words, you can accidentally do the wrong thing and have the resulting code still work.

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