的malloc（sizeof的（INT））VS的malloc（sizeof的为（int *））对为（int *）malloc的（的sizeof（int）的） [英] malloc(sizeof(int)) vs malloc(sizeof(int *)) vs (int *)malloc(sizeof(int))

问题描述

我承认，所有这三个具有不同的意义。但是，我不要将各自的应用，这些哪个特定实例理解。任何人都可以分享每一个这些的例子吗？谢谢你。

 的malloc（sizeof的（INT））VS的malloc（sizeof的为（int *））对为（int *）malloc的（的sizeof（int）的）
 

解决方案

的malloc（sizeof的（INT））意味着你离堆分配空间来存储 INT 。您保留的字节数为 INT 要求。 <击>这将返回你应该转换为价值为int * 。 （一个指​​向 INT ）如一些人所指出的，在C典型的做法是让隐式转换照顾这。

的malloc（sizeof的为（int *））意味着你离堆分配空间来存储一个指向 INT 。为指针，需要您预留的字节数。这将返回你应该强制转换为 A值INT ** 。 （A指针指向一个 INT ）

为（int *）malloc的（的sizeof（INT））是完全一样的第一个电话，但与结果明确铸造到一个指向 INT 。

请注意，在许多架构中，一个 INT 的大小为指针一样，所以这些会显得（错误地）是所有同样的事情。换句话说，你可以不小心做错事，并有导致code仍能正常工作。

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

解决方案

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

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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