内存分配的问题 [英] Memory Allocation Problem

问题描述

这个问题被问了写轮面试的：

This question was asked in the written round of a job interview:

 #include<alloc.h>
 #define MAXROW 3
 #define MAXCOL 4

 main()
  {
    int (*p)[MAXCOL];
     p = (int (*)[MAXCOL]) malloc(MAXROW*(sizeof(*p)));
  }

多少字节的过程中被分配？

How many bytes are allocated in the process?

说实话，我并没有回答这个问题。我不明白分配到 P 。

To be honest, I did not answer the question. I did not understand the assignment to p.

谁能给我解释一下什么是答案，以及如何推导？

Can anybody explain me what would be the answer and how it can be deduced?

推荐答案

这是依赖于平台。

INT（* P）MAXCOL]; 声明了一个指向整数数组元素MAXCOL宽（当然是MAXCOL 4在这种情况下）。因此，这个指针的一个元素是 4 * sizeof的（INT）目标平台上。

int (*p)[MAXCOL]; declares an pointer to an array of integers MAXCOL elements wide (MAXCOL of course is 4 in this case). One element of this pointer is therefore 4*sizeof(int) on the target platform.

的的malloc 语句分配的内存缓冲区的MaxRow时间包含在P.因此，类型，总共的MaxRow规模* MAXCOL整数分配。字节的实际数量将取决于目标平台上。

The malloc statement allocates a memory buffer MAXROW times the size of the type contained in P. Therefore, in total, MAXROW*MAXCOL integers are allocated. The actual number of bytes will depend on the target platform.

此外，还有C运行时使用的可能是更多的内存（如malloc的内部bookeeping，以及前主被称为其中发生的各种进程初始化位），这也完全依赖于平台。

Also, there's probably additional memory used by the C runtime (as internal bookeeping in malloc, as well as the various process initialization bits which happen before main is called), which is also completely platform dependant.

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