如何获得指针指向的内存大小? [英] How to get the size of memory pointed by a pointer?

问题描述

我目前正在NUMA机器上工作.我正在使用numa_free释放分配的内存.但是，与free不同，numa_free需要知道要释放多少字节.有没有办法知道一个指针所指向的字节数却没有找到它?

I am currently working on a NUMA machine. I am using numa_free to free my allocated memory. However, unlike free, numa_free needs to know how many bytes are to be freed. Is there any way to know that how many bytes are pointed to by a pointer without tracing it out?

推荐答案

无法使用基础API获取内存大小.在分配某处时，您必须记住大小.例如，您可以编写自己的分配器，该分配器分配4个额外的字节，存储在缓冲区的前4个字节中，在释放期间，您可以从中读取缓冲区的大小:

There is no way to obtain memory size using underlying API. You must remember size during the allocation somewhere. For Example, You may write your own allocator, that allocates 4 extra bytes, stores in first 4 bytes size of buffer, and during deallocation you can read size of buffer from it:

void *my_alloc(size_t size)
{
    void *buff = numa_alloc_local( size + sizeof(size_t) );
    if (buff == 0) return 0;

    *(size_t *)buff = size;
    return buff + sizeof(size_t);
}

void my_free(void *buf)
{
    numa_free(buf - sizeof(size_t), *(size_t *)(buf - sizeof(size_t)));
}

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