如何延迟分配归零内存？

据我了解，我必须做出选择calloc，这将分配归零内存，并且malloc，可以按需分配内存。

是否有一个函数结合了这两个属性？或许可以直接拨打电话mmap?

如果可以的话为什么calloc不做吗？

有几种机制可以从操作系统获取预清零内存：

mmap(2)'s MAP_ANONYMOUSflag 强制内容初始化为零。

POSIX 共享内存段也可以清零

• shm_open(3)为您提供文件描述符
• ftruncate(2)将“文件”调整为您想要的大小
• mmap(2)将“文件”放入您的地址空间

内存已预先清零：

   This volume of IEEE Std 1003.1-2001 specifies that memory
   objects have initial contents of zero when created. This is
   consistent with current behavior for both files and newly
   allocated memory. For those implementations that use physical
   memory, it would be possible that such implementations could
   simply use available memory and give it to the process
   uninitialized. This, however, is not consistent with standard
   behavior for the uninitialized data area, the stack, and of
   course, files. Finally, it is highly desirable to set the
   allocated memory to zero for security reasons. Thus,
   initializing memory objects to zero is required.

看来该内存已归零use: mm/shmem.c功能shmem_zero_setup():

/**
 * shmem_zero_setup - setup a shared anonymous mapping
 * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
 */     
int shmem_zero_setup(struct vm_area_struct *vma)
{   
    struct file *file;
    loff_t size = vma->vm_end - vma->vm_start;

    file = shmem_file_setup("dev/zero", size, vma->vm_flags);
    if (IS_ERR(file))
        return PTR_ERR(file);

    if (vma->vm_file)
        fput(vma->vm_file);
    vma->vm_file = file;
    vma->vm_ops = &shmem_vm_ops;
    return 0;
}