的malloc分配内存比RAM更 [英] Malloc allocates memory more than RAM

问题描述

我只是执行的，在一个12 MB的计算机mallocs 13 MB的程序（QEMU模拟！）。不仅如此，我甚至通过记忆浏览，并在其中填满垃圾......

I just executed a program that mallocs 13 MB in a 12 MB machine (QEMU Emulated!) . Not just that, i even browsed through the memory and filled junk in it...

void 
large_mem(void) 
{
  #define LONGMEM  13631488
  long long *ptr = (long long *)malloc(LONGMEM);
  long long i;
  if(!ptr) {
     printf("%s(): array allocation of size %lld failed.\n",__func__,LONGMEM);
     ASSERT(0);
  }
  for(i = 0 ; i < LONGMEM ; i++ ) { 
    *(ptr+i)=i;
  }
  free(ptr);
}

这怎么可能？我期待分段错误。

How is it possible ? I was expecting a segmentation fault.

推荐答案

这就是所谓的虚拟内存这是分配给你的程序。这不是的真正的内存，您拨打的RAM。

It's called virtual memory which is allocated for your program. It's not real memory which you call RAM.

有对虚拟内存最大限制为好，但它比RAM高。它是由你的操作系统实现（定义）。

There is a max limit for virtual memory as well, but it's higher than RAM. It's implemented (and defined) by your operating system.

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