什么是由malloc的取得了Windows和Linux的本机OS /系统调用（）？ [英] What are the Windows and Linux native OS/system calls made from malloc()?

问题描述

我最近看到以下职位：

一个内存分配器不低于malloc的较低水平。 （默认
  通常分配直接或间接）调用malloc

A memory allocator isn't lower level than malloc. (The default allocator typically calls malloc directly or indirectly)

这是分配器只允许你指定不同的分配
  策略。例如，你可以使用它调用malloc分配器
  一旦检索一个大的内存池，然后为后续
  分配请求，它只是返回此池的一小块。

An allocator just allows you to specify different allocation strategies. For example, you might use an allocator which calls malloc once to retrieve a large pool of memory, and then for subsequent allocation requests, it just returns a small chunk of this pool.

或者你可以使用它作为一个钩子，让你执行一些附加
  每次内存分配或释放任务。

Or you may use it as a hook to allow you to perform some additional task every time memory is allocated or freed.

关于你的第二个问题，是的malloc你可以去无最低
  失去了便携性。 的malloc通常使用一些实施
  OS专用内存分配函数，所以这将是较低水平
  仍然。但是，这无关你的主要问题，因为C ++
  分配器是一个更高层次的抽象。

As to your second question, malloc is the lowest you can go without losing portability. malloc is typically implemented using some OS-specific memory allocation function, so that would be lower level still. But that's unrelated to your main question, since C++ allocators are a higher-level abstraction.

来自： C ++：内存分配

我的问题是 - 如何在以下操作系统实现的malloc？

My question is- how is malloc implemented in the following Operating systems?

• 对于Windows


• 用于Linux

什么是被称为操作系统特定的函数/的malloc（）的实现？

what are the OS-specific functions which are called/implementations of malloc()?

推荐答案

在Windows中，在最新版本的MSVC，的malloc（和C ++ 新，因为它是使用实施对于实际的内存分配部分相同的基本面新）调用<一个href=\"http://msdn.microsoft.com/en-us/library/aa366597%28v=vs.85%29.aspx\"><$c$c>HeapAlloc().在其他的版本，比如G ++ MinGW的，C运行时是较旧的版本，这并不完全是直接打电话到 HeapAlloc ，但在它的基础，它仍然去 HeapAlloc - 找不同的东西，我们需要回去到Windows pre-95，它确实有一个的GlobalAlloc 和 LocalAlloc 的功能集 - 但我不认为人们使用16位编译器这些日子 - 至少不适用于Windows编程

In Windows, in recent versions of MSVC, malloc (and C++ new, as it is implemented using the same fundamentals for the actual memory allocation part of new) calls HeapAlloc(). In other versions, such as g++ mingw, the C runtime is an older version, which doesn't call quite as directly to HeapAlloc, but at the base of it, it still goes to HeapAlloc - to find something different, we need to go back to Windows pre-95, which did have a GlobalAlloc and LocalAlloc set of functions - but I don't think people use 16-bit compilers these days - at least not for Windows programming.

在Linux上，如果您使用的是的glibc ，这取决于分配的大小是否它调用的 SBRK 或的 MMAP - MMAP （用 MAP_ANONYMOUS 中的标志），用于分配的较大（超过阈值，我相信这是在2MB典型的实现）

In Linux, if you are using glibc, it depends on the size of the allocation whether it calls sbrk or mmap - mmap (with MAP_ANONYMOUS in the flags) is used for larger allocations (over a threshold, which I believe is 2MB in the typical implementation)

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