问题描述
::operator new(size_t)是在内部调用malloc()，还是直接使用系统调用/特定于OS的库调用? C ++标准怎么说?
Does ::operator new(size_t) call malloc() internally, or does it use system calls / OS-specific library calls directly? What does the C++ standard say?
在此答案中表示:
这表明可以不需要new()来调用malloc().
And that suggests that new() cannot be required to call malloc().
注意:这里有一个问题关于operator new除分配以外的其他操作.
Note: There's an SO question about everything operator new does other than allocation.
推荐答案
operator new的实现方式的详细信息是标准库的特定实现的属性-甚至不是编译器或操作系统.我熟悉一个(gnu)，并且知道另外3个-CLang，Apache和MSFT.他们所有人都在operator new中使用malloc()，因为它使图书馆开发人员的工作变得如此轻松.
The details of how operator new is implemented are property of a particular implementation of standard library - not even a compiler or operation system. I am familiar with one (gnu) and aware of 3 others - CLang, Apache and MSFT. All of them are using malloc() within operator new, because it just makes a life of library developer so much easier.
如果不使用malloc()，则表示开发人员将不得不在内存分配方面重新实现很多功能，并在代码中大量使用依赖于OS的逻辑来实际请求内存.当malloc()已经存在时，没有人愿意这样做.但是他们绝没有义务使用它.
If malloc() were not used, said developer would have to reimplement a lot in terms of memory allocation, and sprinkle the code heavily with OS-dependent logic to actually request memory. No one wants to do this when malloc() is already there. But by no means they are obliged to use it.
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