由new分配的free()内存安全吗? [英] Is it safe to free() memory allocated by new?

问题描述

我正在使用C ++库，该库的函数之一返回指向双精度数组的(新分配的)指针.该API指出，调用者有责任重新分配内存.

I'm working on a C++ library, one of whose functions returns a (freshly allocated) pointer to an array of doubles. The API states that it is the responsibility of the caller to deallocate the memory.

但是，该C ++库以前是用C实现的，所涉及的函数使用 malloc()分配内存.它还假定调用方将使用 free()释放该内存.

However, that C++ library used to be implemented in C and the function in question allocates the memory with malloc(). It also assumes that the caller will deallocate that memory with free().

我可以安全地将对 malloc()的调用替换为对 new 的调用吗?如果这样做，现有的客户端代码(使用 free()的代码是否会中断?)到目前为止，我所能找到的只是 free()的官方文档，其中指出

Can I safely replace the call to malloc() with a call to new? Will the existing client code (that uses free() break if I do so? All I could find so far was the official documentation of free(), which states that

如果ptr不指向使用[malloc，calloc或realloc]分配的内存块，则会导致未定义的行为.

If ptr does not point to a block of memory allocated with [malloc, calloc or realloc], it causes undefined behavior.

但是我相信这是在C ++附带其自己的分配运算符之前编写的.

But I believe this was written before C++ came along with its own allocation operators.

推荐答案

不允许将 malloc 和 free 与 new 混合和匹配>和 delete 草案，C ++标准为此参考了C99标准，如果我们转到

You are not allowed to mix and match malloc and free with new and delete the draft C++ standard refers back to the C99 standard for this and if we go to the draft C++ standard section 20.6.13 C library it says (emphasis mine going forward):

内容与标准C库标头stdlib.h相同，但有以下更改:

The contents are the same as the Standard C library header stdlib.h, with the following changes:

和:

函数calloc()，malloc()和realloc()不会尝试通过调用:: operator来分配存储new()(18.6).

The functions calloc(), malloc(), and realloc() do not attempt to allocate storage by calling ::operator new() (18.6).

和:

free()函数不会通过调用:: operator delete()来尝试取消分配存储.另请参阅:ISO C条款7.11.2.

The function free() does not attempt to deallocate storage by calling ::operator delete(). See also: ISO C Clause 7.11.2.

并包括其他更改，我们无法对通过 new 分配的内容使用 free 的任何状态.因此，C99标准草案中的 7.20.3.2 免费功能部分仍然是正确的参考，它说:

and includes other changes, none of which state that we can use free on contents allocated with new. So section 7.20.3.2 The free function from the draft C99 standard is still the proper reference and it says:

否则，如果参数与早期由calloc，malloc或realloc函数返回的指针不匹配，或者如果通过调用free或realloc释放了空间，则行为未定义>.

这篇关于由new分配的free()内存安全吗?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！