使用分配器

发布于 2024-10-27 15:41:56 字数 757 浏览 1 评论 0原文

这些版本的new和delete是否异常安全？有什么可能的陷阱吗？

假设 customized_allocator_type 与 STL 兼容。还假设分配器的构造函数没有任何副作用，并且所有实例都是等效的。

预先感谢您的意见！

template <typename T>
inline T * customized_new(const T& t)
{
    customized_allocator_type<T> alloc;
    T * ptr = alloc.allocate(1);

    if (ptr==0)
        throw std::bad_alloc();

    try {
        alloc.construct(ptr, t);
    } catch (...) {
        alloc.deallocate(ptr, 1);
        throw;
    }

    return ptr;
}


template <typename T>
inline void customized_delete(T * ptr)
{
    if (ptr==0)
        return;

    customized_allocator_type<T> alloc;
    alloc.destroy(ptr);
    alloc.deallocate(ptr, 1);
};

原文

Are these versions of new and delete are exception safe? Any possible pitfalls?

Assume that customized_allocator_type is STL compatible. Also assume that the allocator's constructor doesn't have any side effect and all instances are equivalent.

Thanks in advance for your input!

template <typename T>
inline T * customized_new(const T& t)
{
    customized_allocator_type<T> alloc;
    T * ptr = alloc.allocate(1);

    if (ptr==0)
        throw std::bad_alloc();

    try {
        alloc.construct(ptr, t);
    } catch (...) {
        alloc.deallocate(ptr, 1);
        throw;
    }

    return ptr;
}


template <typename T>
inline void customized_delete(T * ptr)
{
    if (ptr==0)
        return;

    customized_allocator_type<T> alloc;
    alloc.destroy(ptr);
    alloc.deallocate(ptr, 1);
};

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极致的悲 2024-11-03 15:41:56

这（充其量）是多余的：

if (ptr==0)
    throw std::bad_alloc();

如果 customized_allocator_type 满足标准库分配器要求，那么如果无法获取存储，它必须引发异常。从 allocate 返回 null 是不正确的。

This is (at best) redundant:

if (ptr==0)
    throw std::bad_alloc();

If customized_allocator_type is meeting the standard library allocator requirements then it must raise an exception if storage could not be obtained. Returning null from allocate would not be correct.

回复收藏 0 原文

冬天旳寂寞 2024-11-03 15:41:56

如果customized_allocator_type的construct()函数的行为已知它不会在异常时释放内存，那么你的解决方案是好的。

注意：customized_delete() 检查空指针时存在拼写错误 - 应该是：

if (ptr == 0)
  return;

If the behavior of customized_allocator_type's construct() function is known that it doesn't deallocate the memory on exception, then your solution is good.

Note: there is a typo in customized_delete() check for null pointer - it should be: