c++ - 除了重新抛出 std::exception_ptr 之外，我还能做什么

Question

我有一个 std::exception_ptr 类型的对象，我想在它上面调用 what()，但似乎没有办法做到这一点(如本答案中所述:How do I make a call to what() on std::exception_ptr)。

在互联网上搜索后，似乎除了重新抛出它并在 std::exception& 中捕获它之外我无法对它做任何事情。

这对我来说有点奇怪，但我想检查一下:std::exception_ptr 可以做什么，然后重新抛出它以获得期望的细节？

C++14或其他版本的C++有什么变化

Answer 1

不幸的是，没有。该标准仅保证 std::exception_ptr 的以下内容:

18.8.5 Exception propagation

1 The type exception_ptr can be used to refer to an exception object.

2 exception_ptr shall satisfy the requirements of NullablePointer (17.6.3.3).

3 Two non-null values of type exception_ptr are equivalent and compare equal if and only if they refer to the same exception.

4 The default constructor of exception_ptr produces the null value of the type.

5 exception_ptr shall not be implicitly convertible to any arithmetic, enumeration, or pointer type.

7 For purposes of determining the presence of a data race, operations on exception_ptr objects shall access and modify only the exception_ptr objects themselves and not the exceptions they refer to.

此外，注意到 here ,

Performing any other operation on the object (such as dereferencing it), if at all supported by the library implementation, causes undefined behavior.