Piotr Dulikowski e87cf08591 exception_container: switch impl to std::shared_ptr and make copyable ...

The exception_container is supposed to be a cheaper, but possibly harder
to use alternative to std::exception_ptr. Before this commit, the
exception was kept behind foreign_ptr<std::unique_ptr<>> so that moving
the container is very cheap. However, the original std::exception_ptr
supports copying in a thread-safe manner, and it turns out that some of
the read coordinator logic intentionally copies the pointer in order to
be able to fail two different promises with the same exception.

The pointer type is changed to std::shared_ptr. Although it uses atomics
for reference counting, this is also probably what std::exception_ptr
does, so the performance should not be worse. The exception stored
inside the container is immutable, so this allows for a non-throwing
implementation of copying.

To encourage moves instead of copying, the copy constructor is deleted
and instead the `clone()` method should be used if it is really
necessary.

2022-02-22 16:08:52 +01:00

5.2 KiB

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