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### 2008. Conflicting Error Conditions for `packaged_task::operator()`

Section: 32.9.10.2 [futures.task.members] Status: C++11 Submitter: Pete Becker Opened: 2010-06-21 Last modified: 2016-01-28

Priority: Not Prioritized

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Discussion:

The Throws clause for `packaged_task::operator()` says that it throws "a `future_error` exception object if there is no associated asynchronous state or the stored task has already been invoked." However, the Error Conditions clause does not define an error condition when the stored task has already been invoked, only when the associated state is already ready (i.e. the invocation has completed).

[2011-02-17 Anthony provides an alternative resolution]

Previous proposed resolution:

Change the first bullet item in 32.9.10.2 [futures.task.members] /22:

>     void operator()(ArgTypes... args);

> > 20 ...

> > 21 ...

> > 22 Error conditions:

> > - `promise_already_satisfied` if the associated asynchronous state is already ready `operator()` has already been called.
> > - `no_state` if `*this` has no associated asynchronous state.

[Adopted at Madrid, 2011-03]

Proposed resolution:

1. Change the first bullet item in 32.9.10.2 [futures.task.members] p. 17:

   >     void operator()(ArgTypes... args);

   > > 15 ...

   > > 16 ...

   > > 17 Error conditions:

   > > - `promise_already_satisfied` if the associated asynchronous state is already ready stored task has already been invoked.
   > > - `no_state` if `*this` has no associated asynchronous state.

2. Change the first bullet item in 32.9.10.2 [futures.task.members] p. 21:

   >     void make_ready_at_thread_exit(ArgTypes... args);

   > > 19 ...

   > > 20 ...

   > > 21 Error conditions:

   > > - `promise_already_satisfied` if the associated asynchronous state already has a stored value or exception stored task has already been invoked.
   > > - `no_state` if `*this` has no associated asynchronous state.