Issue 819: rethrow_if

This page is a snapshot from the LWG issues list, see the Library Active Issues List for more information and the meaning of C++11 status.

819. rethrow_if_nested

Section: 17.9.8 [except.nested] Status: C++11 Submitter: Alisdair Meredith Opened: 2008-03-25 Last modified: 2016-01-28

Priority: Not Prioritized

View all other issues in [except.nested].

View all issues with C++11 status.

Discussion:

Looking at the wording I submitted for rethrow_if_nested, I don't think I got it quite right.

The current wording says:

template <class E> void rethrow_if_nested(const E& e);
Effects: Calls e.rethrow_nested() only if e is publicly derived from nested_exception.

This is trying to be a bit subtle, by requiring e (not E) to be publicly derived from nested_exception the idea is that a dynamic_cast would be required to be sure. Unfortunately, if e is dynamically but not statically derived from nested_exception, e.rethrow_nested() is ill-formed.

[ San Francisco: ]

Alisdair was volunteered to provide wording.

[ 2009-10 Santa Cruz: ]

Leave as Open. Alisdair to provide wording.

[ 2009-11-09 Alisdair provided wording. ]

[ 2010-03-10 Dietmar updated wording. ]

[ 2010 Pittsburgh: ]

Moved to Ready for Pittsburgh.

Proposed resolution:

Change 17.9.8 [except.nested], p8:

template <class E> void rethrow_if_nested(const E& e);
-8- Effects: ~~Calls e.rethrow_nested() o~~Only if the dynamic type of e is publicly and unambiguously derived from nested_exception this calls dynamic_cast<const nested_exception&>(e).rethrow_nested().