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### 1371. Standard exceptions require stronger no-throw guarantees

Section: 19 [diagnostics] Status: NAD Submitter: BSI Opened: 2010-08-25 Last modified: 2016-01-28

Priority: Not Prioritized

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Discussion:

Addresses GB-75

None of the exception types defined in clause 19 are allowed to throw an exception on copy or move operations, but there is no clear specification that the operations have an exception specification to prove it. Note that the implicitly declared constructors, taking the exception specification from their base class (ultimately `std::exception`) will implicitly generate a `noexcept` exception specification if all of their data members similarly declare `noexcept` operations. As the representation is unspecified, we cannot assume nonthrowing operations unless we explicitly state this as a constraint on the implementation.

[ Resolution proposed by ballot comment: ]

Add a global guarantee that all exception types defined in clause 19 that rely on implicitly declared operations have a non-throwing exception specification on those operations.

[ 2010 Batavia: ]

This is addressed by the current words in 18.8.1 [exception], p2

> Each standard library class `T` that derives from class `exception` shall have a publicly accessible copy constructor and a publicly accessible copy assignment operator that do not exit with an exception.

Proposed resolution: