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2489. mem_fn() should be noexcept

Section: 22.10.16 [func.memfn] Status: C++17 Submitter: Stephan T. Lavavej Opened: 2015-03-27 Last modified: 2017-07-30

Priority: 0

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Discussion:

mem_fn() is wide contract and doesn't do anything that could throw exceptions, so it should be marked noexcept.

Note that mem_fn() is perfectly happy to wrap a null PMF/PMD, it just can't be invoked later. This is exactly like std::function, which can be constructed from null PMFs/PMDs. Therefore, mem_fn() will remain wide contract forever.

[2015-05, Lenexa]

Move to Immediate.

Proposed resolution:

This wording is relative to N4296.

1. Change 22.10 [function.objects] p2 "Header <functional> synopsis" as depicted:

   […]
   // 20.9.11, member function adaptors:
   template<class R, class T> unspecified mem_fn(R T::*) noexcept;
   […]
   

2. Change 22.10.16 [func.memfn] as depicted:

   template<class R, class T> unspecified mem_fn(R T::* pm) noexcept;
   

   […]

   -4- Throws: Nothing.