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2373. Make new entities and names in namespace std conforming extensions

Section: 15.5.5 [conforming] Status: NAD Submitter: Chandler Carruth Opened: 2014-03-22 Last modified: 2016-12-23

Priority: 3

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Discussion:

Technically, right now, it is not a conforming extension to add a new function to namespace std. Doing so could cause unqualified lookup on the name of that function in the presence of a using directive to find a different function. This seems an unreasonable restriction on library vendors providing conforming extensions, as such a using directive seems inherently risky in unqualified name lookup.

15.5.5.5 [member.functions] implies that adding overloads to a method is a conforming extension, and within some limits the same is true for global functions due to 15.5.5.4 [global.functions].

It would likely be useful to specify that other new entities are valid conforming extensions, or preclude them where they pose serious compatibility problems.

[Lenexa 2015-05-06: Move to NAD]

JY: It's a design question, move to LEWG?

AM: NAD: extensions led to us being unable to use the names hash_map, leading to unordered_map etc. Will result in collisions between members.

MC: Agrees, implementations that extend std:: must use __ugly_names for this reason.

JY: I would not oppose NAD.

Move to NAD, consensus.

Proposed resolution: