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### 665. `do_unshift` return value

Section: 30.4.2.5.3 [locale.codecvt.virtuals] Status: CD1 Submitter: Thomas Plum Opened: 2007-04-16 Last modified: 2016-01-28

Priority: Not Prioritized

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Discussion:

30.4.2.5.3 [locale.codecvt.virtuals], para 8 says:

> `codecvt<char,char,mbstate_t>`, returns `noconv`.

The following objection has been raised:

> Despite what the C++ Standard says, `unshift` can't always return `noconv` for the default facets, since they can be nontrivial. At least one implementation does whatever the C functions do.

[Plum ref _222152Y62]

Proposed resolution:

Change 30.4.2.5.3 [locale.codecvt.virtuals], p8:

> Returns: An enumeration value, as summarized in Table 76:

> ...

> `codecvt<char,char,mbstate_t>`, returns `noconv`.