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### 2507. `codecvt_mode` should be a bitmask type

Section: D.22 [depr.locale.stdcvt] Status: New Submitter: Jonathan Wakely Opened: 2015-06-08 Last modified: 2017-04-22

Priority: 3

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Discussion:

The enumeration type `codecvt_mode` is effectively a bitmask type (16.3.3.3.4 [bitmask.types]) with three elements, but isn't defined as such.

This harms usability because bitmask types are required to work well with bitwise operators, but `codecvt_mode` doesn't have overloaded operators, making it very inconvenient to combine values:

>     std::codecvt_utf16<char32_t, 0x10FFFF,
>       static_cast<std::codecvt_mode>(std::little_endian|std::generate_header)>
>     cvt;

The `static_cast` harms readability and should not be necessary.

I suggest that either `codecvt_mode` is specified to be a bitmask type, or as a minimal fix we provide an overloaded `operator|` that returns the right type.

Proposed resolution: