2507. codecvt_mode should be a bitmask type

Section: D.17 [depr.locale.stdcvt] Status: New Submitter: Jonathan Wakely Opened: 2015-06-08 Last modified: 2017-05-13

Priority: 3

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Discussion:

The enumeration type codecvt_mode is effectively a bitmask type (20.4.2.1.4 [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: