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2851. std::filesystem enum classes are now underspecified

Section: 28.11.9.2 [fs.enum.file_type], 28.11.9.3 [fs.enum.copy.opts], 28.11.9.6 [fs.enum.dir.opts] Status: WP Submitter: Tim Song Opened: 2016-12-18 Last modified: 2018-03-24

Priority: 2

View all other issues in [fs.enum.file_type].

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Discussion:

LWG 2678 stripped the numerical values of the enumerators from three enum classes in 28.11.9 [fs.enum]; in doing so it also removed the implicit specification 1) of the bitmask elements for the two bitmask types (copy_options and directory_options) and 2) that the file_type constants are distinct.

[2017-01-27 Telecon]

Priority 2; Jonathan to work with Tim to tweak wording.

[2018-01-16, Jonathan comments]

I no longer remember what I didn't like about Tim's P/R so I think we should accept the original P/R.

[2018-1-26 issues processing telecon]

Status to 'Tentatively Ready'

[2018-3-17 Adopted in Jacksonville]

Proposed resolution:

This wording is relative to N4713.

  1. Edit 28.11.9.2 [fs.enum.file_type]/1 as indicated:

    This enum class specifies constants used to identify file types, with the meanings listed in Table 123. The values of the constants are distinct.

  2. Edit 28.11.9.3 [fs.enum.copy.opts]/1 as indicated:

    The enum class type copy_options is a bitmask type (15.4.2.1.4 [bitmask.types]) that specifies bitmask constants used to control the semantics of copy operations. The constants are specified in option groups with the meanings listed in Table 124. The constant none represents the empty bitmask, and Constant none is shown in each option group for purposes of exposition; implementations shall provide only a single definition. Every other constant in the table represents a distinct bitmask element. Calling a library function with more than a single constant for an option group results in undefined behavior.

  3. Edit 28.11.9.6 [fs.enum.dir.opts]/1 as indicated:

    The enum class type directory_options is a bitmask type (15.4.2.1.4 [bitmask.types]) that specifies bitmask constants used to identify directory traversal options, with the meanings listed in Table 127. The constant none represents the empty bitmask; every other constant in the table represents a distinct bitmask element.