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3648. format should not print bool with 'c'

Section: [format.string.std] Status: C++23 Submitter: Zhihao Yuan Opened: 2021-11-30 Last modified: 2023-11-22

Priority: Not Prioritized

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P1652R1 prints integral inputs as characters with 'c' and preserves the wording to treat bool as a one-byte unsigned integer; this accidentally asks the implementation to cast bool into a 1-bit character if a user asks for the 'c' presentation type.

Recent wording improvements made this implied behavior obvious.

[2021-12-04; Daniel comments]

This issue relates to LWG 3644.

[2022-01-30; Reflector poll]

Set status to Tentatively Ready after five votes in favour during reflector poll.

[2022-02-10 Approved at February 2022 virtual plenary. Status changed: Tentatively Ready → WP.]

Proposed resolution:

This wording is relative to N4901.

  1. Modify [format.string.std], Table 67 [tab:format.type.bool], as indicated:

    Table 67 — Meaning of type options for bool [tab:format.type.bool]
    Type Meaning
    none, s Copies textual representation, either true or false, to the output.
    b, B, c, d, o, x, X As specified in Table 65 [] for the value static_cast<unsigned char>(value).