[2026-06 LWG Motion 6] P3395R6 (Fix encoding issues and add a formatter for std::error_code)#9129
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[2026-06 LWG Motion 6] P3395R6 (Fix encoding issues and add a formatter for std::error_code)#9129notdanhan wants to merge 1 commit into
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eisenwave
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Jun 18, 2026
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Needs a fair amount of work, mainly converting to \grammarterm.
| Equivalent to: \tcode{return os << ec.category().name() << ':' << ec.value();} | ||
| \end{itemdescr} | ||
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| \rSec3[system.error.fmt]{Formatting} |
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It's not your fault, but this subclause stable name makes no sense. Everything else is called [syserr.*] except for [system.error.syn].
We probably want something like [syserr.fmt] or whatever the convention is for "formatting support" stable names.
| \rSec3[system.error.fmt]{Formatting} | ||
| \pnum | ||
| \begin{codeblock} | ||
| template<class charT> struct formatter<error_code, charT> { |
| }; | ||
| \end{codeblock} | ||
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| \pnum |
| \pnum | ||
| \effects | ||
| Modifies the state of the \tcode{formatter} to be as if the | ||
| \defnx{error-code-format-spec}{error-code-format-spec!syserr err fmt} passed by the |
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| \defnx{error-code-format-spec}{error-code-format-spec!syserr err fmt} passed by the | |
| \grammarterm{error-code-format-spec} passed by the |
The paper italics are grammarterm italics, not defining.
| last call to \tcode{parse} contained the \tcode{?} option. | ||
| \end{itemdescr} | ||
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| \pnum |
| \opt{fill-and-align} \opt{width} \opt{\tcode{?}} \opt{\tcode{s}} | ||
| \end{ncbnf} | ||
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| where the productions and \defnx{width}{width!format string} are described in\iref{format.string} |
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| where the productions and \defnx{width}{width!format string} are described in\iref{format.string} | |
| where the productions \grammarterm{fill-and-align} and \grammarterm{width} are described in\iref{format.string}. |
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| \item If \tcode{charT} is \tcode{char} and the ordinary literal encoding is UTF-8, let | ||
| \tcode{msg} be \tcode{ec.message()} transcoded to UTF-8 with maximal subparts of ill-formed | ||
| subsequences substituted with \unicode{fffd}{replacement character} per the Unicode Standard, Chapter | ||
| 3.9 \unicode{fffd} Substitution in Conversion. | ||
| \item Otherwise, let \tcode{msg} be \tcode{ec.message()} transcoded to an implementation-defined encoding. |
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Needs some reflowing:
Suggested change
| \item If \tcode{charT} is \tcode{char} and the ordinary literal encoding is UTF-8, let | |
| \tcode{msg} be \tcode{ec.message()} transcoded to UTF-8 with maximal subparts of ill-formed | |
| subsequences substituted with \unicode{fffd}{replacement character} per the Unicode Standard, Chapter | |
| 3.9 \unicode{fffd} Substitution in Conversion. | |
| \item Otherwise, let \tcode{msg} be \tcode{ec.message()} transcoded to an implementation-defined encoding. | |
| \item | |
| If \tcode{charT} is \tcode{char} and the ordinary literal encoding is UTF-8, | |
| let \tcode{msg} be \tcode{ec.message()} transcoded to UTF-8 | |
| with maximal subparts of ill-formed subsequences substituted with \unicode{fffd}{replacement character} | |
| per the Unicode Standard, Chapter 3.9 \unicode{fffd} Substitution in Conversion. | |
| \item | |
| Otherwise, let \tcode{msg} be \tcode{ec.message()} | |
| transcoded to an implementation-defined encoding. |
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Fixes: #9093
Also Fixes cplusplus/papers#2187