Merge 2021-10 LWG Motion 2

P2372R3 Fixing locale handling in chrono formatters

Author: tkoeppe

source/support.tex

@@ -609,7 +609,7 @@
 #define @\defnlibxname{cpp_lib_exchange_function}@                 201304L // also in \libheader{utility}
 #define @\defnlibxname{cpp_lib_execution}@                         201902L // also in \libheader{execution}
 #define @\defnlibxname{cpp_lib_filesystem}@                        201703L // also in \libheader{filesystem}
-#define @\defnlibxname{cpp_lib_format}@                            202106L // also in \libheader{format}
+#define @\defnlibxname{cpp_lib_format}@                            202110L // also in \libheader{format}
 #define @\defnlibxname{cpp_lib_gcd_lcm}@                           201606L // also in \libheader{numeric}
 #define @\defnlibxname{cpp_lib_generic_associative_lookup}@        201304L // also in \libheader{map}, \libheader{set}
 #define @\defnlibxname{cpp_lib_generic_unordered_lookup}@          201811L

source/time.tex

@@ -2717,9 +2717,7 @@
 \effects
 Equivalent to:
 \begin{codeblock}
-auto const dp = floor<days>(tp);
-return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{} {}"),
-                    year_month_day{dp}, hh_mm_ss{tp-dp});
+return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@("{:L%F %T}"), tp);
 \end{codeblock}
 
 \pnum
@@ -2915,7 +2913,7 @@
 \effects
 Equivalent to:
 \begin{codeblock}
-return os << format(@\placeholder{STATICALLY-WIDEN}@<charT>("{:%F %T}"), t);
+return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{:L%F %T}"), t);
 \end{codeblock}
 
 \pnum
@@ -3121,7 +3119,7 @@
 \effects
 Equivalent to:
 \begin{codeblock}
-return os << format(@\placeholder{STATICALLY-WIDEN}@<charT>("{:%F %T}"), t);
+return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{:L%F %T}"), t);
 \end{codeblock}
 
 \pnum
@@ -3284,7 +3282,7 @@
 \effects
 Equivalent to:
 \begin{codeblock}
-return os << format(@\placeholder{STATICALLY-WIDEN}@<charT>("{:%F %T}"), t);
+return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{:L%F %T}"), t);
 \end{codeblock}
 
 \pnum
@@ -3407,7 +3405,7 @@
 \effects
 Equivalent to:
 \begin{codeblock}
-return os << format(@\placeholder{STATICALLY-WIDEN}@<charT>("{:%F %T}"), t);
+return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{:L%F %T}"), t);
 \end{codeblock}
 \end{itemdescr}
 
@@ -4483,7 +4481,7 @@
 Equivalent to:
 \begin{codeblock}
 return os << (m.ok() ?
-  format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{:%b}"), m) :
+  format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{:L%b}"), m) :
   format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{} is not a valid month"),
          static_cast<unsigned>(m)));
 \end{codeblock}
@@ -5210,7 +5208,7 @@
 Equivalent to:
 \begin{codeblock}
 return os << (wd.ok() ?
-  format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{:%a}"), wd) :
+  format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{:L%a}"), wd) :
   format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{} is not a valid weekday"),
          static_cast<unsigned>(wd.wd_)));
 \end{codeblock}
@@ -5364,8 +5362,8 @@
 \begin{codeblock}
 auto i = wdi.index();
 return os << (i >= 1 && i <= 5 ?
-  format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{}[{}]"), wdi.weekday(), i) :
-  format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{}[{} is not a valid index]"),
+  format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{:L}[{}]"), wdi.weekday(), i) :
+  format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{:L}[{} is not a valid index]"),
          wdi.weekday(), i));
 \end{codeblock}
 \end{itemdescr}
@@ -5467,7 +5465,7 @@
 \effects
 Equivalent to:
 \begin{codeblock}
-return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{}[last]"), wdl.weekday());
+return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{:L}[last]"), wdl.weekday());
 \end{codeblock}
 \end{itemdescr}
 
@@ -5594,7 +5592,7 @@
 \effects
 Equivalent to:
 \begin{codeblock}
-return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{}/{}"),
+return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{:L}/{}"),
                     md.month(), md.day());
 \end{codeblock}
 \end{itemdescr}
@@ -5731,7 +5729,7 @@
 \effects
 Equivalent to:
 \begin{codeblock}
-return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{}/last"), mdl.month());
+return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{:L}/last"), mdl.month());
 \end{codeblock}
 \end{itemdescr}
 
@@ -5844,7 +5842,7 @@
 \effects
 Equivalent to:
 \begin{codeblock}
-return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{}/{}"),
+return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{:L}/{:L}"),
                     mwd.month(), mwd.weekday_indexed());
 \end{codeblock}
 \end{itemdescr}
@@ -5960,7 +5958,7 @@
 \effects
 Equivalent to:
 \begin{codeblock}
-return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{}/{}"),
+return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{:L}/{:L}"),
                     mwdl.month(), mwdl.weekday_last());
 \end{codeblock}
 \end{itemdescr}
@@ -6274,7 +6272,7 @@
 \effects
 Equivalent to:
 \begin{codeblock}
-return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{}/{}"),
+return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{}/{:L}"),
                     ym.year(), ym.month());
 \end{codeblock}
 \end{itemdescr}
@@ -7133,7 +7131,7 @@
 \effects
 Equivalent to:
 \begin{codeblock}
-return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{}/{}"),
+return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{}/{:L}"),
                     ymdl.year(), ymdl.month_day_last());
 \end{codeblock}
 \end{itemdescr}
@@ -7529,7 +7527,7 @@
 \effects
 Equivalent to:
 \begin{codeblock}
-return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{}/{}/{}"),
+return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{}/{:L}/{:L}"),
                     ymwd.year(), ymwd.month(), ymwd.weekday_indexed());
 \end{codeblock}
 \end{itemdescr}
@@ -7877,7 +7875,7 @@
 \effects
 Equivalent to:
 \begin{codeblock}
-return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{}/{}/{}"),
+return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{}/{:L}/{:L}"),
                     ymwdl.year(), ymwdl.month(), ymwdl.weekday_last());
 \end{codeblock}
 \end{itemdescr}
@@ -8623,7 +8621,7 @@
 \effects
 Equivalent to:
 \begin{codeblock}
-return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{:%T}"), hms);
+return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{:L%T}"), hms);
 \end{codeblock}
 
 \pnum
@@ -10100,14 +10098,10 @@
 \begin{itemdescr}
 \pnum
 \effects
-Streams
-the value returned from \tcode{t.get_local_time()}
-to \tcode{os}
-using the format \tcode{"\%F \%T \%Z"}.
-
-\pnum
-\returns
-\tcode{os}.
+Equivalent to:
+\begin{codeblock}
+return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@("{:L%F %T %Z}"), t);
+\end{codeblock}
 \end{itemdescr}
 
 \rSec2[time.zone.leap]{Class \tcode{leap_second}}
@@ -10446,7 +10440,7 @@
 
 \begin{ncbnf}
 \fmtnontermdef{chrono-format-spec}\br
-    \opt{fill-and-align} \opt{width} \opt{precision} \opt{chrono-specs}
+    \opt{fill-and-align} \opt{width} \opt{precision} \opt{\terminal{L}} \opt{chrono-specs}
 \end{ncbnf}
 
 \begin{ncbnf}
@@ -10495,15 +10489,26 @@
 represented by \fmtgrammarterm{literal-char}
 are copied unchanged to the output.
 
+\pnum
+A \defnadj{formatting}{locale} is an instance of \tcode{locale}
+used by a formatting function, that is determined as follows:
+\begin{itemize}
+\item
+the \tcode{"C"} locale if the \tcode{L} option
+is not present in \fmtgrammarterm{chrono-format-spec}, otherwise
+\item
+the locale passed to the formatting function if any, otherwise
+\item
+the global locale.
+\end{itemize}
+
 \pnum
 Each conversion specifier \fmtgrammarterm{conversion-spec}
 is replaced by appropriate characters
 as described in \tref{time.format.spec};
 the formats specified in ISO 8601:2004 shall be used where so described.
 Some of the conversion specifiers
-depend on the locale that is passed to the formatting function
-if the latter takes one,
-or the global locale otherwise.
+depend on the formatting locale.
 If the formatted object does not contain the information
 the conversion specifier refers to,
 an exception of type \tcode{format_error} is thrown.
@@ -10778,6 +10783,7 @@
 If the \fmtgrammarterm{chrono-specs} is omitted,
 the chrono object is formatted
 as if by streaming it to \tcode{std::ostringstream os}
+with the formatting locale imbued
 and copying \tcode{os.str()} through the output iterator of the context
 with additional padding and adjustments as specified by the format specifiers.
 \begin{example}