https://gcc.gnu.org/g:de45abc4b2a0446f374254981b59a19e0c6eebae
commit r13-8458-gde45abc4b2a0446f374254981b59a19e0c6eebae
Author: Jonathan Wakely <jwak...@redhat.com>
Date: Tue Aug 15 16:35:22 2023 +0100
libstdc++: Simplify chrono::__units_suffix using std::format
For std::chrono formatting we can simplify __units_suffix by using
std::format_to to generate the "[n/m]s" suffix with the correct
character type and write directly to the output iterator, so it doesn't
need to be widened using ctype. We can't remove the use of ctype::widen
for formatting a time zone abbreviation as a wide string, because that
can contain arbitrary characters that can't be widened by
__to_wstring_numeric.
This also fixes a bug in the chrono formatter for %Z which created a
dangling wstring_view.
libstdc++-v3/ChangeLog:
* include/bits/chrono_io.h (__units_suffix_misc): Remove.
(__units_suffix): Return a known suffix as string view, do not
write unknown suffixes to a buffer.
(__fmt_units_suffix): New function that formats the suffix using
std::format_to.
(operator<<, __chrono_formatter::_M_q): Use __fmt_units_suffix.
(__chrono_formatter::_M_Z): Correct lifetime of wstring.
(cherry picked from commit c992acdc6774ef3d566fab5f324d254bed1b9d4b)
Diff:
---
libstdc++-v3/include/bits/chrono_io.h | 84 ++++++++++++-----------------------
1 file changed, 29 insertions(+), 55 deletions(-)
diff --git a/libstdc++-v3/include/bits/chrono_io.h
b/libstdc++-v3/include/bits/chrono_io.h
index 1c08130bf65..1838ad1a8c6 100644
--- a/libstdc++-v3/include/bits/chrono_io.h
+++ b/libstdc++-v3/include/bits/chrono_io.h
@@ -38,7 +38,7 @@
#include <iomanip> // setw, setfill
#include <format>
-#include <bits/charconv.h>
+#include <bits/streambuf_iterator.h>
namespace std _GLIBCXX_VISIBILITY(default)
{
@@ -69,34 +69,9 @@ namespace __detail
#define _GLIBCXX_WIDEN_(C, S) ::std::chrono::__detail::_Widen<C>(S, L##S)
#define _GLIBCXX_WIDEN(S) _GLIBCXX_WIDEN_(_CharT, S)
-
- // Write an arbitrary duration suffix into the buffer.
- template<typename _Period>
- constexpr const char*
- __units_suffix_misc(char* __buf, size_t /* TODO check length? */) noexcept
- {
- namespace __tc = std::__detail;
- char* __p = __buf;
- __p[0] = '[';
- unsigned __nlen = __tc::__to_chars_len((uintmax_t)_Period::num);
- __tc::__to_chars_10_impl(__p + 1, __nlen, (uintmax_t)_Period::num);
- __p += 1 + __nlen;
- if constexpr (_Period::den != 1)
- {
- __p[0] = '/';
- unsigned __dlen = __tc::__to_chars_len((uintmax_t)_Period::den);
- __tc::__to_chars_10_impl(__p + 1, __dlen, (uintmax_t)_Period::den);
- __p += 1 + __dlen;
- }
- __p[0] = ']';
- __p[1] = 's';
- __p[2] = '\0';
- return __buf;
- }
-
template<typename _Period, typename _CharT>
- constexpr auto
- __units_suffix(char* __buf, size_t __n) noexcept
+ constexpr basic_string_view<_CharT>
+ __units_suffix() noexcept
{
// The standard say these are all narrow strings, which would need to
// be widened at run-time when inserted into a wide stream. We use
@@ -134,7 +109,22 @@ namespace __detail
_GLIBCXX_UNITS_SUFFIX(ratio<3600>, "h")
_GLIBCXX_UNITS_SUFFIX(ratio<86400>, "d")
#undef _GLIBCXX_UNITS_SUFFIX
- return __detail::__units_suffix_misc<_Period>(__buf, __n);
+ return {};
+ }
+
+ template<typename _Period, typename _CharT, typename _Out>
+ inline _Out
+ __fmt_units_suffix(_Out __out) noexcept
+ {
+ if (auto __s = __detail::__units_suffix<_Period, _CharT>(); __s.size())
+ return __format::__write(std::move(__out), __s);
+ else if constexpr (_Period::den == 1)
+ return std::format_to(std::move(__out), _GLIBCXX_WIDEN("[{}]s"),
+ (uintmax_t)_Period::num);
+ else
+ return std::format_to(std::move(__out), _GLIBCXX_WIDEN("[{}/{}]s"),
+ (uintmax_t)_Period::num,
+ (uintmax_t)_Period::den);
}
} // namespace __detail
/// @endcond
@@ -149,14 +139,14 @@ namespace __detail
operator<<(std::basic_ostream<_CharT, _Traits>& __os,
const duration<_Rep, _Period>& __d)
{
+ using _Out = ostreambuf_iterator<_CharT, _Traits>;
using period = typename _Period::type;
- char __buf[sizeof("[/]s") + 2 * numeric_limits<intmax_t>::digits10];
std::basic_ostringstream<_CharT, _Traits> __s;
__s.flags(__os.flags());
__s.imbue(__os.getloc());
__s.precision(__os.precision());
__s << __d.count();
- __s << __detail::__units_suffix<period, _CharT>(__buf, sizeof(__buf));
+ __detail::__fmt_units_suffix<period, _CharT>(_Out(__s));
__os << std::move(__s).str();
return __os;
}
@@ -1074,32 +1064,16 @@ namespace __format
template<typename _Tp, typename _FormatContext>
typename _FormatContext::iterator
_M_q(const _Tp&, typename _FormatContext::iterator __out,
- _FormatContext& __ctx) const
+ _FormatContext&) const
{
// %q The duration's unit suffix
if constexpr (!chrono::__is_duration_v<_Tp>)
__throw_format_error("format error: argument is not a duration");
else
{
+ namespace __d = chrono::__detail;
using period = typename _Tp::period;
- char __buf[sizeof("[/]s") + 2 *
numeric_limits<intmax_t>::digits10];
- constexpr size_t __n = sizeof(__buf);
- auto __s = chrono::__detail::__units_suffix<period, _CharT>(__buf,
- __n);
- if constexpr (is_same_v<decltype(__s), const _CharT*>)
- return std::format_to(std::move(__out), _S_empty_spec, __s);
- else
- {
- // Suffix was written to __buf as narrow string.
- _CharT __wbuf[__n];
- size_t __len = __builtin_strlen(__buf);
- locale __loc = _M_locale(__ctx);
- auto& __ct = use_facet<ctype<_CharT>>(__loc);
- __ct.widen(__buf, __len, __wbuf);
- __wbuf[__len] = 0;
- return std::format_to(std::move(__out), _S_empty_spec,
- __wbuf);
- }
+ return __d::__fmt_units_suffix<period, _CharT>(std::move(__out));
}
}
@@ -1394,18 +1368,18 @@ namespace __format
{
if (__t._M_abbrev)
{
- __string_view __wsv;
+ string_view __sv = *__t._M_abbrev;
if constexpr (is_same_v<_CharT, char>)
- __wsv = *__t._M_abbrev;
+ return __format::__write(std::move(__out), __sv);
else
{
- string_view __sv = *__t._M_abbrev;
+ // TODO use resize_and_overwrite
basic_string<_CharT> __ws(__sv.size(), _CharT());
auto& __ct = use_facet<ctype<_CharT>>(_M_locale(__ctx));
__ct.widen(__sv.begin(), __sv.end(), __ws.data());
- __wsv = __ws;
+ __string_view __wsv = __ws;
+ return __format::__write(std::move(__out), __wsv);
}
- return __format::__write(std::move(__out), __wsv);
}
}
else if constexpr (__is_specialization_of<_Tp, __utc_leap_second>)
