Implement P3107R5 optimized <print>

benchmarks/CMakeLists.txt

@@ -109,6 +109,7 @@ function(add_benchmark name)
 endfunction()
 
 add_benchmark(bitset_to_string src/bitset_to_string.cpp)
+add_benchmark(efficient_nonlocking_print src/efficient_nonlocking_print.cpp)
 add_benchmark(find_and_count src/find_and_count.cpp)
 add_benchmark(find_first_of src/find_first_of.cpp)
 add_benchmark(iota src/iota.cpp)

benchmarks/src/efficient_nonlocking_print.cpp

@@ -0,0 +1,44 @@
+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+// This benchmark inherently prints many lines to stdout. To view its results, run it with these options:
+// --benchmark_out=efficient_nonlocking_print.log --benchmark_out_format=console
+
+#include <benchmark/benchmark.h>
+#include <cstdio>
+#include <format>
+#include <print>
+#include <string>
+#include <string_view>
+#include <utility>
+
+namespace {
+    using PrintType = void (*)(FILE*, std::string_view, std::format_args);
+
+    template <PrintType PrintFunction>
+    void BM_vprint(benchmark::State& state) {
+        for (auto _ : state) {
+            PrintFunction(stdout, "Hello cool I am going to print as unicode\n", std::make_format_args());
+        }
+    }
+    BENCHMARK(BM_vprint<&std::vprint_unicode>);
+    BENCHMARK(BM_vprint<&std::vprint_unicode_buffered>);
+
+    template <PrintType PrintFunction>
+    void BM_vprint_complex(benchmark::State& state) {
+        const int i           = 42;
+        const std::string str = "Hello world!!!!!!!!!!!!!!!!!!!!!!!!";
+        const double f        = -902.16283758;
+        const std::pair<int, double> p{16, 2.073f};
+        for (auto _ : state) {
+            PrintFunction(stdout,
+                "Hello cool I am going to print as unicode!! {:X}, {}, {:a}, "
+                "I am a big string, lots of words, multiple {} formats\n",
+                std::make_format_args(i, str, f, p));
+        }
+    }
+    BENCHMARK(BM_vprint_complex<&std::vprint_unicode>);
+    BENCHMARK(BM_vprint_complex<&std::vprint_unicode_buffered>);
+} // namespace
+
+BENCHMARK_MAIN();

stl/inc/__msvc_formatter.hpp

@@ -90,6 +90,9 @@ enum class _Basic_format_arg_type : uint8_t {
 static_assert(static_cast<int>(_Basic_format_arg_type::_Custom_type) < 16, "must fit in 4-bit bitfield");
 
 #if _HAS_CXX23
+_EXPORT_STD template <class _Ty>
+constexpr bool enable_nonlocking_formatter_optimization = false;
+
 _NODISCARD consteval bool _Is_debug_enabled_fmt_type(_Basic_format_arg_type _Ty) {
     return _Ty == _Basic_format_arg_type::_Char_type || _Ty == _Basic_format_arg_type::_CString_type
         || _Ty == _Basic_format_arg_type::_String_type;
@@ -170,7 +173,16 @@ struct _Formatter_base {
 };
 _FMT_P2286_END
 
+#if _HAS_CXX23
+#define _FORMAT_SPECIALIZE_NONLOCKING_FOR(_Type) \
+    template <>                                  \
+    inline constexpr bool enable_nonlocking_formatter_optimization<_Type> = true;
+#else // ^^^ _HAS_CXX23 / !_HAS_CXX23 vvv
+#define _FORMAT_SPECIALIZE_NONLOCKING_FOR(_Type)
+#endif // ^^^ !_HAS_CXX23 ^^^
+
 #define _FORMAT_SPECIALIZE_FOR(_Type, _ArgType) \
+    _FORMAT_SPECIALIZE_NONLOCKING_FOR(_Type)    \
     template <_Format_supported_charT _CharT>   \
     struct formatter<_Type, _CharT> : _Formatter_base<_Type, _CharT, _ArgType> {}
 
@@ -193,6 +205,7 @@ _FORMAT_SPECIALIZE_FOR(signed char, _Basic_format_arg_type::_Int_type);
 _FORMAT_SPECIALIZE_FOR(unsigned char, _Basic_format_arg_type::_UInt_type);
 
 #undef _FORMAT_SPECIALIZE_FOR
+#undef _FORMAT_SPECIALIZE_NONLOCKING_FOR
 
 // not using the macro because we'd like to add 'set_debug_format' member function in C++23 mode
 template <_Format_supported_charT _CharT>
@@ -361,6 +374,32 @@ struct formatter<pair<_Ty1, _Ty2>, _CharT>;
 
 template <_Format_supported_charT _CharT, class... _Types>
 struct formatter<tuple<_Types...>, _CharT>;
+
+template <_Format_supported_charT _CharT>
+constexpr bool enable_nonlocking_formatter_optimization<_CharT> = true;
+
+template <_Format_supported_charT _CharT>
+constexpr bool enable_nonlocking_formatter_optimization<_CharT*> = true;
+
+template <_Format_supported_charT _CharT>
+constexpr bool enable_nonlocking_formatter_optimization<const _CharT*> = true;
+
+template <_Format_supported_charT _CharT, size_t _Nx>
+constexpr bool enable_nonlocking_formatter_optimization<_CharT[_Nx]> = true;
+
+template <_Format_supported_charT _CharT, class _Traits, class _Allocator>
+constexpr bool enable_nonlocking_formatter_optimization<basic_string<_CharT, _Traits, _Allocator>> = true;
+
+template <_Format_supported_charT _CharT, class _Traits>
+constexpr bool enable_nonlocking_formatter_optimization<basic_string_view<_CharT, _Traits>> = true;
+
+template <class _Ty1, class _Ty2>
+constexpr bool enable_nonlocking_formatter_optimization<pair<_Ty1, _Ty2>> =
+    enable_nonlocking_formatter_optimization<_Ty1> && enable_nonlocking_formatter_optimization<_Ty2>;
+
+template <class... _Ts>
+constexpr bool enable_nonlocking_formatter_optimization<tuple<_Ts...>> =
+    (enable_nonlocking_formatter_optimization<_Ts> && ...);
 #endif // _HAS_CXX23
 _STD_END
 

stl/inc/chrono

@@ -5805,62 +5805,158 @@ template <class _Rep, class _Period, _Format_supported_charT _CharT>
 struct formatter<_CHRONO duration<_Rep, _Period>, _CharT>
     : _Fill_tm_formatter<_CHRONO duration<_Rep, _Period>, _CharT> {};
 
+#if _HAS_CXX23
+template <class _Rep, class _Period>
+constexpr bool enable_nonlocking_formatter_optimization<_CHRONO duration<_Rep, _Period>> =
+    enable_nonlocking_formatter_optimization<_Rep>;
+#endif // _HAS_CXX23
+
 template <_Format_supported_charT _CharT>
 struct formatter<_CHRONO day, _CharT> : _Fill_tm_formatter<_CHRONO day, _CharT> {};
 
+#if _HAS_CXX23
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<_CHRONO day> = true;
+#endif // _HAS_CXX23
+
 template <_Format_supported_charT _CharT>
 struct formatter<_CHRONO month, _CharT> : _Fill_tm_formatter<_CHRONO month, _CharT> {};
 
+#if _HAS_CXX23
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<_CHRONO month> = true;
+#endif // _HAS_CXX23
+
 template <_Format_supported_charT _CharT>
 struct formatter<_CHRONO year, _CharT> : _Fill_tm_formatter<_CHRONO year, _CharT> {};
 
+#if _HAS_CXX23
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<_CHRONO year> = true;
+#endif // _HAS_CXX23
+
 template <_Format_supported_charT _CharT>
 struct formatter<_CHRONO weekday, _CharT> : _Fill_tm_formatter<_CHRONO weekday, _CharT> {};
 
+#if _HAS_CXX23
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<_CHRONO weekday> = true;
+#endif // _HAS_CXX23
+
 template <_Format_supported_charT _CharT>
 struct formatter<_CHRONO weekday_indexed, _CharT> : _Fill_tm_formatter<_CHRONO weekday_indexed, _CharT> {};
 
+#if _HAS_CXX23
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<_CHRONO weekday_indexed> = true;
+#endif // _HAS_CXX23
+
 template <_Format_supported_charT _CharT>
 struct formatter<_CHRONO weekday_last, _CharT> : _Fill_tm_formatter<_CHRONO weekday_last, _CharT> {};
 
+#if _HAS_CXX23
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<_CHRONO weekday_last> = true;
+#endif // _HAS_CXX23
+
 template <_Format_supported_charT _CharT>
 struct formatter<_CHRONO month_day, _CharT> : _Fill_tm_formatter<_CHRONO month_day, _CharT> {};
 
+#if _HAS_CXX23
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<_CHRONO month_day> = true;
+#endif // _HAS_CXX23
+
 template <_Format_supported_charT _CharT>
 struct formatter<_CHRONO month_day_last, _CharT> : _Fill_tm_formatter<_CHRONO month_day_last, _CharT> {};
 
+#if _HAS_CXX23
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<_CHRONO month_day_last> = true;
+#endif // _HAS_CXX23
+
 template <_Format_supported_charT _CharT>
 struct formatter<_CHRONO month_weekday, _CharT> : _Fill_tm_formatter<_CHRONO month_weekday, _CharT> {};
 
+#if _HAS_CXX23
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<_CHRONO month_weekday> = true;
+#endif // _HAS_CXX23
+
 template <_Format_supported_charT _CharT>
 struct formatter<_CHRONO month_weekday_last, _CharT> : _Fill_tm_formatter<_CHRONO month_weekday_last, _CharT> {};
 
+#if _HAS_CXX23
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<_CHRONO month_weekday_last> = true;
+#endif // _HAS_CXX23
+
 template <_Format_supported_charT _CharT>
 struct formatter<_CHRONO year_month, _CharT> : _Fill_tm_formatter<_CHRONO year_month, _CharT> {};
 
+#if _HAS_CXX23
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<_CHRONO year_month> = true;
+#endif // _HAS_CXX23
+
 template <_Format_supported_charT _CharT>
 struct formatter<_CHRONO year_month_day, _CharT> : _Fill_tm_formatter<_CHRONO year_month_day, _CharT> {};
 
+#if _HAS_CXX23
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<_CHRONO year_month_day> = true;
+#endif // _HAS_CXX23
+
 template <_Format_supported_charT _CharT>
 struct formatter<_CHRONO year_month_day_last, _CharT> : _Fill_tm_formatter<_CHRONO year_month_day_last, _CharT> {};
 
+#if _HAS_CXX23
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<_CHRONO year_month_day_last> = true;
+#endif // _HAS_CXX23
+
 template <_Format_supported_charT _CharT>
 struct formatter<_CHRONO year_month_weekday, _CharT> : _Fill_tm_formatter<_CHRONO year_month_weekday, _CharT> {};
 
+#if _HAS_CXX23
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<_CHRONO year_month_weekday> = true;
+#endif // _HAS_CXX23
+
 template <_Format_supported_charT _CharT>
 struct formatter<_CHRONO year_month_weekday_last, _CharT>
     : _Fill_tm_formatter<_CHRONO year_month_weekday_last, _CharT> {};
 
+#if _HAS_CXX23
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<_CHRONO year_month_weekday_last> = true;
+#endif // _HAS_CXX23
+
 template <class _Rep, class _Period, _Format_supported_charT _CharT>
 struct formatter<_CHRONO hh_mm_ss<_CHRONO duration<_Rep, _Period>>, _CharT>
     : _Fill_tm_formatter<_CHRONO hh_mm_ss<_CHRONO duration<_Rep, _Period>>, _CharT> {};
 
+#if _HAS_CXX23
+template <class _Rep, class _Period>
+constexpr bool enable_nonlocking_formatter_optimization<_CHRONO hh_mm_ss<_CHRONO duration<_Rep, _Period>>> = true;
+#endif // _HAS_CXX23
+
 template <_Format_supported_charT _CharT>
 struct formatter<_CHRONO sys_info, _CharT> : _Fill_tm_formatter<_CHRONO sys_info, _CharT> {};
 
+#if _HAS_CXX23
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<_CHRONO sys_info> = true;
+#endif // _HAS_CXX23
+
 template <_Format_supported_charT _CharT>
 struct formatter<_CHRONO local_info, _CharT> : _Fill_tm_formatter<_CHRONO local_info, _CharT> {};
 
+#if _HAS_CXX23
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<_CHRONO local_info> = true;
+#endif // _HAS_CXX23
+
 template <class _Duration, _Format_supported_charT _CharT>
 struct formatter<_CHRONO sys_time<_Duration>, _CharT> {
     constexpr auto parse(basic_format_parse_context<_CharT>& _Parse_ctx) {
@@ -5876,6 +5972,11 @@ private:
     _CHRONO _Chrono_formatter<_CharT> _Impl{_STATICALLY_WIDEN(_CharT, "UTC")};
 };
 
+#if _HAS_CXX23
+template <class _Duration>
+constexpr bool enable_nonlocking_formatter_optimization<_CHRONO sys_time<_Duration>> = true;
+#endif // _HAS_CXX23
+
 template <class _Duration, _Format_supported_charT _CharT>
 struct formatter<_CHRONO utc_time<_Duration>, _CharT> {
     constexpr auto parse(basic_format_parse_context<_CharT>& _Parse_ctx) {
@@ -5892,6 +5993,11 @@ private:
     _CHRONO _Chrono_formatter<_CharT> _Impl{_STATICALLY_WIDEN(_CharT, "UTC")};
 };
 
+#if _HAS_CXX23
+template <class _Duration>
+constexpr bool enable_nonlocking_formatter_optimization<_CHRONO utc_time<_Duration>> = true;
+#endif // _HAS_CXX23
+
 template <class _Duration, _Format_supported_charT _CharT>
 struct formatter<_CHRONO tai_time<_Duration>, _CharT> {
     constexpr auto parse(basic_format_parse_context<_CharT>& _Parse_ctx) {
@@ -5911,6 +6017,11 @@ private:
     _CHRONO _Chrono_formatter<_CharT> _Impl{_STATICALLY_WIDEN(_CharT, "TAI")};
 };
 
+#if _HAS_CXX23
+template <class _Duration>
+constexpr bool enable_nonlocking_formatter_optimization<_CHRONO tai_time<_Duration>> = true;
+#endif // _HAS_CXX23
+
 template <class _Duration, _Format_supported_charT _CharT>
 struct formatter<_CHRONO gps_time<_Duration>, _CharT> {
     constexpr auto parse(basic_format_parse_context<_CharT>& _Parse_ctx) {
@@ -5930,6 +6041,11 @@ private:
     _CHRONO _Chrono_formatter<_CharT> _Impl{_STATICALLY_WIDEN(_CharT, "GPS")};
 };
 
+#if _HAS_CXX23
+template <class _Duration>
+constexpr bool enable_nonlocking_formatter_optimization<_CHRONO gps_time<_Duration>> = true;
+#endif // _HAS_CXX23
+
 template <class _Duration, _Format_supported_charT _CharT>
 struct formatter<_CHRONO file_time<_Duration>, _CharT> {
     constexpr auto parse(basic_format_parse_context<_CharT>& _Parse_ctx) {
@@ -5947,13 +6063,28 @@ private:
     _CHRONO _Chrono_formatter<_CharT> _Impl{_STATICALLY_WIDEN(_CharT, "UTC")};
 };
 
+#if _HAS_CXX23
+template <class _Duration>
+constexpr bool enable_nonlocking_formatter_optimization<_CHRONO file_time<_Duration>> = true;
+#endif // _HAS_CXX23
+
 template <class _Duration, _Format_supported_charT _CharT>
 struct formatter<_CHRONO local_time<_Duration>, _CharT> : _Fill_tm_formatter<_CHRONO local_time<_Duration>, _CharT> {};
 
+#if _HAS_CXX23
+template <class _Duration>
+constexpr bool enable_nonlocking_formatter_optimization<_CHRONO local_time<_Duration>> = true;
+#endif // _HAS_CXX23
+
 template <class _Duration, _Format_supported_charT _CharT>
 struct formatter<_CHRONO _Local_time_format_t<_Duration>, _CharT>
     : _Fill_tm_formatter<_CHRONO _Local_time_format_t<_Duration>, _CharT> {};
 
+#if _HAS_CXX23
+template <class _Duration>
+constexpr bool enable_nonlocking_formatter_optimization<_CHRONO _Local_time_format_t<_Duration>> = true;
+#endif // _HAS_CXX23
+
 template <class _Duration, class _TimeZonePtr, _Format_supported_charT _CharT>
 struct formatter<_CHRONO zoned_time<_Duration, _TimeZonePtr>, _CharT>
     : formatter<_CHRONO _Local_time_format_t<_Duration>, _CharT> {
@@ -5966,6 +6097,11 @@ struct formatter<_CHRONO zoned_time<_Duration, _TimeZonePtr>, _CharT>
     }
 };
 
+#if _HAS_CXX23
+template <class _Duration>
+constexpr bool enable_nonlocking_formatter_optimization<_CHRONO zoned_time<_Duration, const _CHRONO time_zone*>> = true;
+#endif // _HAS_CXX23
+
 namespace chrono {
     template <class _Duration>
     _NODISCARD string nonexistent_local_time::_Make_string(const local_time<_Duration>& _Tp, const local_info& _Info) {