[libc++][format] Implements formatter thread::id.

Since stacktrace header is WIP and it's not sure that will be done before LLVM17 update the documentation. When the header is implemented implementing the formatter is trivial, so that can be done quickly afterwards. Implements parts of: - P2693R1 Formatting thread::id and stacktrace Reviewed By: #libc, ldionne Differential Revision: https://reviews.llvm.org/D144331
llvm · Apr 8, 2023 · 88622aa · tambry · Jul 21, 2023 · mordante
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diff --git a/libcxx/docs/FeatureTestMacroTable.rst b/libcxx/docs/FeatureTestMacroTable.rst
@@ -322,6 +322,8 @@ Status
     ------------------------------------------------- -----------------
     ``__cpp_lib_expected``                            ``202202L``
     ------------------------------------------------- -----------------
+    ``__cpp_lib_formatters``                          *unimplemented*
+    ------------------------------------------------- -----------------
     ``__cpp_lib_forward_like``                        ``202207L``
     ------------------------------------------------- -----------------
     ``__cpp_lib_invoke_r``                            ``202106L``

diff --git a/libcxx/docs/ReleaseNotes.rst b/libcxx/docs/ReleaseNotes.rst
@@ -39,6 +39,7 @@ Implemented Papers
 ------------------
 - P2520R0 - ``move_iterator<T*>`` should be a random access iterator
 - P1328R1 - ``constexpr type_info::operator==()``
+- P1413R3 - Formatting ``thread::id`` (the ``stacktrace`` is not done yet)
 
 Improvements and New Features
 -----------------------------

diff --git a/libcxx/docs/Status/Cxx2b.rst b/libcxx/docs/Status/Cxx2b.rst
@@ -44,6 +44,9 @@ Paper Status
       clang doesn't issue a diagnostic for deprecated using template declarations.
    .. [#note-P2520R0] P2520R0: Libc++ implemented this paper as a DR in C++20 as well.
    .. [#note-P2711R1] P2711R1: ``join_with_view`` hasn't been done yet since this type isn't implemented yet.
+   .. [#note-P2693R1] P1413R3: The formatter for ``std::thread::id`` is implemented.
+      The formatter for ``stacktrace`` is not implemented, since ``stacktrace`` is
+      not implemented yet.
 
 .. _issues-status-cxx2b:
 

diff --git a/libcxx/docs/Status/Cxx2bPapers.csv b/libcxx/docs/Status/Cxx2bPapers.csv
@@ -113,7 +113,7 @@
 "`P2713R1 <https://wg21.link/P2713R1>`__","LWG", "Escaping improvements in ``std::format``","February 2023","","","|format|"
 "`P2675R1 <https://wg21.link/P2675R1>`__","LWG", "``format``'s width estimation is too approximate and not forward compatible","February 2023","","","|format|"
 "`P2572R1 <https://wg21.link/P2572R1>`__","LWG", "``std::format`` fill character allowances","February 2023","","","|format|"
-"`P2693R1 <https://wg21.link/P2693R1>`__","LWG", "Formatting ``thread::id`` and ``stacktrace``","February 2023","","","|format|"
+"`P2693R1 <https://wg21.link/P2693R1>`__","LWG", "Formatting ``thread::id`` and ``stacktrace``","February 2023","|Partial| [#note-P2693R1]_","","|format|"
 "`P2679R2 <https://wg21.link/P2679R2>`__","LWG", "Fixing ``std::start_lifetime_as`` for arrays","February 2023","","",""
 "`P2674R1 <https://wg21.link/P2674R1>`__","LWG", "A trait for implicit lifetime types","February 2023","","",""
 "`P2655R3 <https://wg21.link/P2655R3>`__","LWG", "``common_reference_t`` of ``reference_wrapper`` Should Be a Reference Type","February 2023","","",""

diff --git a/libcxx/docs/Status/FormatPaper.csv b/libcxx/docs/Status/FormatPaper.csv
@@ -40,5 +40,5 @@ Section,Description,Dependencies,Assignee,Status,First released version
 `[format.range.fmtstr] <https://wg21.link/format.range.fmtstr>`_,"Formatting for ranges: strings",,Mark de Wever,|In Progress|,
 `[format.range.fmtstr] <https://wg21.link/format.range.fmtstr>`_,"Formatting for ranges: strings",,Mark de Wever,|In Progress|,
 "`P2693R1 <https://wg21.link/P2693R1>`__","Formatting ``thread::id`` and ``stacktrace``"
-`[thread.thread.id] <https://wg21.link/thread.thread.id>`_,"Formatting ``thread::id``",,Mark de Wever,|In Progress|,
+`[thread.thread.id] <https://wg21.link/thread.thread.id>`_,"Formatting ``thread::id``",,Mark de Wever,|Complete|,Clang 17
 `[stacktrace.format] <https://wg21.link/stacktrace.format>`_,"Formatting ``stacktrace``",A ``<stacktrace>`` implementation,Mark de Wever,,
diff --git a/libcxx/include/__format/parser_std_format_spec.h b/libcxx/include/__format/parser_std_format_spec.h
@@ -143,6 +143,7 @@ inline constexpr __fields __fields_pointer{.__type_ = true};
 #  if _LIBCPP_STD_VER >= 23
 inline constexpr __fields __fields_tuple{.__use_range_fill_ = true};
 inline constexpr __fields __fields_range{.__use_range_fill_ = true};
+inline constexpr __fields __fields_fill_align_width{};
 #  endif
 
 enum class _LIBCPP_ENUM_VIS __alignment : uint8_t {

diff --git a/libcxx/include/__threading_support b/libcxx/include/__threading_support
@@ -643,6 +643,8 @@ private:
     _LIBCPP_INLINE_VISIBILITY
     __thread_id(__libcpp_thread_id __id) : __id_(__id) {}
 
+    _LIBCPP_HIDE_FROM_ABI friend __libcpp_thread_id __get_underlying_id(const __thread_id __id) { return __id.__id_; }
+
     friend __thread_id this_thread::get_id() _NOEXCEPT;
     friend class _LIBCPP_TYPE_VIS thread;
     friend struct _LIBCPP_TEMPLATE_VIS hash<__thread_id>;

diff --git a/libcxx/include/thread b/libcxx/include/thread
@@ -64,6 +64,9 @@ template<class charT, class traits>
 basic_ostream<charT, traits>&
 operator<<(basic_ostream<charT, traits>& out, thread::id id);
 
+template<class charT>
+struct formatter<thread::id, charT>;
+
 namespace this_thread
 {
 
@@ -84,11 +87,18 @@ void sleep_for(const chrono::duration<Rep, Period>& rel_time);
 */
 
 #include <__assert> // all public C++ headers provide the assertion handler
+#include <__availability>
 #include <__chrono/steady_clock.h>
 #include <__chrono/time_point.h>
+#include <__concepts/arithmetic.h>
 #include <__condition_variable/condition_variable.h>
 #include <__config>
 #include <__exception/terminate.h>
+#include <__format/concepts.h>
+#include <__format/format_parse_context.h>
+#include <__format/formatter.h>
+#include <__format/formatter_integral.h>
+#include <__format/parser_std_format_spec.h>
 #include <__functional/hash.h>
 #include <__memory/addressof.h>
 #include <__memory/unique_ptr.h>
@@ -224,6 +234,45 @@ basic_ostream<_CharT, _Traits>&
 operator<<(basic_ostream<_CharT, _Traits>& __os, __thread_id __id)
 {return __os << __id.__id_;}
 
+#if _LIBCPP_STD_VER >= 23
+template <__fmt_char_type _CharT>
+struct _LIBCPP_TEMPLATE_VIS formatter<__thread_id, _CharT> {
+  public:
+    _LIBCPP_HIDE_FROM_ABI constexpr auto parse(basic_format_parse_context<_CharT>& __parse_ctx)
+        -> decltype(__parse_ctx.begin()) {
+        return __parser_.__parse(__parse_ctx, __format_spec::__fields_fill_align_width);
+    }
+
+    _LIBCPP_HIDE_FROM_ABI auto format(__thread_id __id, auto& __ctx) const -> decltype(__ctx.out()) {
+        // In __threading_support __libcpp_thread_id is either a
+        // unsigned long long or a pthread_t.
+        //
+        // The type of pthread_t is left unspecified in POSIX so it can be any
+        // type. The most logical types are an integral or pointer.
+        // On Linux systems pthread_t is an unsigned long long.
+        // On Apple systems pthread_t is a pointer type.
+        //
+        // Note the output should match what the stream operator does. Since
+        // the ostream operator has been shipped years before this formatter
+        // was added to the Standard, this formatter does what the stream
+        // operator does. This may require platform specific changes.
+
+        using _Tp = decltype(__get_underlying_id(__id));
+        using _Cp = conditional_t<integral<_Tp>, _Tp, conditional_t<is_pointer_v<_Tp>, uintptr_t, void>>;
+        static_assert(!is_same_v<_Cp, void>, "unsupported thread::id type, please file a bug report");
+
+        __format_spec::__parsed_specifications<_CharT> __specs = __parser_.__get_parsed_std_specifications(__ctx);
+        if constexpr (is_pointer_v<_Tp>) {
+          __specs.__std_.__alternate_form_ = true;
+          __specs.__std_.__type_           = __format_spec::__type::__hexadecimal_lower_case;
+        }
+        return __formatter::__format_integer(reinterpret_cast<_Cp>(__get_underlying_id(__id)), __ctx, __specs);
+    }
+
+    __format_spec::__parser<_CharT> __parser_{.__alignment_ = __format_spec::__alignment::__right};
+};
+#endif // _LIBCPP_STD_VER >= 23
+
 class _LIBCPP_TYPE_VIS thread
 {
     __libcpp_thread_t __t_;

diff --git a/libcxx/include/version b/libcxx/include/version
@@ -85,6 +85,7 @@ __cpp_lib_execution                                     201902L <execution>
 __cpp_lib_expected                                      202202L <expected>
 __cpp_lib_filesystem                                    201703L <filesystem>
 __cpp_lib_format                                        202106L <format>
+__cpp_lib_formatters                                    202302L <stacktrace> <thread>
 __cpp_lib_forward_like                                  202207L <utility>
 __cpp_lib_gcd_lcm                                       201606L <numeric>
 __cpp_lib_generic_associative_lookup                    201304L <map> <set>
@@ -397,6 +398,9 @@ __cpp_lib_void_t                                        201411L <type_traits>
 # define __cpp_lib_constexpr_memory                     202202L
 # define __cpp_lib_constexpr_typeinfo                   202106L
 # define __cpp_lib_expected                             202202L
+# if !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_format) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT)
+// #   define __cpp_lib_formatters                         202302L
+# endif
 # define __cpp_lib_forward_like                         202207L
 # define __cpp_lib_invoke_r                             202106L
 # define __cpp_lib_is_scoped_enum                       202011L

diff --git a/libcxx/test/libcxx/transitive_includes/cxx03.csv b/libcxx/test/libcxx/transitive_includes/cxx03.csv
@@ -829,6 +829,7 @@ system_error stdexcept
 system_error string
 system_error type_traits
 system_error version
+thread array
 thread chrono
 thread compare
 thread cstddef
@@ -838,11 +839,15 @@ thread ctime
 thread functional
 thread iosfwd
 thread limits
+thread locale
 thread new
 thread ratio
+thread string
+thread string_view
 thread system_error
 thread tuple
 thread type_traits
+thread vector
 thread version
 tuple compare
 tuple cstddef

diff --git a/libcxx/test/libcxx/transitive_includes/cxx11.csv b/libcxx/test/libcxx/transitive_includes/cxx11.csv
@@ -830,6 +830,7 @@ system_error stdexcept
 system_error string
 system_error type_traits
 system_error version
+thread array
 thread chrono
 thread compare
 thread cstddef
@@ -839,11 +840,15 @@ thread ctime
 thread functional
 thread iosfwd
 thread limits
+thread locale
 thread new
 thread ratio
+thread string
+thread string_view
 thread system_error
 thread tuple
 thread type_traits
+thread vector
 thread version
 tuple compare
 tuple cstddef

diff --git a/libcxx/test/libcxx/transitive_includes/cxx14.csv b/libcxx/test/libcxx/transitive_includes/cxx14.csv
@@ -832,6 +832,7 @@ system_error stdexcept
 system_error string
 system_error type_traits
 system_error version
+thread array
 thread chrono
 thread compare
 thread cstddef
@@ -841,11 +842,15 @@ thread ctime
 thread functional
 thread iosfwd
 thread limits
+thread locale
 thread new
 thread ratio
+thread string
+thread string_view
 thread system_error
 thread tuple
 thread type_traits
+thread vector
 thread version
 tuple compare
 tuple cstddef

diff --git a/libcxx/test/libcxx/transitive_includes/cxx17.csv b/libcxx/test/libcxx/transitive_includes/cxx17.csv
@@ -832,6 +832,7 @@ system_error stdexcept
 system_error string
 system_error type_traits
 system_error version
+thread array
 thread chrono
 thread compare
 thread cstddef
@@ -841,11 +842,15 @@ thread ctime
 thread functional
 thread iosfwd
 thread limits
+thread locale
 thread new
 thread ratio
+thread string
+thread string_view
 thread system_error
 thread tuple
 thread type_traits
+thread vector
 thread version
 tuple compare
 tuple cstddef

diff --git a/libcxx/test/libcxx/transitive_includes/cxx20.csv b/libcxx/test/libcxx/transitive_includes/cxx20.csv
@@ -838,19 +838,26 @@ system_error stdexcept
 system_error string
 system_error type_traits
 system_error version
+thread array
 thread compare
 thread cstddef
 thread cstdint
+thread cstdlib
 thread cstring
 thread ctime
 thread functional
 thread iosfwd
 thread limits
+thread locale
 thread new
 thread ratio
+thread stdexcept
+thread string
+thread string_view
 thread system_error
 thread tuple
 thread type_traits
+thread vector
 thread version
 tuple compare
 tuple cstddef

diff --git a/libcxx/test/libcxx/transitive_includes/cxx2b.csv b/libcxx/test/libcxx/transitive_includes/cxx2b.csv
@@ -584,14 +584,22 @@ system_error limits
 system_error stdexcept
 system_error string
 system_error version
+thread array
 thread compare
 thread cstddef
+thread cstdint
+thread cstdlib
 thread ctime
 thread iosfwd
 thread limits
+thread locale
 thread ratio
+thread stdexcept
+thread string
+thread string_view
 thread system_error
 thread tuple
+thread vector
 thread version
 tuple compare
 tuple cstddef

diff --git a/...td/language.support/support.limits/support.limits.general/thread.version.compile.pass.cpp b/...td/language.support/support.limits/support.limits.general/thread.version.compile.pass.cpp
@@ -17,33 +17,50 @@
 
 // Test the feature test macros defined by <thread>
 
-/*  Constant             Value
-    __cpp_lib_jthread    201911L [C++20]
+/*  Constant                Value
+    __cpp_lib_formatters    202302L [C++2b]
+    __cpp_lib_jthread       201911L [C++20]
 */
 
 #include <thread>
 #include "test_macros.h"
 
 #if TEST_STD_VER < 14
 
+# ifdef __cpp_lib_formatters
+#   error "__cpp_lib_formatters should not be defined before c++2b"
+# endif
+
 # ifdef __cpp_lib_jthread
 #   error "__cpp_lib_jthread should not be defined before c++20"
 # endif
 
 #elif TEST_STD_VER == 14
 
+# ifdef __cpp_lib_formatters
+#   error "__cpp_lib_formatters should not be defined before c++2b"
+# endif
+
 # ifdef __cpp_lib_jthread
 #   error "__cpp_lib_jthread should not be defined before c++20"
 # endif
 
 #elif TEST_STD_VER == 17
 
+# ifdef __cpp_lib_formatters
+#   error "__cpp_lib_formatters should not be defined before c++2b"
+# endif
+
 # ifdef __cpp_lib_jthread
 #   error "__cpp_lib_jthread should not be defined before c++20"
 # endif
 
 #elif TEST_STD_VER == 20
 
+# ifdef __cpp_lib_formatters
+#   error "__cpp_lib_formatters should not be defined before c++2b"
+# endif
+
 # if !defined(_LIBCPP_VERSION)
 #   ifndef __cpp_lib_jthread
 #     error "__cpp_lib_jthread should be defined in c++20"
@@ -59,6 +76,19 @@
 
 #elif TEST_STD_VER > 20
 
+# if !defined(_LIBCPP_VERSION)
+#   ifndef __cpp_lib_formatters
+#     error "__cpp_lib_formatters should be defined in c++2b"
+#   endif
+#   if __cpp_lib_formatters != 202302L
+#     error "__cpp_lib_formatters should have the value 202302L in c++2b"
+#   endif
+# else // _LIBCPP_VERSION
+#   ifdef __cpp_lib_formatters
+#     error "__cpp_lib_formatters should not be defined because it is unimplemented in libc++!"
+#   endif
+# endif
+
 # if !defined(_LIBCPP_VERSION)
 #   ifndef __cpp_lib_jthread
 #     error "__cpp_lib_jthread should be defined in c++2b"