[libc++] Granularize system_error.

Reviewed By: #libc, philnik

Differential Revision: https://reviews.llvm.org/D147853

libcxx/docs/ReleaseNotes.rst

@@ -63,8 +63,8 @@ Deprecations and Removals
   includes are removed based on the language version used. Incidental transitive
   inclusions of the following headers have been removed:
 
-  - C++2b: ``atomic``, ``bit``, ``cstdint``, ``cstdlib``, ``cstring``, ``initializer_list``, ``new``, ``stdexcept``,
-           ``type_traits``, ``typeinfo``
+  - C++2b: ``atomic``, ``bit``, ``cstdint``, ``cstdlib``, ``cstring``, ``initializer_list``, ``limits``, ``new``,
+           ``stdexcept``, ``system_error``, ``type_traits``, ``typeinfo``
 
 - The headers ``<experimental/algorithm>`` and ``<experimental/functional>`` have been removed, since all the contents
   have been implemented in namespace ``std`` for at least two releases.

libcxx/include/CMakeLists.txt

@@ -589,6 +589,10 @@ set(files
   __support/xlocale/__nop_locale_mgmt.h
   __support/xlocale/__posix_l_fallback.h
   __support/xlocale/__strtonum_fallback.h
+  __system_error/error_category.h
+  __system_error/error_code.h
+  __system_error/error_condition.h
+  __system_error/system_error.h
   __thread/poll_with_backoff.h
   __thread/timed_backoff_policy.h
   __threading_support

libcxx/include/__condition_variable/condition_variable.h

@@ -15,12 +15,12 @@
 #include <__config>
 #include <__mutex/mutex.h>
 #include <__mutex/unique_lock.h>
+#include <__system_error/system_error.h>
 #include <__threading_support>
 #include <__type_traits/enable_if.h>
 #include <__type_traits/is_floating_point.h>
 #include <__utility/move.h>
 #include <ratio>
-#include <system_error>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header

libcxx/include/__filesystem/directory_entry.h

@@ -12,6 +12,7 @@
 
 #include <__availability>
 #include <__chrono/time_point.h>
+#include <__compare/ordering.h>
 #include <__config>
 #include <__errc>
 #include <__filesystem/file_status.h>
@@ -21,10 +22,11 @@
 #include <__filesystem/operations.h>
 #include <__filesystem/path.h>
 #include <__filesystem/perms.h>
+#include <__system_error/error_code.h>
+#include <__utility/move.h>
 #include <__utility/unreachable.h>
 #include <cstdint>
 #include <iosfwd>
-#include <system_error>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header

libcxx/include/__filesystem/directory_iterator.h

@@ -20,8 +20,9 @@
 #include <__memory/shared_ptr.h>
 #include <__ranges/enable_borrowed_range.h>
 #include <__ranges/enable_view.h>
+#include <__system_error/error_code.h>
+#include <__utility/move.h>
 #include <cstddef>
-#include <system_error>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header

libcxx/include/__filesystem/filesystem_error.h

@@ -14,11 +14,13 @@
 #include <__config>
 #include <__filesystem/path.h>
 #include <__memory/shared_ptr.h>
+#include <__system_error/error_code.h>
+#include <__system_error/system_error.h>
 #include <__utility/forward.h>
 #include <__verbose_abort>
 #include <iosfwd>
 #include <new>
-#include <system_error>
+#include <string>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header

libcxx/include/__filesystem/operations.h

@@ -21,8 +21,8 @@
 #include <__filesystem/perm_options.h>
 #include <__filesystem/perms.h>
 #include <__filesystem/space_info.h>
+#include <__system_error/error_code.h>
 #include <cstdint>
-#include <system_error>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header

libcxx/include/__filesystem/recursive_directory_iterator.h

@@ -19,8 +19,9 @@
 #include <__memory/shared_ptr.h>
 #include <__ranges/enable_borrowed_range.h>
 #include <__ranges/enable_view.h>
+#include <__system_error/error_code.h>
+#include <__utility/move.h>
 #include <cstddef>
-#include <system_error>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header

libcxx/include/__mutex/unique_lock.h

@@ -14,8 +14,9 @@
 #include <__config>
 #include <__memory/addressof.h>
 #include <__mutex/tag_types.h>
+#include <__system_error/system_error.h>
 #include <__utility/swap.h>
-#include <system_error>
+#include <cerrno>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header

libcxx/include/__system_error/error_category.h

@@ -0,0 +1,81 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___SYSTEM_ERROR_ERROR_CATEGORY_H
+#define _LIBCPP___SYSTEM_ERROR_ERROR_CATEGORY_H
+
+#include <__compare/ordering.h>
+#include <__config>
+#include <string>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+class _LIBCPP_TYPE_VIS error_condition;
+class _LIBCPP_TYPE_VIS error_code;
+
+class _LIBCPP_HIDDEN __do_message;
+
+class _LIBCPP_TYPE_VIS error_category
+{
+public:
+    virtual ~error_category() _NOEXCEPT;
+
+#if defined(_LIBCPP_ERROR_CATEGORY_DEFINE_LEGACY_INLINE_FUNCTIONS)
+    error_category() noexcept;
+#else
+    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_CONSTEXPR_SINCE_CXX14 error_category() _NOEXCEPT = default;
+#endif
+    error_category(const error_category&) = delete;
+    error_category& operator=(const error_category&) = delete;
+
+    virtual const char* name() const _NOEXCEPT = 0;
+    virtual error_condition default_error_condition(int __ev) const _NOEXCEPT;
+    virtual bool equivalent(int __code, const error_condition& __condition) const _NOEXCEPT;
+    virtual bool equivalent(const error_code& __code, int __condition) const _NOEXCEPT;
+    virtual string message(int __ev) const = 0;
+
+    _LIBCPP_INLINE_VISIBILITY
+    bool operator==(const error_category& __rhs) const _NOEXCEPT {return this == &__rhs;}
+
+#if _LIBCPP_STD_VER >= 20
+
+    _LIBCPP_HIDE_FROM_ABI
+    strong_ordering operator<=>(const error_category& __rhs) const noexcept {return compare_three_way()(this, std::addressof(__rhs));}
+
+#else // _LIBCPP_STD_VER >= 20
+
+    _LIBCPP_INLINE_VISIBILITY
+    bool operator!=(const error_category& __rhs) const _NOEXCEPT {return !(*this == __rhs);}
+
+    _LIBCPP_INLINE_VISIBILITY
+    bool operator< (const error_category& __rhs) const _NOEXCEPT {return this < &__rhs;}
+
+#endif // _LIBCPP_STD_VER >= 20
+
+    friend class _LIBCPP_HIDDEN __do_message;
+};
+
+class _LIBCPP_HIDDEN __do_message
+    : public error_category
+{
+public:
+    string message(int __ev) const override;
+};
+
+_LIBCPP_FUNC_VIS const error_category& generic_category() _NOEXCEPT;
+_LIBCPP_FUNC_VIS const error_category& system_category() _NOEXCEPT;
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___SYSTEM_ERROR_ERROR_CATEGORY_H

libcxx/include/__system_error/error_code.h

@@ -0,0 +1,191 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___SYSTEM_ERROR_ERROR_CODE_H
+#define _LIBCPP___SYSTEM_ERROR_ERROR_CODE_H
+
+#include <__compare/ordering.h>
+#include <__config>
+#include <__errc>
+#include <__functional/hash.h>
+#include <__functional/unary_function.h>
+#include <__system_error/error_category.h>
+#include <__system_error/error_condition.h>
+#include <cstddef>
+#include <string>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <class _Tp>
+struct _LIBCPP_TEMPLATE_VIS is_error_code_enum
+    : public false_type {};
+
+#if _LIBCPP_STD_VER >= 17
+template <class _Tp>
+inline constexpr bool is_error_code_enum_v = is_error_code_enum<_Tp>::value;
+#endif
+
+namespace __adl_only {
+    // Those cause ADL to trigger but they are not viable candidates,
+    // so they are never actually selected.
+    void make_error_code() = delete;
+} // namespace __adl_only
+
+class _LIBCPP_TYPE_VIS error_code
+{
+    int __val_;
+    const error_category* __cat_;
+public:
+    _LIBCPP_INLINE_VISIBILITY
+    error_code() _NOEXCEPT : __val_(0), __cat_(&system_category()) {}
+
+    _LIBCPP_INLINE_VISIBILITY
+    error_code(int __val, const error_category& __cat) _NOEXCEPT
+        : __val_(__val), __cat_(&__cat) {}
+
+    template <class _Ep>
+        _LIBCPP_INLINE_VISIBILITY
+        error_code(_Ep __e,
+                   typename enable_if<is_error_code_enum<_Ep>::value>::type* = nullptr
+                                                                     ) _NOEXCEPT
+            {
+                using __adl_only::make_error_code;
+                *this = make_error_code(__e);
+            }
+
+    _LIBCPP_INLINE_VISIBILITY
+    void assign(int __val, const error_category& __cat) _NOEXCEPT
+    {
+        __val_ = __val;
+        __cat_ = &__cat;
+    }
+
+    template <class _Ep>
+        _LIBCPP_INLINE_VISIBILITY
+        typename enable_if
+        <
+            is_error_code_enum<_Ep>::value,
+            error_code&
+        >::type
+        operator=(_Ep __e) _NOEXCEPT
+            {
+                using __adl_only::make_error_code;
+                *this = make_error_code(__e);
+                return *this;
+            }
+
+    _LIBCPP_INLINE_VISIBILITY
+    void clear() _NOEXCEPT
+    {
+        __val_ = 0;
+        __cat_ = &system_category();
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    int value() const _NOEXCEPT {return __val_;}
+
+    _LIBCPP_INLINE_VISIBILITY
+    const error_category& category() const _NOEXCEPT {return *__cat_;}
+
+    _LIBCPP_INLINE_VISIBILITY
+    error_condition default_error_condition() const _NOEXCEPT
+        {return __cat_->default_error_condition(__val_);}
+
+    string message() const;
+
+    _LIBCPP_INLINE_VISIBILITY
+    explicit operator bool() const _NOEXCEPT {return __val_ != 0;}
+};
+
+inline _LIBCPP_INLINE_VISIBILITY
+error_code
+make_error_code(errc __e) _NOEXCEPT
+{
+    return error_code(static_cast<int>(__e), generic_category());
+}
+
+inline _LIBCPP_INLINE_VISIBILITY
+bool
+operator==(const error_code& __x, const error_code& __y) _NOEXCEPT
+{
+    return __x.category() == __y.category() && __x.value() == __y.value();
+}
+
+inline _LIBCPP_INLINE_VISIBILITY
+bool
+operator==(const error_code& __x, const error_condition& __y) _NOEXCEPT
+{
+    return __x.category().equivalent(__x.value(), __y)
+        || __y.category().equivalent(__x, __y.value());
+}
+
+#if _LIBCPP_STD_VER <= 17
+inline _LIBCPP_INLINE_VISIBILITY
+bool
+operator==(const error_condition& __x, const error_code& __y) _NOEXCEPT
+{
+    return __y == __x;
+}
+#endif
+
+#if _LIBCPP_STD_VER <= 17
+
+inline _LIBCPP_INLINE_VISIBILITY
+bool
+operator!=(const error_code& __x, const error_code& __y) _NOEXCEPT
+{return !(__x == __y);}
+
+inline _LIBCPP_INLINE_VISIBILITY
+bool
+operator!=(const error_code& __x, const error_condition& __y) _NOEXCEPT
+{return !(__x == __y);}
+
+inline _LIBCPP_INLINE_VISIBILITY
+bool
+operator!=(const error_condition& __x, const error_code& __y) _NOEXCEPT
+{return !(__x == __y);}
+
+inline _LIBCPP_INLINE_VISIBILITY
+bool
+operator<(const error_code& __x, const error_code& __y) _NOEXCEPT
+{
+    return __x.category() < __y.category()
+        || (__x.category() == __y.category() && __x.value() < __y.value());
+}
+
+#else // _LIBCPP_STD_VER <= 17
+
+inline _LIBCPP_HIDE_FROM_ABI strong_ordering
+operator<=>(const error_code& __x, const error_code& __y) noexcept
+{
+    if (auto __c = __x.category() <=> __y.category(); __c != 0)
+        return __c;
+    return __x.value() <=> __y.value();
+}
+
+#endif // _LIBCPP_STD_VER <= 17
+
+template <>
+struct _LIBCPP_TEMPLATE_VIS hash<error_code>
+    : public __unary_function<error_code, size_t>
+{
+    _LIBCPP_INLINE_VISIBILITY
+    size_t operator()(const error_code& __ec) const _NOEXCEPT
+    {
+        return static_cast<size_t>(__ec.value());
+    }
+};
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___SYSTEM_ERROR_ERROR_CODE_H

libcxx/include/__system_error/error_condition.h

@@ -0,0 +1,168 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___SYSTEM_ERROR_ERROR_CONDITION_H
+#define _LIBCPP___SYSTEM_ERROR_ERROR_CONDITION_H
+
+#include <__compare/ordering.h>
+#include <__config>
+#include <__errc>
+#include <__functional/unary_function.h>
+#include <__system_error/error_category.h>
+#include <cstddef>
+#include <string>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <class _Tp>
+struct _LIBCPP_TEMPLATE_VIS is_error_condition_enum
+    : public false_type {};
+
+#if _LIBCPP_STD_VER >= 17
+template <class _Tp>
+inline constexpr bool is_error_condition_enum_v = is_error_condition_enum<_Tp>::value;
+#endif
+
+template <>
+struct _LIBCPP_TEMPLATE_VIS is_error_condition_enum<errc>
+    : true_type { };
+
+#ifdef _LIBCPP_CXX03_LANG
+template <>
+struct _LIBCPP_TEMPLATE_VIS is_error_condition_enum<errc::__lx>
+    : true_type { };
+#endif
+
+namespace __adl_only {
+    // Those cause ADL to trigger but they are not viable candidates,
+    // so they are never actually selected.
+    void make_error_condition() = delete;
+} // namespace __adl_only
+
+class _LIBCPP_TYPE_VIS error_condition
+{
+    int __val_;
+    const error_category* __cat_;
+public:
+    _LIBCPP_INLINE_VISIBILITY
+    error_condition() _NOEXCEPT : __val_(0), __cat_(&generic_category()) {}
+
+    _LIBCPP_INLINE_VISIBILITY
+    error_condition(int __val, const error_category& __cat) _NOEXCEPT
+        : __val_(__val), __cat_(&__cat) {}
+
+    template <class _Ep>
+        _LIBCPP_INLINE_VISIBILITY
+        error_condition(_Ep __e,
+              typename enable_if<is_error_condition_enum<_Ep>::value>::type* = nullptr
+                                                                     ) _NOEXCEPT
+            {
+                using __adl_only::make_error_condition;
+                *this = make_error_condition(__e);
+            }
+
+    _LIBCPP_INLINE_VISIBILITY
+    void assign(int __val, const error_category& __cat) _NOEXCEPT
+    {
+        __val_ = __val;
+        __cat_ = &__cat;
+    }
+
+    template <class _Ep>
+        _LIBCPP_INLINE_VISIBILITY
+        typename enable_if
+        <
+            is_error_condition_enum<_Ep>::value,
+            error_condition&
+        >::type
+        operator=(_Ep __e) _NOEXCEPT
+            {
+                using __adl_only::make_error_condition;
+                *this = make_error_condition(__e);
+                return *this;
+            }
+
+    _LIBCPP_INLINE_VISIBILITY
+    void clear() _NOEXCEPT
+    {
+        __val_ = 0;
+        __cat_ = &generic_category();
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    int value() const _NOEXCEPT {return __val_;}
+
+    _LIBCPP_INLINE_VISIBILITY
+    const error_category& category() const _NOEXCEPT {return *__cat_;}
+    string message() const;
+
+    _LIBCPP_INLINE_VISIBILITY
+    explicit operator bool() const _NOEXCEPT {return __val_ != 0;}
+};
+
+inline _LIBCPP_INLINE_VISIBILITY
+error_condition
+make_error_condition(errc __e) _NOEXCEPT
+{
+    return error_condition(static_cast<int>(__e), generic_category());
+}
+
+inline _LIBCPP_INLINE_VISIBILITY
+bool
+operator==(const error_condition& __x, const error_condition& __y) _NOEXCEPT
+{
+    return __x.category() == __y.category() && __x.value() == __y.value();
+}
+
+#if _LIBCPP_STD_VER <= 17
+
+inline _LIBCPP_INLINE_VISIBILITY
+bool
+operator!=(const error_condition& __x, const error_condition& __y) _NOEXCEPT
+{return !(__x == __y);}
+
+inline _LIBCPP_INLINE_VISIBILITY
+bool
+operator<(const error_condition& __x, const error_condition& __y) _NOEXCEPT
+{
+    return __x.category() < __y.category()
+        || (__x.category() == __y.category() && __x.value() < __y.value());
+}
+
+
+#else // _LIBCPP_STD_VER <= 17
+
+inline _LIBCPP_HIDE_FROM_ABI strong_ordering
+operator<=>(const error_condition& __x, const error_condition& __y) noexcept
+{
+    if (auto __c = __x.category() <=> __y.category(); __c != 0)
+       return __c;
+    return __x.value() <=> __y.value();
+}
+
+#endif // _LIBCPP_STD_VER <= 17
+
+template <>
+struct _LIBCPP_TEMPLATE_VIS hash<error_condition>
+    : public __unary_function<error_condition, size_t>
+{
+    _LIBCPP_INLINE_VISIBILITY
+    size_t operator()(const error_condition& __ec) const _NOEXCEPT
+    {
+        return static_cast<size_t>(__ec.value());
+    }
+};
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___SYSTEM_ERROR_ERROR_CONDITION_H

libcxx/include/__system_error/system_error.h

@@ -0,0 +1,51 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___SYSTEM_ERROR_SYSTEM_ERROR_H
+#define _LIBCPP___SYSTEM_ERROR_SYSTEM_ERROR_H
+
+#include <__config>
+#include <__system_error/error_category.h>
+#include <__system_error/error_code.h>
+#include <stdexcept>
+#include <string>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+class _LIBCPP_TYPE_VIS system_error
+    : public runtime_error
+{
+    error_code __ec_;
+public:
+    system_error(error_code __ec, const string& __what_arg);
+    system_error(error_code __ec, const char* __what_arg);
+    system_error(error_code __ec);
+    system_error(int __ev, const error_category& __ecat, const string& __what_arg);
+    system_error(int __ev, const error_category& __ecat, const char* __what_arg);
+    system_error(int __ev, const error_category& __ecat);
+    system_error(const system_error&) _NOEXCEPT = default;
+    ~system_error() _NOEXCEPT override;
+
+    _LIBCPP_INLINE_VISIBILITY
+    const error_code& code() const _NOEXCEPT {return __ec_;}
+
+private:
+    static string __init(const error_code&, string);
+};
+
+_LIBCPP_NORETURN _LIBCPP_FUNC_VIS
+void __throw_system_error(int __ev, const char* __what_arg);
+
+
+_LIBCPP_END_NAMESPACE_STD
+#endif // _LIBCPP___SYSTEM_ERROR_SYSTEM_ERROR_H

libcxx/include/condition_variable

@@ -285,6 +285,7 @@ _LIBCPP_END_NAMESPACE_STD
 #  include <initializer_list>
 #  include <new>
 #  include <stdexcept>
+#  include <system_error>
 #  include <type_traits>
 #  include <typeinfo>
 #endif

libcxx/include/filesystem

@@ -468,6 +468,7 @@ inline constexpr bool std::ranges::enable_view<std::filesystem::recursive_direct
 #if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
 #  include <concepts>
 #  include <cstdlib>
+#  include <system_error>
 #endif
 
 #endif // _LIBCPP_FILESYSTEM

libcxx/include/future

@@ -367,11 +367,18 @@ template <class R, class Alloc> struct uses_allocator<packaged_task<R>, Alloc>;
 #include <__chrono/time_point.h>
 #include <__config>
 #include <__exception/exception_ptr.h>
+#include <__memory/allocator.h>
 #include <__memory/allocator_arg_t.h>
 #include <__memory/allocator_destructor.h>
+#include <__memory/allocator_traits.h>
+#include <__memory/compressed_pair.h>
+#include <__memory/pointer_traits.h>
 #include <__memory/shared_ptr.h>
 #include <__memory/unique_ptr.h>
 #include <__memory/uses_allocator.h>
+#include <__system_error/error_category.h>
+#include <__system_error/error_code.h>
+#include <__system_error/error_condition.h>
 #include <__type_traits/aligned_storage.h>
 #include <__type_traits/alignment_of.h>
 #include <__type_traits/strip_signature.h>
@@ -380,7 +387,7 @@ template <class R, class Alloc> struct uses_allocator<packaged_task<R>, Alloc>;
 #include <__utility/move.h>
 #include <mutex>
 #include <new>
-#include <system_error>
+#include <stdexcept>
 #include <thread>
 #include <version>
 
@@ -2462,6 +2469,7 @@ _LIBCPP_END_NAMESPACE_STD
 #  include <atomic>
 #  include <cstdlib>
 #  include <exception>
+#  include <system_error>
 #endif
 
 #endif // _LIBCPP_FUTURE

libcxx/include/ios

@@ -219,9 +219,12 @@ storage-class-specifier const error_category& iostream_category() noexcept;
 #include <__assert> // all public C++ headers provide the assertion handler
 #include <__ios/fpos.h>
 #include <__locale>
+#include <__system_error/error_category.h>
+#include <__system_error/error_code.h>
+#include <__system_error/error_condition.h>
+#include <__system_error/system_error.h>
 #include <__utility/swap.h>
 #include <__verbose_abort>
-#include <system_error>
 #include <version>
 
 // standard-mandated includes
@@ -1048,6 +1051,7 @@ _LIBCPP_END_NAMESPACE_STD
 #  include <limits>
 #  include <new>
 #  include <stdexcept>
+#  include <system_error>
 #  include <type_traits>
 #  include <typeinfo>
 #endif

libcxx/include/libcxx.imp

@@ -41,6 +41,7 @@
   { include: [ "@<__ranges/.*>", "private", "<ranges>", "public" ] },
   { include: [ "@<__string/.*>", "private", "<string>", "public" ] },
   { include: [ "@<__support/.*>", "private", "<support>", "public" ] },
+  { include: [ "@<__system_error/.*>", "private", "<system_error>", "public" ] },
   { include: [ "@<__thread/.*>", "private", "<thread>", "public" ] },
   { include: [ "@<__tuple_dir/.*>", "private", "<tuple>", "public" ] },
   { include: [ "@<__type_traits/.*>", "private", "<type_traits>", "public" ] },

libcxx/include/locale

@@ -203,6 +203,7 @@ template <class charT> class messages_byname;
 #include <__locale>
 #include <__memory/unique_ptr.h>
 #include <__type_traits/make_unsigned.h>
+#include <cerrno>
 #include <cstdio>
 #include <cstdlib>
 #include <ctime>

libcxx/include/module.modulemap.in

@@ -904,6 +904,7 @@ module std [system] {
         private header "__format/format_context.h"
         export optional
         export locale
+        export __locale
       }
       module format_error                    { private header "__format/format_error.h" }
       module format_functions                {
@@ -1433,7 +1434,22 @@ module std [system] {
   }
   module system_error {
     header "system_error"
+    export __errc
     export *
+    module __system_error {
+      module error_category  { private header "__system_error/error_category.h" }
+      module error_code {
+        private header "__system_error/error_code.h"
+        export functional.__functional.hash
+        export functional.__functional.unary_function
+      }
+      module error_condition {
+        private header "__system_error/error_condition.h"
+        export functional.__functional.hash
+        export functional.__functional.unary_function
+      }
+      module system_error { private header "__system_error/system_error.h" }
+    }
   }
   module thread {
     @requires_LIBCXX_ENABLE_THREADS@

libcxx/include/mutex

@@ -719,6 +719,7 @@ _LIBCPP_POP_MACROS
 #  include <initializer_list>
 #  include <new>
 #  include <stdexcept>
+#  include <system_error>
 #  include <type_traits>
 #  include <typeinfo>
 #endif

libcxx/include/ostream

@@ -168,6 +168,7 @@ basic_ostream<wchar_t, traits>& operator<<(basic_ostream<wchar_t, traits>&, cons
 #include <__exception/operations.h>
 #include <__memory/shared_ptr.h>
 #include <__memory/unique_ptr.h>
+#include <__system_error/error_code.h>
 #include <__type_traits/conjunction.h>
 #include <__type_traits/enable_if.h>
 #include <__type_traits/is_base_of.h>

libcxx/include/shared_mutex

@@ -133,9 +133,9 @@ template <class Mutex>
 #include <__mutex/mutex.h>
 #include <__mutex/tag_types.h>
 #include <__mutex/unique_lock.h>
+#include <__system_error/system_error.h>
 #include <__utility/swap.h>
 #include <cerrno>
-#include <system_error>
 #include <version>
 
 _LIBCPP_PUSH_MACROS
@@ -515,4 +515,8 @@ _LIBCPP_END_NAMESPACE_STD
 
 _LIBCPP_POP_MACROS
 
+#if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
+#  include <system_error>
+#endif
+
 #endif // _LIBCPP_SHARED_MUTEX

libcxx/include/system_error

@@ -146,12 +146,10 @@ template <> struct hash<std::error_condition>;
 
 #include <__assert> // all public C++ headers provide the assertion handler
 #include <__config>
-#include <__errc>
-#include <__functional/hash.h>
-#include <__functional/unary_function.h>
-#include <__memory/addressof.h>
-#include <stdexcept>
-#include <string>
+#include <__system_error/error_category.h>
+#include <__system_error/error_code.h>
+#include <__system_error/error_condition.h>
+#include <__system_error/system_error.h>
 #include <version>
 
 // standard-mandated includes
@@ -163,388 +161,10 @@ template <> struct hash<std::error_condition>;
 #  pragma GCC system_header
 #endif
 
-_LIBCPP_BEGIN_NAMESPACE_STD
-
-// is_error_code_enum
-
-template <class _Tp>
-struct _LIBCPP_TEMPLATE_VIS is_error_code_enum
-    : public false_type {};
-
-#if _LIBCPP_STD_VER >= 17
-template <class _Tp>
-inline constexpr bool is_error_code_enum_v = is_error_code_enum<_Tp>::value;
-#endif
-
-// is_error_condition_enum
-
-template <class _Tp>
-struct _LIBCPP_TEMPLATE_VIS is_error_condition_enum
-    : public false_type {};
-
-#if _LIBCPP_STD_VER >= 17
-template <class _Tp>
-inline constexpr bool is_error_condition_enum_v = is_error_condition_enum<_Tp>::value;
-#endif
-
-template <>
-struct _LIBCPP_TEMPLATE_VIS is_error_condition_enum<errc>
-    : true_type { };
-
-#ifdef _LIBCPP_CXX03_LANG
-template <>
-struct _LIBCPP_TEMPLATE_VIS is_error_condition_enum<errc::__lx>
-    : true_type { };
-#endif
-
-class _LIBCPP_TYPE_VIS error_condition;
-class _LIBCPP_TYPE_VIS error_code;
-
-// class error_category
-
-class _LIBCPP_HIDDEN __do_message;
-
-class _LIBCPP_TYPE_VIS error_category
-{
-public:
-    virtual ~error_category() _NOEXCEPT;
-
-#if defined(_LIBCPP_ERROR_CATEGORY_DEFINE_LEGACY_INLINE_FUNCTIONS)
-    error_category() noexcept;
-#else
-    _LIBCPP_INLINE_VISIBILITY
-    _LIBCPP_CONSTEXPR_SINCE_CXX14 error_category() _NOEXCEPT = default;
-#endif
-    error_category(const error_category&) = delete;
-    error_category& operator=(const error_category&) = delete;
-
-    virtual const char* name() const _NOEXCEPT = 0;
-    virtual error_condition default_error_condition(int __ev) const _NOEXCEPT;
-    virtual bool equivalent(int __code, const error_condition& __condition) const _NOEXCEPT;
-    virtual bool equivalent(const error_code& __code, int __condition) const _NOEXCEPT;
-    virtual string message(int __ev) const = 0;
-
-    _LIBCPP_INLINE_VISIBILITY
-    bool operator==(const error_category& __rhs) const _NOEXCEPT {return this == &__rhs;}
-
-#if _LIBCPP_STD_VER >= 20
-
-    _LIBCPP_HIDE_FROM_ABI
-    strong_ordering operator<=>(const error_category& __rhs) const noexcept {return compare_three_way()(this, std::addressof(__rhs));}
-
-#else // _LIBCPP_STD_VER >= 20
-
-    _LIBCPP_INLINE_VISIBILITY
-    bool operator!=(const error_category& __rhs) const _NOEXCEPT {return !(*this == __rhs);}
-
-    _LIBCPP_INLINE_VISIBILITY
-    bool operator< (const error_category& __rhs) const _NOEXCEPT {return this < &__rhs;}
-
-#endif // _LIBCPP_STD_VER >= 20
-
-    friend class _LIBCPP_HIDDEN __do_message;
-};
-
-class _LIBCPP_HIDDEN __do_message
-    : public error_category
-{
-public:
-    string message(int __ev) const override;
-};
-
-_LIBCPP_FUNC_VIS const error_category& generic_category() _NOEXCEPT;
-_LIBCPP_FUNC_VIS const error_category& system_category() _NOEXCEPT;
-
-namespace __adl_only {
-    // Those cause ADL to trigger but they are not viable candidates,
-    // so they are never actually selected.
-    void make_error_condition() = delete;
-    void make_error_code() = delete;
-} // namespace __adl_only
-
-class _LIBCPP_TYPE_VIS error_condition
-{
-    int __val_;
-    const error_category* __cat_;
-public:
-    _LIBCPP_INLINE_VISIBILITY
-    error_condition() _NOEXCEPT : __val_(0), __cat_(&generic_category()) {}
-
-    _LIBCPP_INLINE_VISIBILITY
-    error_condition(int __val, const error_category& __cat) _NOEXCEPT
-        : __val_(__val), __cat_(&__cat) {}
-
-    template <class _Ep>
-        _LIBCPP_INLINE_VISIBILITY
-        error_condition(_Ep __e,
-              typename enable_if<is_error_condition_enum<_Ep>::value>::type* = nullptr
-                                                                     ) _NOEXCEPT
-            {
-                using __adl_only::make_error_condition;
-                *this = make_error_condition(__e);
-            }
-
-    _LIBCPP_INLINE_VISIBILITY
-    void assign(int __val, const error_category& __cat) _NOEXCEPT
-    {
-        __val_ = __val;
-        __cat_ = &__cat;
-    }
-
-    template <class _Ep>
-        _LIBCPP_INLINE_VISIBILITY
-        typename enable_if
-        <
-            is_error_condition_enum<_Ep>::value,
-            error_condition&
-        >::type
-        operator=(_Ep __e) _NOEXCEPT
-            {
-                using __adl_only::make_error_condition;
-                *this = make_error_condition(__e);
-                return *this;
-            }
-
-    _LIBCPP_INLINE_VISIBILITY
-    void clear() _NOEXCEPT
-    {
-        __val_ = 0;
-        __cat_ = &generic_category();
-    }
-
-    _LIBCPP_INLINE_VISIBILITY
-    int value() const _NOEXCEPT {return __val_;}
-
-    _LIBCPP_INLINE_VISIBILITY
-    const error_category& category() const _NOEXCEPT {return *__cat_;}
-    string message() const;
-
-    _LIBCPP_INLINE_VISIBILITY
-    explicit operator bool() const _NOEXCEPT {return __val_ != 0;}
-};
-
-inline _LIBCPP_INLINE_VISIBILITY
-error_condition
-make_error_condition(errc __e) _NOEXCEPT
-{
-    return error_condition(static_cast<int>(__e), generic_category());
-}
-
-// error_code
-
-class _LIBCPP_TYPE_VIS error_code
-{
-    int __val_;
-    const error_category* __cat_;
-public:
-    _LIBCPP_INLINE_VISIBILITY
-    error_code() _NOEXCEPT : __val_(0), __cat_(&system_category()) {}
-
-    _LIBCPP_INLINE_VISIBILITY
-    error_code(int __val, const error_category& __cat) _NOEXCEPT
-        : __val_(__val), __cat_(&__cat) {}
-
-    template <class _Ep>
-        _LIBCPP_INLINE_VISIBILITY
-        error_code(_Ep __e,
-                   typename enable_if<is_error_code_enum<_Ep>::value>::type* = nullptr
-                                                                     ) _NOEXCEPT
-            {
-                using __adl_only::make_error_code;
-                *this = make_error_code(__e);
-            }
-
-    _LIBCPP_INLINE_VISIBILITY
-    void assign(int __val, const error_category& __cat) _NOEXCEPT
-    {
-        __val_ = __val;
-        __cat_ = &__cat;
-    }
-
-    template <class _Ep>
-        _LIBCPP_INLINE_VISIBILITY
-        typename enable_if
-        <
-            is_error_code_enum<_Ep>::value,
-            error_code&
-        >::type
-        operator=(_Ep __e) _NOEXCEPT
-            {
-                using __adl_only::make_error_code;
-                *this = make_error_code(__e);
-                return *this;
-            }
-
-    _LIBCPP_INLINE_VISIBILITY
-    void clear() _NOEXCEPT
-    {
-        __val_ = 0;
-        __cat_ = &system_category();
-    }
-
-    _LIBCPP_INLINE_VISIBILITY
-    int value() const _NOEXCEPT {return __val_;}
-
-    _LIBCPP_INLINE_VISIBILITY
-    const error_category& category() const _NOEXCEPT {return *__cat_;}
-
-    _LIBCPP_INLINE_VISIBILITY
-    error_condition default_error_condition() const _NOEXCEPT
-        {return __cat_->default_error_condition(__val_);}
-
-    string message() const;
-
-    _LIBCPP_INLINE_VISIBILITY
-    explicit operator bool() const _NOEXCEPT {return __val_ != 0;}
-};
-
-inline _LIBCPP_INLINE_VISIBILITY
-error_code
-make_error_code(errc __e) _NOEXCEPT
-{
-    return error_code(static_cast<int>(__e), generic_category());
-}
-
-inline _LIBCPP_INLINE_VISIBILITY
-bool
-operator==(const error_code& __x, const error_code& __y) _NOEXCEPT
-{
-    return __x.category() == __y.category() && __x.value() == __y.value();
-}
-
-inline _LIBCPP_INLINE_VISIBILITY
-bool
-operator==(const error_code& __x, const error_condition& __y) _NOEXCEPT
-{
-    return __x.category().equivalent(__x.value(), __y)
-        || __y.category().equivalent(__x, __y.value());
-}
-
-#if _LIBCPP_STD_VER <= 17
-inline _LIBCPP_INLINE_VISIBILITY
-bool
-operator==(const error_condition& __x, const error_code& __y) _NOEXCEPT
-{
-    return __y == __x;
-}
-#endif
-
-inline _LIBCPP_INLINE_VISIBILITY
-bool
-operator==(const error_condition& __x, const error_condition& __y) _NOEXCEPT
-{
-    return __x.category() == __y.category() && __x.value() == __y.value();
-}
-
-#if _LIBCPP_STD_VER <= 17
-
-inline _LIBCPP_INLINE_VISIBILITY
-bool
-operator!=(const error_code& __x, const error_code& __y) _NOEXCEPT
-{return !(__x == __y);}
-
-inline _LIBCPP_INLINE_VISIBILITY
-bool
-operator!=(const error_code& __x, const error_condition& __y) _NOEXCEPT
-{return !(__x == __y);}
-
-inline _LIBCPP_INLINE_VISIBILITY
-bool
-operator!=(const error_condition& __x, const error_code& __y) _NOEXCEPT
-{return !(__x == __y);}
-
-inline _LIBCPP_INLINE_VISIBILITY
-bool
-operator!=(const error_condition& __x, const error_condition& __y) _NOEXCEPT
-{return !(__x == __y);}
-
-inline _LIBCPP_INLINE_VISIBILITY
-bool
-operator<(const error_condition& __x, const error_condition& __y) _NOEXCEPT
-{
-    return __x.category() < __y.category()
-        || (__x.category() == __y.category() && __x.value() < __y.value());
-}
-
-inline _LIBCPP_INLINE_VISIBILITY
-bool
-operator<(const error_code& __x, const error_code& __y) _NOEXCEPT
-{
-    return __x.category() < __y.category()
-        || (__x.category() == __y.category() && __x.value() < __y.value());
-}
-
-#else // _LIBCPP_STD_VER <= 17
-
-inline _LIBCPP_HIDE_FROM_ABI strong_ordering
-operator<=>(const error_code& __x, const error_code& __y) noexcept
-{
-    if (auto __c = __x.category() <=> __y.category(); __c != 0)
-        return __c;
-    return __x.value() <=> __y.value();
-}
-
-inline _LIBCPP_HIDE_FROM_ABI strong_ordering
-operator<=>(const error_condition& __x, const error_condition& __y) noexcept
-{
-    if (auto __c = __x.category() <=> __y.category(); __c != 0)
-       return __c;
-    return __x.value() <=> __y.value();
-}
-
-#endif // _LIBCPP_STD_VER <= 17
-
-template <>
-struct _LIBCPP_TEMPLATE_VIS hash<error_code>
-    : public __unary_function<error_code, size_t>
-{
-    _LIBCPP_INLINE_VISIBILITY
-    size_t operator()(const error_code& __ec) const _NOEXCEPT
-    {
-        return static_cast<size_t>(__ec.value());
-    }
-};
-
-template <>
-struct _LIBCPP_TEMPLATE_VIS hash<error_condition>
-    : public __unary_function<error_condition, size_t>
-{
-    _LIBCPP_INLINE_VISIBILITY
-    size_t operator()(const error_condition& __ec) const _NOEXCEPT
-    {
-        return static_cast<size_t>(__ec.value());
-    }
-};
-
-// system_error
-
-class _LIBCPP_TYPE_VIS system_error
-    : public runtime_error
-{
-    error_code __ec_;
-public:
-    system_error(error_code __ec, const string& __what_arg);
-    system_error(error_code __ec, const char* __what_arg);
-    system_error(error_code __ec);
-    system_error(int __ev, const error_category& __ecat, const string& __what_arg);
-    system_error(int __ev, const error_category& __ecat, const char* __what_arg);
-    system_error(int __ev, const error_category& __ecat);
-    system_error(const system_error&) _NOEXCEPT = default;
-    ~system_error() _NOEXCEPT override;
-
-    _LIBCPP_INLINE_VISIBILITY
-    const error_code& code() const _NOEXCEPT {return __ec_;}
-
-private:
-    static string __init(const error_code&, string);
-};
-
-_LIBCPP_NORETURN _LIBCPP_FUNC_VIS
-void __throw_system_error(int __ev, const char* __what_arg);
-
-_LIBCPP_END_NAMESPACE_STD
-
 #if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
+#  include <cstdint>
+#  include <cstring>
+#  include <limits>
 #  include <type_traits>
 #endif
 

libcxx/include/thread

@@ -100,17 +100,19 @@ void sleep_for(const chrono::duration<Rep, Period>& rel_time);
 #include <__format/formatter_integral.h>
 #include <__format/parser_std_format_spec.h>
 #include <__functional/hash.h>
+#include <__functional/unary_function.h>
 #include <__memory/addressof.h>
 #include <__memory/unique_ptr.h>
 #include <__mutex/mutex.h>
 #include <__mutex/unique_lock.h>
+#include <__system_error/system_error.h>
 #include <__thread/poll_with_backoff.h>
 #include <__thread/timed_backoff_policy.h>
 #include <__threading_support>
 #include <__utility/forward.h>
 #include <cstddef>
+#include <cstdint>
 #include <iosfwd>
-#include <system_error>
 #include <tuple>
 #include <version>
 
@@ -469,10 +471,10 @@ _LIBCPP_POP_MACROS
 #endif
 
 #if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
-#  include <cstdint>
 #  include <cstring>
 #  include <functional>
 #  include <new>
+#  include <system_error>
 #endif
 
 #endif // _LIBCPP_THREAD

libcxx/src/chrono.cpp

@@ -12,9 +12,9 @@
 #define _LARGE_TIME_API
 #endif
 
-#include <cerrno>        // errno
+#include <__system_error/system_error.h>
+#include <cerrno> // errno
 #include <chrono>
-#include <system_error>  // __throw_system_error
 
 #if defined(__MVS__)
 #include <__support/ibm/gettod_zos.h> // gettimeofdayMonotonic

libcxx/src/condition_variable.cpp

@@ -12,7 +12,6 @@
 
 #include <condition_variable>
 #include <thread>
-#include <system_error>
 
 #if defined(__ELF__) && defined(_LIBCPP_LINK_PTHREAD_LIB)
 #  pragma comment(lib, "pthread")

libcxx/src/filesystem/filesystem_common.h

@@ -18,8 +18,8 @@
 #include <ctime>
 #include <filesystem>
 #include <ratio>
-#include <system_error>
 #include <utility>
+#include <system_error>
 
 #if defined(_LIBCPP_WIN32API)
 # define WIN32_LEAN_AND_MEAN

libcxx/src/mutex.cpp

@@ -9,7 +9,6 @@
 #include <__assert>
 #include <limits>
 #include <mutex>
-#include <system_error>
 
 #include "include/atomic_support.h"
 

libcxx/src/random.cpp

@@ -13,9 +13,9 @@
 #   define _CRT_RAND_S
 #endif // defined(_LIBCPP_USING_WIN32_RANDOM)
 
+#include <__system_error/system_error.h>
 #include <limits>
 #include <random>
-#include <system_error>
 
 #if defined(__sun__)
 #   define rename solaris_headers_are_broken

libcxx/src/ryu/d2fixed.cpp

@@ -43,7 +43,6 @@
 #include <__config>
 #include <charconv>
 #include <cstring>
-#include <system_error>
 
 #include "include/ryu/common.h"
 #include "include/ryu/d2fixed.h"

libcxx/src/stdexcept.cpp

@@ -9,7 +9,6 @@
 #include <new>
 #include <stdexcept>
 #include <string>
-#include <system_error>
 
 #ifdef _LIBCPP_ABI_VCRUNTIME
 #include "support/runtime/stdexcept_vcruntime.ipp"

libcxx/test/libcxx/private_headers.verify.cpp

@@ -604,6 +604,10 @@ END-SCRIPT
 #include <__string/char_traits.h> // expected-error@*:* {{use of private header from outside its module: '__string/char_traits.h'}}
 #include <__string/constexpr_c_functions.h> // expected-error@*:* {{use of private header from outside its module: '__string/constexpr_c_functions.h'}}
 #include <__string/extern_template_lists.h> // expected-error@*:* {{use of private header from outside its module: '__string/extern_template_lists.h'}}
+#include <__system_error/error_category.h> // expected-error@*:* {{use of private header from outside its module: '__system_error/error_category.h'}}
+#include <__system_error/error_code.h> // expected-error@*:* {{use of private header from outside its module: '__system_error/error_code.h'}}
+#include <__system_error/error_condition.h> // expected-error@*:* {{use of private header from outside its module: '__system_error/error_condition.h'}}
+#include <__system_error/system_error.h> // expected-error@*:* {{use of private header from outside its module: '__system_error/system_error.h'}}
 #include <__thread/poll_with_backoff.h> // expected-error@*:* {{use of private header from outside its module: '__thread/poll_with_backoff.h'}}
 #include <__thread/timed_backoff_policy.h> // expected-error@*:* {{use of private header from outside its module: '__thread/timed_backoff_policy.h'}}
 #include <__tuple_dir/apply_cv.h> // expected-error@*:* {{use of private header from outside its module: '__tuple_dir/apply_cv.h'}}

libcxx/test/libcxx/transitive_includes/cxx03.csv

@@ -158,6 +158,7 @@ concepts cstddef
 concepts type_traits
 concepts version
 condition_variable atomic
+condition_variable cerrno
 condition_variable concepts
 condition_variable cstddef
 condition_variable cstdint
@@ -170,6 +171,7 @@ condition_variable limits
 condition_variable new
 condition_variable ratio
 condition_variable stdexcept
+condition_variable string
 condition_variable system_error
 condition_variable type_traits
 condition_variable typeinfo
@@ -394,6 +396,7 @@ functional utility
 functional vector
 functional version
 future atomic
+future cerrno
 future chrono
 future cstddef
 future cstdint
@@ -407,6 +410,7 @@ future mutex
 future new
 future ratio
 future stdexcept
+future string
 future system_error
 future thread
 future type_traits
@@ -492,6 +496,7 @@ list typeinfo
 list version
 locale atomic
 locale cctype
+locale cerrno
 locale concepts
 locale cstdarg
 locale cstddef
@@ -555,6 +560,7 @@ memory_resource stdexcept
 memory_resource tuple
 memory_resource version
 mutex atomic
+mutex cerrno
 mutex concepts
 mutex cstddef
 mutex cstdint
@@ -568,6 +574,7 @@ mutex limits
 mutex new
 mutex ratio
 mutex stdexcept
+mutex string
 mutex system_error
 mutex type_traits
 mutex typeinfo
@@ -611,6 +618,7 @@ optional variant
 optional version
 ostream atomic
 ostream bitset
+ostream cerrno
 ostream concepts
 ostream cstddef
 ostream cstdint
@@ -625,6 +633,7 @@ ostream locale
 ostream new
 ostream stdexcept
 ostream streambuf
+ostream string
 ostream type_traits
 ostream typeinfo
 ostream version
@@ -739,6 +748,8 @@ shared_mutex ctime
 shared_mutex iosfwd
 shared_mutex limits
 shared_mutex ratio
+shared_mutex stdexcept
+shared_mutex string
 shared_mutex system_error
 shared_mutex type_traits
 shared_mutex version
@@ -829,6 +840,7 @@ system_error string
 system_error type_traits
 system_error version
 thread array
+thread cerrno
 thread chrono
 thread compare
 thread cstddef
@@ -841,6 +853,7 @@ thread limits
 thread locale
 thread new
 thread ratio
+thread stdexcept
 thread string
 thread string_view
 thread system_error

libcxx/test/libcxx/transitive_includes/cxx11.csv

@@ -158,6 +158,7 @@ concepts cstddef
 concepts type_traits
 concepts version
 condition_variable atomic
+condition_variable cerrno
 condition_variable concepts
 condition_variable cstddef
 condition_variable cstdint
@@ -170,6 +171,7 @@ condition_variable limits
 condition_variable new
 condition_variable ratio
 condition_variable stdexcept
+condition_variable string
 condition_variable system_error
 condition_variable type_traits
 condition_variable typeinfo
@@ -394,6 +396,7 @@ functional utility
 functional vector
 functional version
 future atomic
+future cerrno
 future chrono
 future cstddef
 future cstdint
@@ -407,6 +410,7 @@ future mutex
 future new
 future ratio
 future stdexcept
+future string
 future system_error
 future thread
 future type_traits
@@ -492,6 +496,7 @@ list typeinfo
 list version
 locale atomic
 locale cctype
+locale cerrno
 locale concepts
 locale cstdarg
 locale cstddef
@@ -555,6 +560,7 @@ memory_resource stdexcept
 memory_resource tuple
 memory_resource version
 mutex atomic
+mutex cerrno
 mutex concepts
 mutex cstddef
 mutex cstdint
@@ -568,6 +574,7 @@ mutex limits
 mutex new
 mutex ratio
 mutex stdexcept
+mutex string
 mutex system_error
 mutex tuple
 mutex type_traits
@@ -612,6 +619,7 @@ optional variant
 optional version
 ostream atomic
 ostream bitset
+ostream cerrno
 ostream concepts
 ostream cstddef
 ostream cstdint
@@ -626,6 +634,7 @@ ostream locale
 ostream new
 ostream stdexcept
 ostream streambuf
+ostream string
 ostream type_traits
 ostream typeinfo
 ostream version
@@ -740,6 +749,8 @@ shared_mutex ctime
 shared_mutex iosfwd
 shared_mutex limits
 shared_mutex ratio
+shared_mutex stdexcept
+shared_mutex string
 shared_mutex system_error
 shared_mutex type_traits
 shared_mutex version
@@ -830,6 +841,7 @@ system_error string
 system_error type_traits
 system_error version
 thread array
+thread cerrno
 thread chrono
 thread compare
 thread cstddef
@@ -842,6 +854,7 @@ thread limits
 thread locale
 thread new
 thread ratio
+thread stdexcept
 thread string
 thread string_view
 thread system_error

libcxx/test/libcxx/transitive_includes/cxx14.csv

@@ -158,6 +158,7 @@ concepts cstddef
 concepts type_traits
 concepts version
 condition_variable atomic
+condition_variable cerrno
 condition_variable concepts
 condition_variable cstddef
 condition_variable cstdint
@@ -170,6 +171,7 @@ condition_variable limits
 condition_variable new
 condition_variable ratio
 condition_variable stdexcept
+condition_variable string
 condition_variable system_error
 condition_variable type_traits
 condition_variable typeinfo
@@ -396,6 +398,7 @@ functional utility
 functional vector
 functional version
 future atomic
+future cerrno
 future chrono
 future cstddef
 future cstdint
@@ -409,6 +412,7 @@ future mutex
 future new
 future ratio
 future stdexcept
+future string
 future system_error
 future thread
 future type_traits
@@ -494,6 +498,7 @@ list typeinfo
 list version
 locale atomic
 locale cctype
+locale cerrno
 locale concepts
 locale cstdarg
 locale cstddef
@@ -557,6 +562,7 @@ memory_resource stdexcept
 memory_resource tuple
 memory_resource version
 mutex atomic
+mutex cerrno
 mutex concepts
 mutex cstddef
 mutex cstdint
@@ -570,6 +576,7 @@ mutex limits
 mutex new
 mutex ratio
 mutex stdexcept
+mutex string
 mutex system_error
 mutex tuple
 mutex type_traits
@@ -614,6 +621,7 @@ optional variant
 optional version
 ostream atomic
 ostream bitset
+ostream cerrno
 ostream concepts
 ostream cstddef
 ostream cstdint
@@ -628,6 +636,7 @@ ostream locale
 ostream new
 ostream stdexcept
 ostream streambuf
+ostream string
 ostream type_traits
 ostream typeinfo
 ostream version
@@ -742,6 +751,8 @@ shared_mutex ctime
 shared_mutex iosfwd
 shared_mutex limits
 shared_mutex ratio
+shared_mutex stdexcept
+shared_mutex string
 shared_mutex system_error
 shared_mutex type_traits
 shared_mutex version
@@ -832,6 +843,7 @@ system_error string
 system_error type_traits
 system_error version
 thread array
+thread cerrno
 thread chrono
 thread compare
 thread cstddef
@@ -844,6 +856,7 @@ thread limits
 thread locale
 thread new
 thread ratio
+thread stdexcept
 thread string
 thread string_view
 thread system_error

libcxx/test/libcxx/transitive_includes/cxx17.csv

@@ -158,6 +158,7 @@ concepts cstddef
 concepts type_traits
 concepts version
 condition_variable atomic
+condition_variable cerrno
 condition_variable concepts
 condition_variable cstddef
 condition_variable cstdint
@@ -170,6 +171,7 @@ condition_variable limits
 condition_variable new
 condition_variable ratio
 condition_variable stdexcept
+condition_variable string
 condition_variable system_error
 condition_variable type_traits
 condition_variable typeinfo
@@ -396,6 +398,7 @@ functional utility
 functional vector
 functional version
 future atomic
+future cerrno
 future chrono
 future cstddef
 future cstdint
@@ -409,6 +412,7 @@ future mutex
 future new
 future ratio
 future stdexcept
+future string
 future system_error
 future thread
 future type_traits
@@ -494,6 +498,7 @@ list typeinfo
 list version
 locale atomic
 locale cctype
+locale cerrno
 locale concepts
 locale cstdarg
 locale cstddef
@@ -557,6 +562,7 @@ memory_resource stdexcept
 memory_resource tuple
 memory_resource version
 mutex atomic
+mutex cerrno
 mutex concepts
 mutex cstddef
 mutex cstdint
@@ -570,6 +576,7 @@ mutex limits
 mutex new
 mutex ratio
 mutex stdexcept
+mutex string
 mutex system_error
 mutex tuple
 mutex type_traits
@@ -614,6 +621,7 @@ optional variant
 optional version
 ostream atomic
 ostream bitset
+ostream cerrno
 ostream concepts
 ostream cstddef
 ostream cstdint
@@ -628,6 +636,7 @@ ostream locale
 ostream new
 ostream stdexcept
 ostream streambuf
+ostream string
 ostream type_traits
 ostream typeinfo
 ostream version
@@ -742,6 +751,8 @@ shared_mutex ctime
 shared_mutex iosfwd
 shared_mutex limits
 shared_mutex ratio
+shared_mutex stdexcept
+shared_mutex string
 shared_mutex system_error
 shared_mutex type_traits
 shared_mutex version
@@ -832,6 +843,7 @@ system_error string
 system_error type_traits
 system_error version
 thread array
+thread cerrno
 thread chrono
 thread compare
 thread cstddef
@@ -844,6 +856,7 @@ thread limits
 thread locale
 thread new
 thread ratio
+thread stdexcept
 thread string
 thread string_view
 thread system_error

libcxx/test/libcxx/transitive_includes/cxx20.csv

@@ -165,6 +165,7 @@ concepts cstddef
 concepts type_traits
 concepts version
 condition_variable atomic
+condition_variable cerrno
 condition_variable concepts
 condition_variable cstddef
 condition_variable cstdint
@@ -177,6 +178,7 @@ condition_variable limits
 condition_variable new
 condition_variable ratio
 condition_variable stdexcept
+condition_variable string
 condition_variable system_error
 condition_variable type_traits
 condition_variable typeinfo
@@ -403,6 +405,7 @@ functional utility
 functional vector
 functional version
 future atomic
+future cerrno
 future cstddef
 future cstdint
 future cstdlib
@@ -415,6 +418,7 @@ future mutex
 future new
 future ratio
 future stdexcept
+future string
 future system_error
 future thread
 future type_traits
@@ -500,6 +504,7 @@ list typeinfo
 list version
 locale atomic
 locale cctype
+locale cerrno
 locale concepts
 locale cstdarg
 locale cstddef
@@ -563,6 +568,7 @@ memory_resource stdexcept
 memory_resource tuple
 memory_resource version
 mutex atomic
+mutex cerrno
 mutex concepts
 mutex cstddef
 mutex cstdint
@@ -576,6 +582,7 @@ mutex limits
 mutex new
 mutex ratio
 mutex stdexcept
+mutex string
 mutex system_error
 mutex tuple
 mutex type_traits
@@ -620,6 +627,7 @@ optional variant
 optional version
 ostream atomic
 ostream bitset
+ostream cerrno
 ostream concepts
 ostream cstddef
 ostream cstdint
@@ -634,6 +642,7 @@ ostream locale
 ostream new
 ostream stdexcept
 ostream streambuf
+ostream string
 ostream type_traits
 ostream typeinfo
 ostream version
@@ -748,6 +757,8 @@ shared_mutex ctime
 shared_mutex iosfwd
 shared_mutex limits
 shared_mutex ratio
+shared_mutex stdexcept
+shared_mutex string
 shared_mutex system_error
 shared_mutex type_traits
 shared_mutex version
@@ -838,6 +849,7 @@ system_error string
 system_error type_traits
 system_error version
 thread array
+thread cerrno
 thread compare
 thread cstddef
 thread cstdint

libcxx/test/libcxx/transitive_includes/cxx2b.csv

@@ -103,6 +103,7 @@ complex stdexcept
 complex version
 concepts cstddef
 concepts version
+condition_variable cerrno
 condition_variable cstddef
 condition_variable ctime
 condition_variable iosfwd
@@ -110,7 +111,7 @@ condition_variable limits
 condition_variable new
 condition_variable ratio
 condition_variable stdexcept
-condition_variable system_error
+condition_variable string
 condition_variable typeinfo
 condition_variable version
 coroutine compare
@@ -213,7 +214,6 @@ filesystem new
 filesystem ratio
 filesystem string
 filesystem string_view
-filesystem system_error
 filesystem version
 format array
 format cmath
@@ -271,6 +271,7 @@ functional typeinfo
 functional unordered_map
 functional vector
 functional version
+future cerrno
 future cstddef
 future cstdint
 future cstdlib
@@ -282,7 +283,7 @@ future mutex
 future new
 future ratio
 future stdexcept
-future system_error
+future string
 future thread
 future typeinfo
 future version
@@ -297,7 +298,6 @@ ios cstring
 ios iosfwd
 ios mutex
 ios string
-ios system_error
 ios version
 iosfwd version
 iostream ios
@@ -337,6 +337,7 @@ list stdexcept
 list tuple
 list version
 locale cctype
+locale cerrno
 locale cstddef
 locale cstdint
 locale cstdio
@@ -381,6 +382,7 @@ memory_resource new
 memory_resource stdexcept
 memory_resource tuple
 memory_resource version
+mutex cerrno
 mutex cstddef
 mutex cstdint
 mutex ctime
@@ -389,7 +391,7 @@ mutex limits
 mutex new
 mutex ratio
 mutex stdexcept
-mutex system_error
+mutex string
 mutex tuple
 mutex typeinfo
 mutex version
@@ -411,6 +413,7 @@ optional new
 optional stdexcept
 optional version
 ostream bitset
+ostream cerrno
 ostream cstddef
 ostream cstdint
 ostream cstring
@@ -422,6 +425,7 @@ ostream locale
 ostream new
 ostream stdexcept
 ostream streambuf
+ostream string
 ostream typeinfo
 ostream version
 queue compare
@@ -498,7 +502,8 @@ shared_mutex ctime
 shared_mutex iosfwd
 shared_mutex limits
 shared_mutex ratio
-shared_mutex system_error
+shared_mutex stdexcept
+shared_mutex string
 shared_mutex version
 source_location cstdint
 source_location version
@@ -554,13 +559,11 @@ strstream version
 system_error cerrno
 system_error compare
 system_error cstddef
-system_error cstdint
-system_error cstring
-system_error limits
 system_error stdexcept
 system_error string
 system_error version
 thread array
+thread cerrno
 thread compare
 thread cstddef
 thread cstdint
@@ -573,7 +576,6 @@ thread ratio
 thread stdexcept
 thread string
 thread string_view
-thread system_error
 thread tuple
 thread vector
 thread version

libcxx/test/std/diagnostics/syserr/is_error_condition_enum.pass.cpp

@@ -12,6 +12,7 @@
 
 // template <class T> constexpr bool is_error_condition_enum_v;
 
+#include <string>
 #include <system_error>
 #include <type_traits>
 #include "test_macros.h"

libcxx/test/std/diagnostics/syserr/syserr.errcode/syserr.errcode.constructors/ErrorCodeEnum.pass.cpp

@@ -14,6 +14,7 @@
 
 #include <system_error>
 #include <cassert>
+#include <type_traits>
 
 #include "test_macros.h"
 

libcxx/test/std/diagnostics/syserr/syserr.errcode/syserr.errcode.modifiers/ErrorCodeEnum.pass.cpp

@@ -14,6 +14,7 @@
 
 #include <system_error>
 #include <cassert>
+#include <type_traits>
 
 #include "test_macros.h"
 

libcxx/test/std/numerics/rand/rand.device/ctor.pass.cpp

@@ -29,6 +29,7 @@
 // throw.
 
 #include <random>
+#include <string>
 #include <system_error>
 #include <cassert>
 

libcxx/test/std/numerics/rand/rand.device/eval.pass.cpp

@@ -16,6 +16,7 @@
 
 #include <random>
 #include <cassert>
+#include <string>
 #include <system_error>
 
 #include "test_macros.h"

libcxx/test/std/thread/futures/futures.errors/default_error_condition.pass.cpp

@@ -16,6 +16,7 @@
 
 #include <future>
 #include <cassert>
+#include <system_error>
 
 #include "test_macros.h"
 

libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.shared/thread.lock.shared.locking/lock.pass.cpp

@@ -23,6 +23,7 @@
 #include <cstdlib>
 #include <mutex>
 #include <shared_mutex>
+#include <system_error>
 #include <thread>
 #include <vector>
 

libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.shared/thread.lock.shared.locking/unlock.pass.cpp

@@ -17,6 +17,7 @@
 
 #include <shared_mutex>
 #include <cassert>
+#include <cerrno>
 #include <system_error>
 
 #include "test_macros.h"

libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.unique/thread.lock.unique.locking/lock.pass.cpp

@@ -20,6 +20,7 @@
 #include <chrono>
 #include <cstdlib>
 #include <mutex>
+#include <system_error>
 #include <thread>
 
 #include "make_test_thread.h"

libcxx/utils/data/ignore_format.txt

@@ -611,7 +611,10 @@ libcxx/include/__support/newlib/xlocale.h
 libcxx/include/__support/solaris/xlocale.h
 libcxx/include/__support/win32/locale_win32.h
 libcxx/include/__support/xlocale/__nop_locale_mgmt.h
-libcxx/include/system_error
+libcxx/include/__system_error/error_category.h
+libcxx/include/__system_error/error_code.h
+libcxx/include/__system_error/error_condition.h
+libcxx/include/__system_error/system_error.h
 libcxx/include/thread
 libcxx/include/__threading_support
 libcxx/include/__thread/poll_with_backoff.h