Split reference into headers

This reverts commit 8962c9101a.

.travis.yml

@@ -206,7 +206,7 @@ install:
 script:
   - |-
     echo "using $TOOLSET : : $COMPILER ;" > ~/user-config.jam
-  - ./b2 -j3 libs/system/test toolset=$TOOLSET cxxstd=$CXXSTD variant=debug,release ${ADDRMD:+address-model=$ADDRMD} ${UBSAN:+cxxflags=-fsanitize=undefined cxxflags=-fno-sanitize-recover=undefined linkflags=-fsanitize=undefined define=UBSAN=1 debug-symbols=on} ${LINKFLAGS:+linkflags=$LINKFLAGS}
+  - ./b2 -j3 libs/system/test toolset=$TOOLSET cxxstd=$CXXSTD variant=debug,release ${ADDRMD:+address-model=$ADDRMD} ${UBSAN:+undefined-sanitizer=norecover define=UBSAN=1 debug-symbols=on} ${LINKFLAGS:+linkflags=$LINKFLAGS}
 
 notifications:
   email:

doc/system.adoc

@@ -10,7 +10,7 @@ http://www.boost.org/LICENSE_1_0.txt
 # Boost.System: Extensible Error Reporting
 Beman Dawes, Christopher Kohlhoff, Peter Dimov
 :toc: left
-:toclevels: 3
+:toclevels: 4
 :idprefix:
 :docinfo: private-footer
 

doc/system/changes.adoc

@@ -1,5 +1,5 @@
 ////
-Copyright 2018 Peter Dimov
+Copyright 2018-2021 Peter Dimov
 
 Distributed under the Boost Software License, Version 1.0.
 
@@ -11,6 +11,27 @@ http://www.boost.org/LICENSE_1_0.txt
 # Revision History
 :idprefix:
 
+## Changes in Boost 1.77
+
+* The conversion operator from `error_category` to `std::error_category`
+  has been improved and no longer requires `<map>` or `<mutex>`.
+* The comparison operators of `error_category` are now inline friends
+  instead of member functions (a side effect of the previous change.)
+* `error_condition` now defers calling `generic_category()` to avoid
+  instantiating the object until it's actually needed.
+* `error_condition::failed` and `error_condition::message` have been
+  undeprecated, and `operator bool()` now once again returns `failed()`.
+* The system category now doesn't call `generic_category()`, to avoid
+  instantiating the object.
+* The return value of `default_error_condition` changes in some cases into
+  an `error_condition` from the generic category, instead of from the system
+  category. This happens on POSIX when the input `error_code` is from
+  the system category and does not correspond to any `errc_t` value.
+
+## Changes in Boost 1.76
+
+* `windows_error.hpp` is no longer deprecated.
+
 ## Changes in Boost 1.75
 
 * The platform-specific headers `windows_error.hpp`, `linux_error.hpp`,

doc/system/copyright.adoc

@@ -1,5 +1,5 @@
 ////
-Copyright 2018 Peter Dimov
+Copyright 2018-2021 Peter Dimov
 
 Distributed under the Boost Software License, Version 1.0.
 
@@ -14,6 +14,6 @@ http://www.boost.org/LICENSE_1_0.txt
 This documentation is
 
 * Copyright 2003-2017 Beman Dawes
-* Copyright 2018 Peter Dimov
+* Copyright 2018-2021 Peter Dimov
 
 and is distributed under the http://www.boost.org/LICENSE_1_0.txt[Boost Software License, Version 1.0].

doc/system/reference.adoc

@@ -1,6 +1,6 @@
 ////
 Copyright 2003-2017 Beman Dawes
-Copyright 2018 Peter Dimov
+Copyright 2018-2021 Peter Dimov
 
 Distributed under the Boost Software License, Version 1.0.
 
@@ -48,31 +48,53 @@ the old names, but will provide them when the macro `BOOST_SYSTEM_ENABLE_DEPRECA
 |`native_ecat`|`system_category()`
 |===
 
-## <boost/system/error_code.hpp>
+## <boost/system/{zwsp}is_error_code_enum.hpp>
 
-### Synopsis
+### is_error_code_enum
 
 ```
 namespace boost {
   namespace system {
 
-    class error_category;
-
-    constexpr const error_category & system_category() noexcept;
-    constexpr const error_category & generic_category() noexcept;
-
-    class error_code;
-    class error_condition;
-
-    // "Concept" helpers
-
     template<class T>
       struct is_error_code_enum { static const bool value = false; };
 
+  } // namespace system
+} // namespace boost
+```
+
+Users may specialize `is_error_code_enum` for their error enumeration
+types to indicate that they should be eligible for automatic conversions
+to `error_code`. This conversion calls `make_error_code(e)`, which should
+be provided in the same namespace as the enumeration type.
+
+## <boost/system/{zwsp}is_error_condition_enum.hpp>
+
+### is_error_condition_enum
+
+```
+namespace boost {
+  namespace system {
+
     template<class T>
       struct is_error_condition_enum { static const bool value = false; };
 
-    // generic error conditions
+  } // namespace system
+} // namespace boost
+```
+
+Users may specialize `is_error_condition_enum` for their error enumeration
+types to indicate that they should be eligible for automatic conversions
+to `error_condition`. This conversion calls `make_error_condition(e)`, which
+should be provided in the same namespace as the enumeration type.
+
+## <boost/system/{zwsp}errc.hpp>
+
+### errc
+
+```
+namespace boost {
+  namespace system {
 
     namespace errc {
       enum errc_t
@@ -163,52 +185,80 @@ namespace boost {
     template<> struct is_error_condition_enum<errc::errc_t>
       { static const bool value = true; };
 
-    // non-member functions
-
-    constexpr bool operator==( const error_code & lhs,
-      const error_code & rhs ) noexcept;
-    bool operator==( const error_code & code,
-      const error_condition & condition ) noexcept;
-    bool operator==( const error_condition & condition,
-      const error_code & code ) noexcept;
-    constexpr bool operator==( const error_condition & lhs,
-      const error_condition & rhs ) noexcept;
-
-    constexpr bool operator!=( const error_code & lhs,
-      const error_code & rhs ) noexcept;
-    bool operator!=( const error_code & code,
-      const error_condition & condition ) noexcept;
-    bool operator!=( const error_condition & condition,
-      const error_code & code ) noexcept;
-    constexpr bool operator!=( const error_condition & lhs,
-      const error_condition & rhs ) noexcept;
-
-    constexpr bool operator<( const error_code & lhs,
-      const error_code & rhs ) noexcept;
-    constexpr bool operator<( const error_condition & lhs,
-      const error_condition & rhs ) noexcept;
-
     constexpr error_code make_error_code( errc::errc_t e ) noexcept;
     constexpr error_condition make_error_condition( errc::errc_t e ) noexcept;
 
-    template <class charT, class traits>
-      std::basic_ostream<charT, traits>&
-        operator<<( basic_ostream<charT, traits>& os, const error_code & ec );
-
-    std::size_t hash_value( const error_code & ec );
-
   } // namespace system
 } // namespace boost
 ```
 
-The value of each `errc_t` constant is the same as the value of the `<cerrno>`
-macro shown in the above synopsis.
+The predefined enumeration type `errc::errc_t` provides named constants
+corresponding to the values of the `<cerrno>` macros.
 
-Users may specialize `is_error_code_enum` and `is_error_condition_enum`
-templates to indicate that a type is eligible for class `error_code` and
-`error_condition` automatic conversions respectively.
+```
+constexpr error_condition make_error_condition( errc::errc_t e ) noexcept;
+```
+[none]
+* {blank}
++
+Returns: :: `error_condition( e, generic_category() )`.
 
-### Class error_category
+Since `errc::errc_t` provides a specialization of `is_error_condition_enum`
+and an overload of `make_error_condition`, it can be converted implicitly to
+an `error_condition`. This is typically useful when comparing `error_code`
+values returned from APIs to a portable condition, as in the below example:
+* {blank}
++
+```
+void api_function( boost::system::error_code& ec );
+
+void my_function()
+{
+    boost::system::error_code ec;
+    api_function( ec );
+
+    if( ec == boost::system::errc::no_such_file_or_directory )
+    {
+        // an entity wasn't found (ENOENT)
+        // handle this condition
+    }
+}
+```
+
+```
+constexpr error_code make_error_code( errc::errc_t e ) noexcept;
+```
+[none]
+* {blank}
++
+Returns: :: `error_code( e, generic_category() )`.
+
+In addition to `make_error_condition`, `errc::errc_t` provides an overload of
+`make_error_code`. This allows the creation of generic error codes, an
+operation typically useful when a function needs to signal a generic failure
+that does not come from an underlying API, such as for instance an out of
+memory condition:
+* {blank}
++
+```
+void my_api_function( boost::system::error_code& ec )
+{
+    void* p = std::malloc( 16 );
+
+    if( p == 0 )
+    {
+        // return ENOMEM
+        ec = make_error_code( boost::system::errc::out_of_memory );
+        return;
+    }
+
+    // use p
+}
+```
+
+## <boost/system/{zwsp}error_category.hpp>
+
+### error_category
 
 The class `error_category` defines the base class for types used
 to identify the source and encoding of a particular category of error code.
@@ -251,9 +301,13 @@ namespace boost {
 
       virtual bool failed( int ev ) const noexcept;
 
-      constexpr bool operator==( const error_category & rhs ) const noexcept;
-      constexpr bool operator!=( const error_category & rhs ) const noexcept;
-      constexpr bool operator< ( const error_category & rhs ) const noexcept;
+      friend constexpr bool operator==( const error_category & lhs,
+        const error_category & rhs ) noexcept;
+      friend constexpr bool operator!=( const error_category & lhs,
+        const error_category & rhs ) noexcept;
+
+      friend constexpr bool operator< ( const error_category & lhs,
+        const error_category & rhs ) noexcept;
 
       operator std::error_category const & () const;
 
@@ -397,37 +451,42 @@ Returns: ::
 Remarks: ::
   All calls to this function with the same `ev` must return the same value.
 
-#### Nonvirtuals
+#### Comparisons
 
 ```
-constexpr bool operator==( const error_category & rhs ) const noexcept;
+friend constexpr bool operator==( const error_category & lhs,
+  const error_category & rhs ) noexcept;
 ```
 [none]
 * {blank}
 +
-Returns: :: `rhs.id_ == 0? this == &rhs: id_ == rhs.id_`.
-Remarks: :: Two category objects are considered equivalent when they have matching
-  nonzero identifiers, or are the same object.
+Returns: :: `rhs.id_ == 0? &lhs == &rhs: lhs.id_ == rhs.id_`.
+Remarks: :: Two category objects are considered equivalent when they have
+  matching nonzero identifiers, or are the same object.
 
 ```
-constexpr bool operator!=( const error_category & rhs ) const noexcept;
+friend constexpr bool operator!=( const error_category & lhs,
+  const error_category & rhs ) noexcept;
 ```
 [none]
 * {blank}
 +
-Returns: :: `!( *this == rhs )`.
+Returns: :: `!( lhs == rhs )`.
 
 ```
-constexpr bool operator< ( const error_category & rhs ) const noexcept;
+constexpr bool operator< ( const error_category & lhs,
+  const error_category & rhs ) const noexcept;
 ```
 [none]
 * {blank}
 +
 Returns: ::
-** If `id_ < rhs.id_`, `true`;
-** Otherwise, if `id_ > rhs.id_`, `false`;
+** If `lhs.id_ < rhs.id_`, `true`;
+** Otherwise, if `lhs.id_ > rhs.id_`, `false`;
 ** Otherwise, if `rhs.id_ != 0`, `false`;
-** Otherwise, `std::less<error_category const *>()( this, &rhs )`.
+** Otherwise, `std::less<error_category const *>()( &lhs, &rhs )`.
+
+#### Conversions
 
 ```
 operator std::error_category const & () const;
@@ -438,7 +497,19 @@ operator std::error_category const & () const;
 Returns: :: A reference to an `std::error_category` object corresponding
   to `*this`.
 
-### Predefined Categories
+## <boost/system/{zwsp}system_category.hpp>
+
+### system_category
+
+```
+namespace boost {
+  namespace system {
+
+    constexpr const error_category & system_category() noexcept;
+
+  } // namespace system
+} // namespace boost
+```
 
 ```
 constexpr const error_category & system_category() noexcept;
@@ -446,8 +517,22 @@ constexpr const error_category & system_category() noexcept;
 [none]
 * {blank}
 +
-Returns: :: A reference to an `error_category` object identifying errors
-  originating from the operating system.
+Returns: :: A reference to a predefined `error_category` object identifying
+  errors originating from the operating system.
+
+## <boost/system/{zwsp}generic_category.hpp>
+
+### generic_category
+
+```
+namespace boost {
+  namespace system {
+
+    constexpr const error_category & generic_category() noexcept;
+
+  } // namespace system
+} // namespace boost
+```
 
 ```
 constexpr const error_category & generic_category() noexcept;
@@ -455,10 +540,12 @@ constexpr const error_category & generic_category() noexcept;
 [none]
 * {blank}
 +
-Returns: :: A reference to an `error_category` object identifying portable
-  error conditions.
+Returns: :: A reference to a predefined `error_category` object identifying
+  portable error codes and conditions.
 
-### Class error_code
+## <boost/system/{zwsp}error_code.hpp>
+
+### error_code
 
 The class `error_code` describes an object used to hold error code
 values, such as those originating from the operating system or other
@@ -502,14 +589,39 @@ namespace boost {
       constexpr bool failed() const noexcept;
       constexpr explicit operator bool() const noexcept;
 
+      // comparisons:
+
+      friend constexpr bool operator==( const error_code & lhs,
+        const error_code & rhs ) noexcept;
+      friend constexpr bool operator!=( const error_code & lhs,
+        const error_code & rhs ) noexcept;
+
+      friend constexpr bool operator<( const error_code & lhs,
+        const error_code & rhs ) noexcept;
+
+      // conversions:
+
       operator std::error_code() const;
-
-    private: // exposition only
-
-      int val_;
-      const error_category * cat_;
-
     };
+
+    // non-member functions
+
+    bool operator==( const error_code & code,
+      const error_condition & condition ) noexcept;
+    bool operator==( const error_condition & condition,
+      const error_code & code ) noexcept;
+
+    bool operator!=( const error_code & code,
+      const error_condition & condition ) noexcept;
+    bool operator!=( const error_condition & condition,
+      const error_code & code ) noexcept;
+
+    template <class charT, class traits>
+      std::basic_ostream<charT, traits>&
+        operator<<( basic_ostream<charT, traits>& os, const error_code & ec );
+
+    std::size_t hash_value( const error_code & ec );
+
   }
 }
 ```
@@ -522,7 +634,7 @@ constexpr error_code() noexcept;
 [none]
 * {blank}
 +
-Ensures: :: `val_ == 0`; `*cat_ == system_category()`.
+Ensures: :: `value() == 0`; `category() == system_category()`.
 
 ```
 constexpr error_code( int val, const error_category & cat ) noexcept;
@@ -530,7 +642,7 @@ constexpr error_code( int val, const error_category & cat ) noexcept;
 [none]
 * {blank}
 +
-Ensures: :: `val_ == val`; `cat_ == &cat`.
+Ensures: :: `value() == val`; `category() == cat`.
 
 ```
 template <class ErrorCodeEnum>
@@ -550,7 +662,7 @@ constexpr void assign( int val, const error_category & cat ) noexcept;
 [none]
 * {blank}
 +
-Ensures: :: `val_ == val`; `cat_ == &cat`.
+Ensures: :: `value() == val`; `category() == cat`.
 
 ```
 template<typename ErrorCodeEnum>
@@ -569,7 +681,7 @@ constexpr void clear() noexcept;
 * {blank}
 +
 Ensures: ::
-  `val_ == 0`; `*cat_ == system_category()`.
+  `value() == 0`; `category() == system_category()`.
 
 #### Observers
 
@@ -579,7 +691,7 @@ constexpr int value() const noexcept;
 [none]
 * {blank}
 +
-Returns: :: `val_`.
+Returns: :: the error value.
 
 ```
 constexpr const error_category & category() const noexcept;
@@ -587,7 +699,7 @@ constexpr const error_category & category() const noexcept;
 [none]
 * {blank}
 +
-Returns: :: `*cat_`.
+Returns: :: the error category.
 
 ```
 error_condition default_error_condition() const noexcept;
@@ -595,7 +707,7 @@ error_condition default_error_condition() const noexcept;
 [none]
 * {blank}
 +
-Returns: :: `cat_\->default_error_condition( val_ )`.
+Returns: :: `category().default_error_condition( value() )`.
 
 ```
 std::string message() const;
@@ -603,7 +715,7 @@ std::string message() const;
 [none]
 * {blank}
 +
-Returns: :: `cat_\->message( val_ )`.
+Returns: :: `category().message( value() )`.
 
 ```
 char const * message( char * buffer, std::size_t len ) const noexcept;
@@ -611,7 +723,7 @@ char const * message( char * buffer, std::size_t len ) const noexcept;
 [none]
 * {blank}
 +
-Returns: :: `cat_\->message( val_, buffer, len )`.
+Returns: :: `category().message( value(), buffer, len )`.
 
 ```
 constexpr bool failed() const noexcept;
@@ -619,7 +731,7 @@ constexpr bool failed() const noexcept;
 [none]
 * {blank}
 +
-Returns: :: `cat_\->failed( val_ )`.
+Returns: :: `category().failed( value() )`.
 
 ```
 constexpr explicit operator bool() const noexcept;
@@ -627,7 +739,40 @@ constexpr explicit operator bool() const noexcept;
 [none]
 * {blank}
 +
-Returns: :: `failed()`.
+Returns: ::
+  `failed()`.
+
+#### Comparisons
+
+```
+friend constexpr bool operator==( const error_code & lhs,
+  const error_code & rhs ) noexcept;
+```
+[none]
+* {blank}
++
+Returns: :: `lhs.value() == rhs.value() && lhs.category() == rhs.category()`.
+
+```
+friend constexpr bool operator!=( const error_code & lhs,
+  const error_code & rhs ) noexcept;
+```
+[none]
+* {blank}
++
+Returns: :: `!( lhs == rhs )`.
+
+```
+friend constexpr bool operator<( const error_code & lhs,
+  const error_code & rhs ) noexcept;
+```
+[none]
+* {blank}
++
+Returns: ::
+  `lhs.category() < rhs.category() || (lhs.category() == rhs.category() && lhs.value() < rhs.value())`.
+
+#### Conversions
 
 ```
 operator std::error_code() const;
@@ -636,9 +781,55 @@ operator std::error_code() const;
 * {blank}
 +
 Returns: ::
-  `std::error_code( val_, *cat_ )`.
+  `std::error_code( value(), category() )`.
 
-### Class error_condition
+#### Nonmembers
+
+```
+bool operator==( const error_code & code,
+  const error_condition & condition ) noexcept;
+bool operator==( const error_condition & condition,
+  const error_code & code ) noexcept;
+```
+[none]
+* {blank}
++
+Returns: :: `code.category().equivalent(code.value(), condition) || condition.category().equivalent(code, condition.value())`.
+
+```
+bool operator!=( const error_code & code,
+  const error_condition & condition ) noexcept;
+bool operator!=( const error_condition & condition,
+  const error_code & code ) noexcept;
+```
+[none]
+* {blank}
++
+Returns: :: `!( lhs == rhs )`.
+
+```
+template <class charT, class traits>
+  std::basic_ostream<charT, traits>&
+    operator<<( basic_ostream<charT, traits>& os, const error_code & ec );
+```
+[none]
+* {blank}
++
+Effects: :: `os << ec.category().name() << ':' << ec.value()`.
+Returns: :: `os`.
+
+```
+std::size_t hash_value( const error_code & ec );
+```
+[none]
+* {blank}
++
+Returns: ::
+  A hash value representing `ec`.
+
+## <boost/system/{zwsp}error_condition.hpp>
+
+### error_condition
 
 ```
 namespace boost {
@@ -670,21 +861,24 @@ namespace boost {
       constexpr const error_category & category() const noexcept;
 
       std::string message() const;
+      char const * message( char * buffer, std::size_t len ) const noexcept;
 
+      constexpr bool failed() const noexcept;
       constexpr explicit operator bool() const noexcept;
 
+      // comparisons:
+
+      friend constexpr bool operator==( const error_condition & lhs,
+        const error_condition & rhs ) noexcept;
+      friend constexpr bool operator!=( const error_condition & lhs,
+        const error_condition & rhs ) noexcept;
+
+      friend constexpr bool operator<( const error_condition & lhs,
+        const error_condition & rhs ) noexcept;
+
+      // conversions:
+
       operator std::error_condition() const;
-
-      // deprecated members; do not use
-
-      char const * message( char * buffer, std::size_t len ) const noexcept;
-      constexpr bool failed() const noexcept;
-
-    private: // exposition only
-
-      int val_;
-      const error_category * cat_;
-
     };
   }
 }
@@ -698,7 +892,7 @@ constexpr error_condition() noexcept;
 [none]
 * {blank}
 +
-Ensures: :: `val_ == 0`; `*cat_ == generic_category()`.
+Ensures: :: `value() == 0`; `category() == generic_category()`.
 
 ```
 constexpr error_condition( int val, const error_category & cat ) noexcept;
@@ -706,7 +900,7 @@ constexpr error_condition( int val, const error_category & cat ) noexcept;
 [none]
 * {blank}
 +
-Ensures: :: `val_ == val`; `cat_ == &cat`.
+Ensures: :: `value() == val`; `category() == cat`.
 
 ```
 template <class ErrorConditionEnum>
@@ -727,7 +921,7 @@ constexpr void assign( int val, const error_category & cat ) noexcept;
 [none]
 * {blank}
 +
-Ensures: :: `val_ == val`; `cat_ == &cat`.
+Ensures: :: `value() == val`; `category() == cat`.
 
 ```
 template <class ErrorConditionEnum>
@@ -746,7 +940,7 @@ constexpr void clear() noexcept;
 * {blank}
 +
 Ensures: ::
-  `val_ == 0`; `*cat_ == generic_category()`.
+  `value() == 0`; `category() == generic_category()`.
 
 #### Observers
 
@@ -756,7 +950,7 @@ constexpr int value() const noexcept;
 [none]
 * {blank}
 +
-Returns: :: `val_`.
+Returns: :: the error value.
 
 ```
 constexpr const error_category & category() const noexcept;
@@ -764,7 +958,7 @@ constexpr const error_category & category() const noexcept;
 [none]
 * {blank}
 +
-Returns: :: `*cat_`.
+Returns: :: the error category.
 
 ```
 std::string message() const;
@@ -772,26 +966,7 @@ std::string message() const;
 [none]
 * {blank}
 +
-Returns: :: `cat_\->message( val_ )`.
-
-```
-constexpr explicit operator bool() const noexcept;
-```
-[none]
-* {blank}
-+
-Returns: :: `value() != 0`.
-
-```
-operator std::error_condition() const;
-```
-[none]
-* {blank}
-+
-Returns: ::
-  `std::error_condition( val_, *cat_ )`.
-
-#### Deprecated members
+Returns: :: `category().message( value() )`.
 
 ```
 char const * message( char * buffer, std::size_t len ) const noexcept;
@@ -799,12 +974,7 @@ char const * message( char * buffer, std::size_t len ) const noexcept;
 [none]
 * {blank}
 +
-Returns: :: `cat_\->message( val_, buffer, len )`.
-
-WARNING: This member function is deprecated and will be removed. This is done
-      for compatibility with `std::error_condition` as the next release is
-      expected to improve interoperability with `<system_error>` even further.
-      _Note that this does not affect_ `error_code::message`.
+Returns: :: `category().message( value(), buffer, len )`.
 
 ```
 constexpr bool failed() const noexcept;
@@ -812,19 +982,21 @@ constexpr bool failed() const noexcept;
 [none]
 * {blank}
 +
-Returns: :: `cat_\->failed( val_ )`.
-
-WARNING: This member function is deprecated and will be removed. This is done
-      for compatibility with `std::error_condition` as the next release is
-      expected to improve interoperability with `<system_error>` even further.
-      _Note that this does not affect_ `error_code::failed`.
-
-### Nonmember functions
+Returns: :: `category().failed( value() )`.
 
 ```
-constexpr bool operator==( const error_code & lhs,
-  const error_code & rhs ) noexcept;
-constexpr bool operator==( const error_condition & lhs,
+constexpr explicit operator bool() const noexcept;
+```
+[none]
+* {blank}
++
+Returns: ::
+  `failed()`.
+
+#### Comparisons
+
+```
+friend constexpr bool operator==( const error_condition & lhs,
   const error_condition & rhs ) noexcept;
 ```
 [none]
@@ -833,25 +1005,8 @@ constexpr bool operator==( const error_condition & lhs,
 Returns: :: `lhs.value() == rhs.value() && lhs.category() == rhs.category()`.
 
 ```
-bool operator==( const error_code & code,
-  const error_condition & condition ) noexcept;
-bool operator==( const error_condition & condition,
-  const error_code & code ) noexcept;
-```
-[none]
-* {blank}
-+
-Returns: :: `code.category().equivalent( code.value(), condition ) || condition.category().equivalent( code, condition.value() )`.
-
-```
-constexpr bool operator!=( const error_code & lhs,
-  const error_code & rhs ) noexcept;
-constexpr bool operator!=( const error_condition & lhs,
+friend constexpr bool operator!=( const error_condition & lhs,
   const error_condition & rhs ) noexcept;
-bool operator!=( const error_code & code,
-  const error_condition & condition ) noexcept;
-bool operator!=( const error_condition & condition,
-  const error_code & code ) noexcept;
 ```
 [none]
 * {blank}
@@ -859,53 +1014,27 @@ bool operator!=( const error_condition & condition,
 Returns: :: `!( lhs == rhs )`.
 
 ```
-constexpr bool operator<( const error_code & lhs,
-  const error_code & rhs ) noexcept;
-constexpr bool operator<( const error_condition & lhs,
+friend constexpr bool operator<( const error_condition & lhs,
   const error_condition & rhs ) noexcept;
 ```
 [none]
 * {blank}
 +
-Returns: :: `lhs.category() < rhs.category() || ( lhs.category() == rhs.category() && lhs.value() < rhs.value() )`.
+Returns: ::
+  `lhs.category() < rhs.category() || (lhs.category() == rhs.category() && lhs.value() < rhs.value())`.
+
+#### Conversions
 
 ```
-constexpr error_code make_error_code( errc::errc_t e ) noexcept;
-```
-[none]
-* {blank}
-+
-Returns: :: `error_code( e, generic_category() )`.
-
-```
-constexpr error_condition make_error_condition( errc::errc_t e ) noexcept;
-```
-[none]
-* {blank}
-+
-Returns: :: `error_condition( e, generic_category() )`.
-
-```
-template <class charT, class traits>
-  std::basic_ostream<charT, traits>&
-    operator<<( basic_ostream<charT, traits>& os, const error_code & ec );
-```
-[none]
-* {blank}
-+
-Effects: :: `os << ec.category().name() << ':' << ec.value()`.
-Returns: :: `os`.
-
-```
-std::size_t hash_value( const error_code & ec );
+operator std::error_condition() const;
 ```
 [none]
 * {blank}
 +
 Returns: ::
-  A hash value representing `ec`.
+  `std::error_condition( value(), category() )`.
 
-## <boost/system/system_error.hpp>
+## <boost/system/{zwsp}system_error.hpp>
 
 ### Class system_error
 
@@ -982,4 +1111,8 @@ const char * what() const noexcept;
 * {blank}
 +
 Returns: :: A null-terminated character string incorporating the arguments supplied
-  in the constructor, typically of the form `what_arg + ": " + code.message()`.
+  in the constructor, typically of the form `what_arg + ": " + code().message()`.
+
+## <boost/system.hpp>
+
+This convenience header includes all the headers previously described.

include/boost/system/detail/config.hpp

@@ -13,20 +13,10 @@
 
 // BOOST_SYSTEM_HAS_SYSTEM_ERROR
 
-#if !defined(BOOST_NO_CXX11_HDR_SYSTEM_ERROR)
+#if !defined(BOOST_NO_CXX11_HDR_SYSTEM_ERROR) && !defined(BOOST_NO_CXX11_HDR_ATOMIC)
 # define BOOST_SYSTEM_HAS_SYSTEM_ERROR
 #endif
 
-#if BOOST_WORKAROUND(BOOST_GCC, < 40600)
-// g++ 4.4's <map> is not good enough
-# undef BOOST_SYSTEM_HAS_SYSTEM_ERROR
-#endif
-
-#if defined(BOOST_NO_CXX11_HDR_MUTEX)
-// Required for thread-safe map manipulation
-# undef BOOST_SYSTEM_HAS_SYSTEM_ERROR
-#endif
-
 // BOOST_SYSTEM_NOEXCEPT
 // Retained for backward compatibility
 

include/boost/system/detail/error_category.hpp

@@ -19,6 +19,7 @@
 
 #if defined(BOOST_SYSTEM_HAS_SYSTEM_ERROR)
 # include <system_error>
+# include <atomic>
 #endif
 
 namespace boost
@@ -38,11 +39,7 @@ namespace detail
 
 BOOST_SYSTEM_CONSTEXPR bool failed_impl( int ev, error_category const & cat );
 
-#if defined(BOOST_SYSTEM_HAS_SYSTEM_ERROR)
-
-std::error_category const & to_std_category( error_category const & cat );
-
-#endif
+class std_category;
 
 } // namespace detail
 
@@ -58,10 +55,6 @@ private:
     friend std::size_t hash_value( error_code const & ec );
     friend BOOST_SYSTEM_CONSTEXPR bool detail::failed_impl( int ev, error_category const & cat );
 
-#if defined(BOOST_SYSTEM_HAS_SYSTEM_ERROR)
-    friend std::error_category const & detail::to_std_category( error_category const & cat );
-#endif
-
 #if !defined(BOOST_NO_CXX11_DELETED_FUNCTIONS)
 public:
 
@@ -80,6 +73,16 @@ private:
 
     boost::ulong_long_type id_;
 
+#if defined(BOOST_SYSTEM_HAS_SYSTEM_ERROR)
+
+    mutable std::atomic< boost::system::detail::std_category* > ps_;
+
+#else
+
+    boost::system::detail::std_category* ps_;
+
+#endif
+
 protected:
 
 #if !defined(BOOST_NO_CXX11_DEFAULTED_FUNCTIONS) && !defined(BOOST_NO_CXX11_NON_PUBLIC_DEFAULTED_FUNCTIONS)
@@ -97,11 +100,11 @@ protected:
 
 #endif
 
-    BOOST_SYSTEM_CONSTEXPR error_category() BOOST_NOEXCEPT: id_( 0 )
+    BOOST_SYSTEM_CONSTEXPR error_category() BOOST_NOEXCEPT: id_( 0 ), ps_()
     {
     }
 
-    explicit BOOST_SYSTEM_CONSTEXPR error_category( boost::ulong_long_type id ) BOOST_NOEXCEPT: id_( id )
+    explicit BOOST_SYSTEM_CONSTEXPR error_category( boost::ulong_long_type id ) BOOST_NOEXCEPT: id_( id ), ps_()
     {
     }
 
@@ -121,24 +124,24 @@ public:
         return ev != 0;
     }
 
-    BOOST_SYSTEM_CONSTEXPR bool operator==( const error_category & rhs ) const BOOST_NOEXCEPT
+    friend BOOST_SYSTEM_CONSTEXPR bool operator==( error_category const & lhs, error_category const & rhs ) BOOST_NOEXCEPT
     {
-        return rhs.id_ == 0? this == &rhs: id_ == rhs.id_;
+        return rhs.id_ == 0? &lhs == &rhs: lhs.id_ == rhs.id_;
     }
 
-    BOOST_SYSTEM_CONSTEXPR bool operator!=( const error_category & rhs ) const BOOST_NOEXCEPT
+    friend BOOST_SYSTEM_CONSTEXPR bool operator!=( error_category const & lhs, error_category const & rhs ) BOOST_NOEXCEPT
     {
-        return !( *this == rhs );
+        return !( lhs == rhs );
     }
 
-    BOOST_SYSTEM_CONSTEXPR bool operator<( const error_category & rhs ) const BOOST_NOEXCEPT
+    friend BOOST_SYSTEM_CONSTEXPR bool operator<( error_category const & lhs, error_category const & rhs ) BOOST_NOEXCEPT
     {
-        if( id_ < rhs.id_ )
+        if( lhs.id_ < rhs.id_ )
         {
             return true;
         }
 
-        if( id_ > rhs.id_ )
+        if( lhs.id_ > rhs.id_ )
         {
             return false;
         }
@@ -148,13 +151,15 @@ public:
             return false; // equal
         }
 
-        return std::less<error_category const *>()( this, &rhs );
+        return std::less<error_category const *>()( &lhs, &rhs );
     }
 
 #if defined(BOOST_SYSTEM_HAS_SYSTEM_ERROR)
-
+# if defined(__SUNPRO_CC) // trailing __global is not supported
     operator std::error_category const & () const;
-
+# else
+    operator std::error_category const & () const BOOST_SYMBOL_VISIBLE;
+# endif
 #endif
 };
 

include/boost/system/detail/error_category_impl.hpp

@@ -96,11 +96,40 @@ inline char const * error_category::message( int ev, char * buffer, std::size_t
 
 #if defined(BOOST_SYSTEM_HAS_SYSTEM_ERROR)
 
-#include <boost/system/detail/to_std_category.hpp>
+#include <boost/system/detail/std_category.hpp>
 
 inline boost::system::error_category::operator std::error_category const & () const
 {
-    return boost::system::detail::to_std_category( *this );
+    if( id_ == boost::system::detail::system_category_id )
+    {
+        static const boost::system::detail::std_category system_instance( this, 0x1F4D7 );
+        return system_instance;
+    }
+
+    if( id_ == boost::system::detail::generic_category_id )
+    {
+        static const boost::system::detail::std_category generic_instance( this, 0x1F4D3 );
+        return generic_instance;
+    }
+
+    boost::system::detail::std_category* p = ps_.load( std::memory_order_acquire );
+
+    if( p != 0 )
+    {
+        return *p;
+    }
+
+    boost::system::detail::std_category* q = new detail::std_category( this, 0 );
+
+    if( ps_.compare_exchange_strong( p, q, std::memory_order_release, std::memory_order_acquire ) )
+    {
+        return *q;
+    }
+    else
+    {
+        delete q;
+        return *p;
+    }
 }
 
 #endif // #if defined(BOOST_SYSTEM_HAS_SYSTEM_ERROR)

include/boost/system/detail/error_condition.hpp

@@ -13,6 +13,8 @@
 #include <boost/system/detail/error_category.hpp>
 #include <boost/system/detail/generic_category.hpp>
 #include <boost/system/detail/enable_if.hpp>
+#include <boost/system/detail/is_same.hpp>
+#include <boost/system/detail/errc.hpp>
 #include <boost/system/is_error_condition_enum.hpp>
 #include <boost/system/detail/config.hpp>
 #include <boost/config.hpp>
@@ -27,6 +29,17 @@ namespace system
 
 // error_conditions are portable, error_codes are system or library specific
 
+namespace detail
+{
+
+struct generic_value_tag
+{
+    int value;
+    BOOST_SYSTEM_CONSTEXPR explicit generic_value_tag( int v ): value( v ) {}
+};
+
+} // namespace detail
+
 class error_condition
 {
 private:
@@ -39,7 +52,7 @@ public:
     // constructors:
 
     BOOST_SYSTEM_CONSTEXPR error_condition() BOOST_NOEXCEPT:
-        val_( 0 ), cat_( &generic_category() )
+        val_( 0 ), cat_( 0 )
     {
     }
 
@@ -48,12 +61,25 @@ public:
     {
     }
 
+    BOOST_SYSTEM_CONSTEXPR explicit error_condition( boost::system::detail::generic_value_tag vt ) BOOST_NOEXCEPT:
+        val_( vt.value ), cat_( 0 )
+    {
+    }
+
     template<class ErrorConditionEnum> BOOST_SYSTEM_CONSTEXPR error_condition( ErrorConditionEnum e,
-        typename detail::enable_if<is_error_condition_enum<ErrorConditionEnum>::value>::type* = 0) BOOST_NOEXCEPT
+      typename detail::enable_if<
+        is_error_condition_enum<ErrorConditionEnum>::value && !boost::system::detail::is_same<ErrorConditionEnum, errc::errc_t>::value
+      >::type* = 0) BOOST_NOEXCEPT
     {
         *this = make_error_condition( e );
     }
 
+    template<class ErrorConditionEnum> BOOST_SYSTEM_CONSTEXPR error_condition( ErrorConditionEnum e,
+      typename detail::enable_if<boost::system::detail::is_same<ErrorConditionEnum, errc::errc_t>::value>::type* = 0) BOOST_NOEXCEPT:
+        val_( e ), cat_( 0 )
+    {
+    }
+
     // modifiers:
 
     BOOST_SYSTEM_CONSTEXPR void assign( int val, const error_category & cat ) BOOST_NOEXCEPT
@@ -66,14 +92,14 @@ public:
         BOOST_SYSTEM_CONSTEXPR typename detail::enable_if<is_error_condition_enum<ErrorConditionEnum>::value, error_condition>::type &
         operator=( ErrorConditionEnum val ) BOOST_NOEXCEPT
     {
-        *this = make_error_condition( val );
+        *this = error_condition( val );
         return *this;
     }
 
     BOOST_SYSTEM_CONSTEXPR void clear() BOOST_NOEXCEPT
     {
         val_ = 0;
-        cat_ = &generic_category();
+        cat_ = 0;
     }
 
     // observers:
@@ -85,29 +111,50 @@ public:
 
     BOOST_SYSTEM_CONSTEXPR const error_category & category() const BOOST_NOEXCEPT
     {
-        return *cat_;
+        return cat_? *cat_: generic_category();
     }
 
     std::string message() const
     {
-        return cat_->message( value() );
+        if( cat_ )
+        {
+            return cat_->message( value() );
+        }
+        else
+        {
+            return generic_category().message( value() );
+        }
     }
 
-    BOOST_SYSTEM_DEPRECATED("this function is slated for removal") char const * message( char * buffer, std::size_t len ) const BOOST_NOEXCEPT
+    char const * message( char * buffer, std::size_t len ) const BOOST_NOEXCEPT
     {
-        return cat_->message( value(), buffer, len );
+        if( cat_ )
+        {
+            return cat_->message( value(), buffer, len );
+        }
+        else
+        {
+            return generic_category().message( value(), buffer, len );
+        }
     }
 
-    BOOST_SYSTEM_DEPRECATED("this function is slated for removal") BOOST_SYSTEM_CONSTEXPR bool failed() const BOOST_NOEXCEPT
+    BOOST_SYSTEM_CONSTEXPR bool failed() const BOOST_NOEXCEPT
     {
-        return detail::failed_impl( val_, *cat_ );
+        if( cat_ )
+        {
+            return detail::failed_impl( val_, *cat_ );
+        }
+        else
+        {
+            return val_ != 0;
+        }
     }
 
 #if !defined(BOOST_NO_CXX11_EXPLICIT_CONVERSION_OPERATORS)
 
     BOOST_SYSTEM_CONSTEXPR explicit operator bool() const BOOST_NOEXCEPT  // true if error
     {
-        return val_ != 0;
+        return failed();
     }
 
 #else
@@ -117,12 +164,12 @@ public:
 
     BOOST_SYSTEM_CONSTEXPR operator unspecified_bool_type() const BOOST_NOEXCEPT  // true if error
     {
-        return val_ != 0? unspecified_bool_true: 0;
+        return failed()? unspecified_bool_true: 0;
     }
 
     BOOST_SYSTEM_CONSTEXPR bool operator!() const BOOST_NOEXCEPT  // true if no error
     {
-        return val_ == 0;
+        return !failed();
     }
 
 #endif
@@ -133,12 +180,19 @@ public:
 
     BOOST_SYSTEM_CONSTEXPR inline friend bool operator==( const error_condition & lhs, const error_condition & rhs ) BOOST_NOEXCEPT
     {
-        return lhs.val_ == rhs.val_ && *lhs.cat_ == *rhs.cat_;
+        return lhs.val_ == rhs.val_ && lhs.category() == rhs.category();
     }
 
     BOOST_SYSTEM_CONSTEXPR inline friend bool operator<( const error_condition & lhs, const error_condition & rhs ) BOOST_NOEXCEPT
     {
-        return *lhs.cat_ < *rhs.cat_ || ( *lhs.cat_ == *rhs.cat_ && lhs.val_ < rhs.val_ );
+        error_category const& lcat = lhs.category();
+        error_category const& rcat = rhs.category();
+        return lcat < rcat || ( lcat == rcat && lhs.val_ < rhs.val_ );
+    }
+
+    BOOST_SYSTEM_CONSTEXPR inline friend bool operator!=( const error_condition & lhs, const error_condition & rhs ) BOOST_NOEXCEPT
+    {
+        return !( lhs == rhs );
     }
 
 #if defined(BOOST_SYSTEM_HAS_SYSTEM_ERROR)
@@ -151,11 +205,6 @@ public:
 #endif
 };
 
-BOOST_SYSTEM_CONSTEXPR inline bool operator!=( const error_condition & lhs, const error_condition & rhs ) BOOST_NOEXCEPT
-{
-    return !( lhs == rhs );
-}
-
 } // namespace system
 
 } // namespace boost

include/boost/system/detail/is_generic_value.hpp

@@ -1,125 +0,0 @@
-#ifndef BOOST_SYSTEM_DETAIL_IS_GENERIC_VALUE_HPP_INCLUDED
-#define BOOST_SYSTEM_DETAIL_IS_GENERIC_VALUE_HPP_INCLUDED
-
-// Copyright 2018 Peter Dimov
-//
-// Distributed under the Boost Software License, Version 1.0. (See accompanying
-// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
-//
-// See library home page at http://www.boost.org/libs/system
-
-#include <boost/system/detail/errc.hpp>
-
-namespace boost
-{
-
-namespace system
-{
-
-namespace detail
-{
-
-inline bool is_generic_value( int ev ) BOOST_NOEXCEPT
-{
-    using namespace errc;
-
-    static int const gen[] =
-    {
-        success,
-        address_family_not_supported,
-        address_in_use,
-        address_not_available,
-        already_connected,
-        argument_list_too_long,
-        argument_out_of_domain,
-        bad_address,
-        bad_file_descriptor,
-        bad_message,
-        broken_pipe,
-        connection_aborted,
-        connection_already_in_progress,
-        connection_refused,
-        connection_reset,
-        cross_device_link,
-        destination_address_required,
-        device_or_resource_busy,
-        directory_not_empty,
-        executable_format_error,
-        file_exists,
-        file_too_large,
-        filename_too_long,
-        function_not_supported,
-        host_unreachable,
-        identifier_removed,
-        illegal_byte_sequence,
-        inappropriate_io_control_operation,
-        interrupted,
-        invalid_argument,
-        invalid_seek,
-        io_error,
-        is_a_directory,
-        message_size,
-        network_down,
-        network_reset,
-        network_unreachable,
-        no_buffer_space,
-        no_child_process,
-        no_link,
-        no_lock_available,
-        no_message_available,
-        no_message,
-        no_protocol_option,
-        no_space_on_device,
-        no_stream_resources,
-        no_such_device_or_address,
-        no_such_device,
-        no_such_file_or_directory,
-        no_such_process,
-        not_a_directory,
-        not_a_socket,
-        not_a_stream,
-        not_connected,
-        not_enough_memory,
-        not_supported,
-        operation_canceled,
-        operation_in_progress,
-        operation_not_permitted,
-        operation_not_supported,
-        operation_would_block,
-        owner_dead,
-        permission_denied,
-        protocol_error,
-        protocol_not_supported,
-        read_only_file_system,
-        resource_deadlock_would_occur,
-        resource_unavailable_try_again,
-        result_out_of_range,
-        state_not_recoverable,
-        stream_timeout,
-        text_file_busy,
-        timed_out,
-        too_many_files_open_in_system,
-        too_many_files_open,
-        too_many_links,
-        too_many_symbolic_link_levels,
-        value_too_large,
-        wrong_protocol_type
-    };
-
-    int const n = sizeof( gen ) / sizeof( gen[0] );
-
-    for( int i = 0; i < n; ++i )
-    {
-        if( ev == gen[ i ] ) return true;
-    }
-
-    return false;
-}
-
-} // namespace detail
-
-} // namespace system
-
-} // namespace boost
-
-#endif // #ifndef BOOST_SYSTEM_DETAIL_IS_GENERIC_VALUE_HPP_INCLUDED

include/boost/system/detail/is_same.hpp

@@ -0,0 +1,33 @@
+#ifndef BOOST_SYSTEM_DETAIL_IS_SAME_HPP_INCLUDED
+#define BOOST_SYSTEM_DETAIL_IS_SAME_HPP_INCLUDED
+
+// Copyright 2021 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0
+// http://www.boost.org/LICENSE_1_0.txt
+
+namespace boost
+{
+
+namespace system
+{
+
+namespace detail
+{
+
+template<class T1, class T2> struct is_same
+{
+    enum _vt { value = 0 };
+};
+
+template<class T> struct is_same<T, T>
+{
+    enum _vt { value = 1 };
+};
+
+} // namespace detail
+
+} // namespace system
+
+} // namespace boost
+
+#endif // #ifndef BOOST_SYSTEM_DETAIL_IS_SAME_HPP_INCLUDED

include/boost/system/detail/std_category.hpp

@@ -1,9 +1,9 @@
-#ifndef BOOST_SYSTEM_DETAIL_TO_STD_CATEGORY_HPP_INCLUDED
-#define BOOST_SYSTEM_DETAIL_TO_STD_CATEGORY_HPP_INCLUDED
+#ifndef BOOST_SYSTEM_DETAIL_STD_CATEGORY_HPP_INCLUDED
+#define BOOST_SYSTEM_DETAIL_STD_CATEGORY_HPP_INCLUDED
 
 // Support for interoperability between Boost.System and <system_error>
 //
-// Copyright 2018 Peter Dimov
+// Copyright 2018, 2021 Peter Dimov
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
@@ -15,9 +15,6 @@
 #include <boost/system/detail/error_code.hpp>
 #include <boost/system/detail/generic_category.hpp>
 #include <system_error>
-#include <map>
-#include <memory>
-#include <mutex>
 
 //
 
@@ -73,54 +70,6 @@ public:
     bool equivalent( const std::error_code & code, int condition ) const BOOST_NOEXCEPT BOOST_OVERRIDE;
 };
 
-#if !defined(__SUNPRO_CC) // trailing __global is not supported
-inline std::error_category const & to_std_category( boost::system::error_category const & cat ) BOOST_SYMBOL_VISIBLE;
-#endif
-
-struct cat_ptr_less
-{
-    bool operator()( boost::system::error_category const * p1, boost::system::error_category const * p2 ) const BOOST_NOEXCEPT
-    {
-        return *p1 < *p2;
-    }
-};
-
-inline std::error_category const & to_std_category( boost::system::error_category const & cat )
-{
-    if( cat.id_ == boost::system::detail::system_category_id )
-    {
-        static const std_category system_instance( &cat, 0x1F4D7 );
-        return system_instance;
-    }
-    else if( cat.id_ == boost::system::detail::generic_category_id )
-    {
-        static const std_category generic_instance( &cat, 0x1F4D3 );
-        return generic_instance;
-    }
-    else
-    {
-        typedef std::map< boost::system::error_category const *, std::unique_ptr<std_category>, cat_ptr_less > map_type;
-
-        static map_type map_;
-        static std::mutex map_mx_;
-
-        std::lock_guard<std::mutex> guard( map_mx_ );
-
-        map_type::iterator i = map_.find( &cat );
-
-        if( i == map_.end() )
-        {
-            std::unique_ptr<std_category> p( new std_category( &cat, 0 ) );
-
-            std::pair<map_type::iterator, bool> r = map_.insert( map_type::value_type( &cat, std::move( p ) ) );
-
-            i = r.first;
-        }
-
-        return *i->second;
-    }
-}
-
 inline bool std_category::equivalent( int code, const std::error_condition & condition ) const BOOST_NOEXCEPT
 {
     if( condition.category() == *this )
@@ -170,6 +119,7 @@ inline bool std_category::equivalent( const std::error_code & code, int conditio
         boost::system::error_code bc( code.value(), *pc2->pc_ );
         return pc_->equivalent( bc, condition );
     }
+
 #endif
 
     else if( *pc_ == boost::system::generic_category() )
@@ -188,4 +138,4 @@ inline bool std_category::equivalent( const std::error_code & code, int conditio
 
 } // namespace boost
 
-#endif // #ifndef BOOST_SYSTEM_DETAIL_TO_STD_CATEGORY_HPP_INCLUDED
+#endif // #ifndef BOOST_SYSTEM_DETAIL_STD_CATEGORY_HPP_INCLUDED

include/boost/system/detail/system_category_impl.hpp

@@ -12,9 +12,7 @@
 
 #include <boost/system/detail/system_category.hpp>
 #include <boost/system/detail/error_condition.hpp>
-#include <boost/system/detail/generic_category.hpp>
 #include <boost/system/api_config.hpp>
-#include <boost/config.hpp>
 
 #if !defined(BOOST_POSIX_API) && !defined(BOOST_WINDOWS_API)
 #  error BOOST_POSIX_API or BOOST_WINDOWS_API must be defined
@@ -37,7 +35,7 @@ inline boost::system::error_condition boost::system::detail::system_error_catego
     }
     else
     {
-        return error_condition( e2, generic_category() );
+        return error_condition( boost::system::detail::generic_value_tag( e2 ) );
     }
 }
 
@@ -54,18 +52,10 @@ inline char const * boost::system::detail::system_error_category::message( int e
 #else // #if defined(BOOST_WINDOWS_API)
 
 #include <boost/system/detail/generic_category_message.hpp>
-#include <boost/system/detail/is_generic_value.hpp>
 
 inline boost::system::error_condition boost::system::detail::system_error_category::default_error_condition( int ev ) const BOOST_NOEXCEPT
 {
-    if( is_generic_value( ev ) )
-    {
-        return error_condition( ev, generic_category() );
-    }
-    else
-    {
-        return error_condition( ev, *this );
-    }
+    return error_condition( boost::system::detail::generic_value_tag( ev ) );
 }
 
 inline std::string boost::system::detail::system_error_category::message( int ev ) const

test/Jamfile.v2

@@ -56,7 +56,7 @@ system-run generic_category_test.cpp ;
 system-run system_category_test.cpp ;
 system-run after_main_test.cpp ;
 system-run failed_test.cpp ;
-system-run failed_constexpr_test.cpp ;
+compile failed_constexpr_test.cpp : <toolset>gcc,<undefined-sanitizer>norecover:<build>no ;
 
 # Quick (CI) test
 run quick.cpp ;

test/failed_constexpr_test.cpp

@@ -35,16 +35,28 @@ BOOST_STATIC_ASSERT( !ec3 );
 
 constexpr error_condition en1( 1, system_category() );
 
+#if __GNUC__ == 7 && __cplusplus == 201703L
+// `cat_ != 0` is not a constant expression
+#else
+
 BOOST_STATIC_ASSERT( en1.failed() );
 BOOST_STATIC_ASSERT( en1 );
 BOOST_STATIC_ASSERT( !!en1 );
 
+#endif
+
 constexpr error_condition en2( 2, generic_category() );
 
+#if __GNUC__ == 7 && __cplusplus == 201703L
+// `cat_ != 0` is not a constant expression
+#else
+
 BOOST_STATIC_ASSERT( en2.failed() );
 BOOST_STATIC_ASSERT( en2 );
 BOOST_STATIC_ASSERT( !!en2 );
 
+#endif
+
 constexpr error_condition en3;
 
 BOOST_STATIC_ASSERT( !en3.failed() );

test/system_category_test3.cpp

@@ -18,7 +18,9 @@ int main()
 
     // default_error_condition
     BOOST_TEST( cat.default_error_condition( 0 ) == sys::error_condition() );
-    BOOST_TEST( cat.default_error_condition( -1 ) == sys::error_condition( -1, cat ) );
+
+    // No longer holds; returns a generic condition
+    // BOOST_TEST( cat.default_error_condition( -1 ) == sys::error_condition( -1, cat ) );
 
 #if defined(BOOST_WINDOWS_API)