Remove the user-provided ~error_category in C++03 mode, to fix use after main

appveyor.yml

@@ -1,4 +1,4 @@
-# Copyright 2016, 2017 Peter Dimov
+# Copyright 2016-2018 Peter Dimov
 # Distributed under the Boost Software License, Version 1.0.
 # (See accompanying file LICENSE_1_0.txt or copy at http://boost.org/LICENSE_1_0.txt)
 
@@ -15,48 +15,30 @@ branches:
 environment:
   matrix:
     - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2013
-      TOOLSET: msvc-9.0
-    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2013
-      TOOLSET: msvc-10.0
-    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2013
-      TOOLSET: msvc-11.0
-    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2013
-      TOOLSET: msvc-12.0
+      TOOLSET: msvc-9.0,msvc-10.0,msvc-11.0,msvc-12.0
     - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
       TOOLSET: msvc-14.0
+      ADDRMD: 32,64
     - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
       TOOLSET: msvc-14.1
-    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
-      TOOLSET: msvc-14.1
-      CXXSTD: 17
+      CXXSTD: 14,17
+      ADDRMD: 32,64
     - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2013
       ADDPATH: C:\cygwin\bin;
       TOOLSET: gcc
-    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2013
-      ADDPATH: C:\cygwin\bin;
-      TOOLSET: gcc
-      CXXSTD: 03,11
+      CXXSTD: 03,11,14,1z
     - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2013
       ADDPATH: C:\cygwin64\bin;
       TOOLSET: gcc
-    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2013
-      ADDPATH: C:\cygwin64\bin;
-      TOOLSET: gcc
-      CXXSTD: 03,11
+      CXXSTD: 03,11,14,1z
     - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2013
       ADDPATH: C:\mingw\bin;
       TOOLSET: gcc
-    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2013
-      ADDPATH: C:\mingw\bin;
-      TOOLSET: gcc
-      CXXSTD: 03,11
+      CXXSTD: 03,11,14,1z
     - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2013
       ADDPATH: C:\mingw-w64\x86_64-6.3.0-posix-seh-rt_v5-rev1\mingw64\bin;
       TOOLSET: gcc
-    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2013
-      ADDPATH: C:\mingw-w64\x86_64-6.3.0-posix-seh-rt_v5-rev1\mingw64\bin;
-      TOOLSET: gcc
-      CXXSTD: 03,11
+      CXXSTD: 03,11,14,1z
 
 install:
   - set BOOST_BRANCH=develop
@@ -77,4 +59,5 @@ build: off
 test_script:
   - PATH=%ADDPATH%%PATH%
   - if not "%CXXSTD%" == "" set CXXSTD=cxxstd=%CXXSTD%
-  - b2 -j3 libs/system/test toolset=%TOOLSET% variant=debug,release %CXXSTD%
+  - if not "%ADDRMD%" == "" set ADDRMD=address-model=%ADDRMD%
+  - b2 -j3 libs/system/test toolset=%TOOLSET% %CXXSTD% %ADDRMD% variant=debug,release

include/boost/system/detail/generic_category.hpp

@@ -20,45 +20,71 @@ namespace detail
 
 #if defined(__GLIBC__)
 
-// std::strerror is not thread-safe on glibc (for no reason)
-// glibc also has two incompatible strerror_r definitions (for no reason)
+// glibc has two incompatible strerror_r definitions
 
-inline char const * strerror_r_helper( char const * r, char const * )
+inline char const * strerror_r_helper( char const * r, char const * ) BOOST_NOEXCEPT
 {
     return r;
 }
 
-inline char const * strerror_r_helper( int r, char const * buffer )
+inline char const * strerror_r_helper( int r, char const * buffer ) BOOST_NOEXCEPT
 {
     return r == 0? buffer: "Unknown error";
 }
 
+inline char const * generic_error_category_message( int ev, char * buffer, std::size_t len ) BOOST_NOEXCEPT
+{
+    return strerror_r_helper( strerror_r( ev, buffer, len ), buffer );
+}
+
 inline std::string generic_error_category_message( int ev )
 {
     char buffer[ 128 ];
-    return strerror_r_helper( strerror_r( ev, buffer, sizeof( buffer ) ), buffer );
+    return generic_error_category_message( ev, buffer, sizeof( buffer ) );
 }
 
 #else
 
 // std::strerror is thread-safe on everything else, incl. Windows
 
-inline std::string generic_error_category_message( int ev )
-{
 # if defined( BOOST_MSVC )
 #  pragma warning( push )
 #  pragma warning( disable: 4996 )
 # endif
 
+inline std::string generic_error_category_message( int ev )
+{
     char const * m = std::strerror( ev );
+    return m? m: "Unknown error";
+}
+
+inline char const * generic_error_category_message( int ev, char * buffer, std::size_t len ) BOOST_NOEXCEPT
+{
+    if( len == 0 )
+    {
+        return buffer;
+    }
+
+    if( len == 1 )
+    {
+        buffer[0] = 0;
+        return buffer;
+    }
+
+    char const * m = std::strerror( ev );
+
+    if( m == 0 ) return "Unknown error";
+
+    std::strncpy( buffer, m, len - 1 );
+    buffer[ len-1 ] = 0;
+
+    return buffer;
+}
 
 # if defined( BOOST_MSVC )
 #  pragma warning( pop )
 # endif
 
-    return m? m: "Unknown error";
-}
-
 #endif
 
 } // namespace detail

include/boost/system/detail/system_category_win32.hpp

@@ -12,6 +12,8 @@
 #include <boost/winapi/error_codes.hpp>
 #include <boost/winapi/error_handling.hpp>
 #include <boost/winapi/character_code_conversion.hpp>
+#include <boost/winapi/local_memory.hpp>
+#include <cstdio>
 
 //
 
@@ -24,66 +26,167 @@ namespace system
 namespace detail
 {
 
+#if ( defined(_MSC_VER) && _MSC_VER < 1900 ) || ( defined(__MINGW32__) && !defined(__MINGW64_VERSION_MAJOR) )
+
+inline char const * unknown_message_win32( int ev, char * buffer, std::size_t len )
+{
+# if defined( BOOST_MSVC )
+#  pragma warning( push )
+#  pragma warning( disable: 4996 )
+# endif
+
+    _snprintf( buffer, len - 1, "Unknown error (%d)", ev );
+
+    buffer[ len - 1 ] = 0;
+    return buffer;
+
+# if defined( BOOST_MSVC )
+#  pragma warning( pop )
+# endif
+}
+
+#else
+
+inline char const * unknown_message_win32( int ev, char * buffer, std::size_t len )
+{
+    std::snprintf( buffer, len, "Unknown error (%d)", ev );
+    return buffer;
+}
+
+#endif
+
+inline char const * system_category_message_win32( int ev, char * buffer, std::size_t len ) BOOST_NOEXCEPT
+{
+    if( len == 0 )
+    {
+        return buffer;
+    }
+
+    if( len == 1 )
+    {
+        buffer[0] = 0;
+        return buffer;
+    }
+
+#if defined(__GNUC__)
+# define BOOST_SYSTEM_ALLOCA __builtin_alloca
+#else
+# define BOOST_SYSTEM_ALLOCA _alloca
+#endif
+
+    wchar_t * wbuffer = static_cast<wchar_t*>( BOOST_SYSTEM_ALLOCA( len * sizeof( wchar_t ) ) );
+
+#undef BOOST_SYSTEM_ALLOCA
+
+    using namespace boost::winapi;
+
+    DWORD_ retval = boost::winapi::FormatMessageW(
+        FORMAT_MESSAGE_FROM_SYSTEM_ | FORMAT_MESSAGE_IGNORE_INSERTS_,
+        NULL,
+        ev,
+        MAKELANGID_( LANG_NEUTRAL_, SUBLANG_DEFAULT_ ), // Default language
+        wbuffer,
+        static_cast<DWORD_>( len ),
+        NULL
+    );
+
+    if( retval == 0 )
+    {
+        return unknown_message_win32( ev, buffer, len );
+    }
+
+    int r = boost::winapi::WideCharToMultiByte( CP_ACP_, 0, wbuffer, -1, buffer, static_cast<int>( len ), NULL, NULL );
+
+    if( r == 0 )
+    {
+        return unknown_message_win32( ev, buffer, len );
+    }
+
+    --r; // exclude null terminator
+
+    while( r > 0 && ( buffer[ r-1 ] == '\n' || buffer[ r-1 ] == '\r' ) )
+    {
+        buffer[ --r ] = 0;
+    }
+
+    if( r > 0 && buffer[ r-1 ] == '.' )
+    {
+        buffer[ --r ] = 0;
+    }
+
+    return buffer;
+}
+
+struct local_free
+{
+    void * p_;
+
+    ~local_free()
+    {
+        boost::winapi::LocalFree( p_ );
+    }
+};
+
+inline std::string unknown_message_win32( int ev )
+{
+    char buffer[ 38 ];
+    return unknown_message_win32( ev, buffer, sizeof( buffer ) );
+}
+
 inline std::string system_category_message_win32( int ev )
 {
     using namespace boost::winapi;
 
-    std::wstring buf( 128, wchar_t() );
+    wchar_t * lpMsgBuf = 0;
 
-    for( ;; )
+    DWORD_ retval = boost::winapi::FormatMessageW(
+        FORMAT_MESSAGE_ALLOCATE_BUFFER_ | FORMAT_MESSAGE_FROM_SYSTEM_ | FORMAT_MESSAGE_IGNORE_INSERTS_,
+        NULL,
+        ev,
+        MAKELANGID_( LANG_NEUTRAL_, SUBLANG_DEFAULT_ ), // Default language
+        (LPWSTR_) &lpMsgBuf,
+        0,
+        NULL
+    );
+
+    if( retval == 0 )
     {
-        DWORD_ retval = boost::winapi::FormatMessageW(
-            FORMAT_MESSAGE_FROM_SYSTEM_ | FORMAT_MESSAGE_IGNORE_INSERTS_,
-            NULL,
-            ev,
-            MAKELANGID_( LANG_NEUTRAL_, SUBLANG_DEFAULT_ ), // Default language
-            &buf[0],
-            static_cast<DWORD_>( buf.size() ),
-            NULL
-        );
-
-        if( retval > 0 )
-        {
-            buf.resize(retval);
-            break;
-        }
-        else if( boost::winapi::GetLastError() != ERROR_INSUFFICIENT_BUFFER_ )
-        {
-            return "Unknown error";
-        }
-        else
-        {
-            buf.resize( buf.size() + buf.size() / 2 );
-        }
+        return unknown_message_win32( ev );
     }
 
-    int num_chars = static_cast<int>( buf.size() + 1 ) * 2;
+    local_free lf_ = { lpMsgBuf };
 
-    boost::winapi::LPSTR_ narrow_buffer =
-#if defined(__GNUC__)
-        (boost::winapi::LPSTR_)__builtin_alloca( num_chars );
-#else
-        (boost::winapi::LPSTR_)_alloca( num_chars );
-#endif
+    int r = boost::winapi::WideCharToMultiByte( CP_ACP_, 0, lpMsgBuf, -1, 0, 0, NULL, NULL );
 
-    if( boost::winapi::WideCharToMultiByte( CP_ACP_, 0, buf.c_str(), -1, narrow_buffer, num_chars, NULL, NULL ) == 0 )
+    if( r == 0 )
     {
-        return "Unknown error";
+        return unknown_message_win32( ev );
     }
 
-    std::string str( narrow_buffer );
+    std::string buffer( r, char() );
 
-    while( !str.empty() && ( str[ str.size() - 1 ] == '\n' || str[ str.size() - 1 ] == '\r' ) )
+    r = boost::winapi::WideCharToMultiByte( CP_ACP_, 0, lpMsgBuf, -1, &buffer[0], r, NULL, NULL );
+
+    if( r == 0 )
     {
-        str.erase( str.size() - 1 );
+        return unknown_message_win32( ev );
     }
 
-    if( str.size() && str[ str.size() - 1 ] == '.' )
+    --r; // exclude null terminator
+
+    while( r > 0 && ( buffer[ r-1 ] == '\n' || buffer[ r-1 ] == '\r' ) )
     {
-        str.erase( str.size() - 1 );
+        --r;
     }
 
-    return str;
+    if( r > 0 && buffer[ r-1 ] == '.' )
+    {
+        --r;
+    }
+
+    buffer.resize( r );
+
+    return buffer;
 }
 
 inline error_condition system_category_default_error_condition_win32( int ev ) BOOST_NOEXCEPT

include/boost/system/error_code.hpp

@@ -17,6 +17,7 @@
 #include <ostream>
 #include <string>
 #include <functional>
+#include <cstring>
 
 // TODO: undef these macros if not already defined
 #include <boost/cerrno.hpp>
@@ -195,9 +196,12 @@ protected:
 
 #else
 
-    ~error_category()
-    {
-    }
+    // We'd like to make the destructor protected, to make code that deletes
+    // an error_category* not compile; unfortunately, doing the below makes
+    // the destructor user-provided and hence breaks use after main, as the
+    // categories may get destroyed before code that uses them
+
+    // ~error_category() {}
 
 #endif
 
@@ -213,12 +217,13 @@ public:
 
     virtual const char * name() const BOOST_NOEXCEPT = 0;
 
-    virtual std::string message( int ev ) const = 0;
-
     virtual error_condition default_error_condition( int ev ) const BOOST_NOEXCEPT;
     virtual bool equivalent( int code, const error_condition & condition ) const BOOST_NOEXCEPT;
     virtual bool equivalent( const error_code & code, int condition ) const BOOST_NOEXCEPT;
 
+    virtual std::string message( int ev ) const = 0;
+    virtual char const * message( int ev, char * buffer, std::size_t len ) const BOOST_NOEXCEPT;
+
     BOOST_SYSTEM_CONSTEXPR bool operator==( const error_category & rhs ) const BOOST_NOEXCEPT
     {
         return rhs.id_ == 0? this == &rhs: id_ == rhs.id_;
@@ -281,6 +286,7 @@ public:
     }
 
     std::string message( int ev ) const;
+    char const * message( int ev, char * buffer, std::size_t len ) const BOOST_NOEXCEPT;
 };
 
 class BOOST_SYMBOL_VISIBLE system_error_category: public error_category
@@ -296,8 +302,10 @@ public:
         return "system";
     }
 
-    std::string message( int ev ) const;
     error_condition default_error_condition( int ev ) const BOOST_NOEXCEPT;
+
+    std::string message( int ev ) const;
+    char const * message( int ev, char * buffer, std::size_t len ) const BOOST_NOEXCEPT;
 };
 
 } // namespace detail
@@ -443,6 +451,11 @@ public:
         return m_cat->message( value() );
     }
 
+    char const * message( char * buffer, std::size_t len ) const BOOST_NOEXCEPT
+    {
+        return m_cat->message( value(), buffer, len );
+    }
+
 #if !defined(BOOST_NO_CXX11_EXPLICIT_CONVERSION_OPERATORS)
 
     BOOST_SYSTEM_CONSTEXPR explicit operator bool() const BOOST_NOEXCEPT  // true if error
@@ -483,7 +496,7 @@ public:
 
 #if defined(BOOST_SYSTEM_HAS_SYSTEM_ERROR)
 
-    operator std::error_condition () const BOOST_NOEXCEPT
+    operator std::error_condition () const
     {
         return std::error_condition( value(), category() );
     }
@@ -569,6 +582,11 @@ public:
         return m_cat->message( value() );
     }
 
+    char const * message( char * buffer, std::size_t len ) const BOOST_NOEXCEPT
+    {
+        return m_cat->message( value(), buffer, len );
+    }
+
 #if !defined(BOOST_NO_CXX11_EXPLICIT_CONVERSION_OPERATORS)
 
     BOOST_SYSTEM_CONSTEXPR explicit operator bool() const BOOST_NOEXCEPT  // true if error
@@ -610,7 +628,7 @@ public:
 
 #if defined(BOOST_SYSTEM_HAS_SYSTEM_ERROR)
 
-    operator std::error_code () const BOOST_NOEXCEPT
+    operator std::error_code () const
     {
         return std::error_code( value(), category() );
     }
@@ -760,6 +778,47 @@ inline bool error_category::equivalent( const error_code & code, int condition )
     return *this == code.category() && code.value() == condition;
 }
 
+inline char const * error_category::message( int ev, char * buffer, std::size_t len ) const BOOST_NOEXCEPT
+{
+    if( len == 0 )
+    {
+        return buffer;
+    }
+
+    if( len == 1 )
+    {
+        buffer[0] = 0;
+        return buffer;
+    }
+
+#if !defined(BOOST_NO_EXCEPTIONS)
+    try
+#endif
+    {
+        std::string m = this->message( ev );
+
+# if defined( BOOST_MSVC )
+#  pragma warning( push )
+#  pragma warning( disable: 4996 )
+# endif
+
+        std::strncpy( buffer, m.c_str(), len - 1 );
+        buffer[ len-1 ] = 0;
+
+# if defined( BOOST_MSVC )
+#  pragma warning( pop )
+# endif
+
+        return buffer;
+    }
+#if !defined(BOOST_NO_EXCEPTIONS)
+    catch( ... )
+    {
+        return "Message text unavailable";
+    }
+#endif
+}
+
 } // namespace system
 
 } // namespace boost
@@ -773,34 +832,49 @@ inline std::string boost::system::detail::generic_error_category::message( int e
     return generic_error_category_message( ev );
 }
 
+inline char const * boost::system::detail::generic_error_category::message( int ev, char * buffer, std::size_t len ) const BOOST_NOEXCEPT
+{
+    return generic_error_category_message( ev, buffer, len );
+}
+
 // system_error_category implementation
 
 #if defined(BOOST_WINDOWS_API)
 
 #include <boost/system/detail/system_category_win32.hpp>
 
+inline boost::system::error_condition boost::system::detail::system_error_category::default_error_condition( int ev ) const BOOST_NOEXCEPT
+{
+    return system_category_default_error_condition_win32( ev );
+}
+
 inline std::string boost::system::detail::system_error_category::message( int ev ) const
 {
     return system_category_message_win32( ev );
 }
 
-inline boost::system::error_condition boost::system::detail::system_error_category::default_error_condition( int ev ) const BOOST_NOEXCEPT
+inline char const * boost::system::detail::system_error_category::message( int ev, char * buffer, std::size_t len ) const BOOST_NOEXCEPT
 {
-    return system_category_default_error_condition_win32( ev );
+    return system_category_message_win32( ev, buffer, len );
 }
 
 #else // #if defined(BOOST_WINDOWS_API)
 
 #include <boost/system/detail/system_category_posix.hpp>
 
+inline boost::system::error_condition boost::system::detail::system_error_category::default_error_condition( int ev ) const BOOST_NOEXCEPT
+{
+    return system_category_default_error_condition_posix( ev );
+}
+
 inline std::string boost::system::detail::system_error_category::message( int ev ) const
 {
     return generic_error_category_message( ev );
 }
 
-inline boost::system::error_condition boost::system::detail::system_error_category::default_error_condition( int ev ) const BOOST_NOEXCEPT
+inline char const * boost::system::detail::system_error_category::message( int ev, char * buffer, std::size_t len ) const BOOST_NOEXCEPT
 {
-    return system_category_default_error_condition_posix( ev );
+    return generic_error_category_message( ev, buffer, len );
 }
 
 #endif // #if defined(BOOST_WINDOWS_API)

test/Jamfile.v2

@@ -1,6 +1,7 @@
 # Boost System Library test Jamfile
 
 # Copyright Beman Dawes 2003, 2006
+# Copyright 2017, 2018 Peter Dimov
 
 # Distributed under the Boost Software License, Version 1.0.
 # See accompanying file LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt
@@ -13,7 +14,6 @@ import os ;
 project
     : requirements
       <library>/boost/system//boost_system
-      <toolset>msvc:<asynch-exceptions>on
     ;
 
    lib throw_test : throw_test.cpp : <link>shared:<define>THROW_DYN_LINK=1 ;
@@ -98,33 +98,35 @@ else
    }
 }
 
-   test-suite "system"
-       : [ system-run error_code_test.cpp ]
-         [ system-run error_code_user_test.cpp ]
-         [ system-run system_error_test.cpp ]
-         [ run dynamic_link_test.cpp throw_test
-           :  :  : <link>shared : throw_test_shared
-         ]
-         [ system-run initialization_test.cpp ]
-         [ run header_only_test.cpp
-           :  :  : -<library>/boost/system//boost_system
-         ]
-         [ run header_only_test.cpp
-           :  :  : -<library>/boost/system//boost_system <define>BOOST_NO_ANSI_APIS : header_only_test_no_ansi
-         ]
-         [ run config_test.cpp
-           :  :  : <test-info>always_show_run_output
-         ]
-         [ system-run- std_interop_test.cpp ]
-         [ system-run std_mismatch_test.cpp ]
-         [ system-run single_instance_test.cpp single_instance_1.cpp single_instance_2.cpp ]
-         [ run single_instance_test.cpp single_instance_lib1 single_instance_lib2 : : : <link>static : single_instance_lib_static ]
-         [ run single_instance_test.cpp single_instance_lib1 single_instance_lib2 : : : <link>shared : single_instance_lib_shared ]
-         [ system-run before_main_test.cpp ]
-         [ run-fail throws_assign_fail.cpp ]
-         [ system-run- constexpr_test.cpp ]
-         [ system-run win32_hresult_test.cpp ]
-         ;
+system-run error_code_test.cpp ;
+system-run error_code_user_test.cpp ;
+system-run system_error_test.cpp ;
+
+run dynamic_link_test.cpp throw_test :  :  : <link>shared : throw_test_shared ;
+
+system-run initialization_test.cpp ;
+
+run header_only_test.cpp : : : -<library>/boost/system//boost_system ;
+run header_only_test.cpp : : : -<library>/boost/system//boost_system <define>BOOST_NO_ANSI_APIS : header_only_test_no_ansi ;
+
+run config_test.cpp : : : <test-info>always_show_run_output ;
+
+system-run- std_interop_test.cpp ;
+system-run std_mismatch_test.cpp ;
+
+system-run single_instance_test.cpp single_instance_1.cpp single_instance_2.cpp ;
+run single_instance_test.cpp single_instance_lib1 single_instance_lib2 : : : <link>static : single_instance_lib_static ;
+run single_instance_test.cpp single_instance_lib1 single_instance_lib2 : : : <link>shared : single_instance_lib_shared ;
+
+system-run before_main_test.cpp ;
+run-fail throws_assign_fail.cpp ;
+system-run- constexpr_test.cpp ;
+system-run win32_hresult_test.cpp ;
+
+system-run error_category_test.cpp ;
+system-run generic_category_test.cpp ;
+system-run system_category_test.cpp ;
+system-run after_main_test.cpp ;
 
 # Quick (CI) test
 run quick.cpp ;

test/after_main_test.cpp

@@ -0,0 +1,30 @@
+
+// Copyright 2018 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+
+#include <boost/system/error_code.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <boost/core/quick_exit.hpp>
+#include <cerrno>
+
+using namespace boost::system;
+
+struct Z
+{
+    ~Z()
+    {
+        BOOST_TEST_CSTR_EQ( generic_category().name(), "generic" );
+        BOOST_TEST_CSTR_EQ( system_category().name(), "system" );
+
+        boost::quick_exit( boost::report_errors() );
+    }
+};
+
+static Z z;
+
+static error_code e1( 1, system_category() );
+static error_code e2( ENOENT, generic_category() );
+
+int main()
+{
+}

test/error_category_test.cpp

@@ -0,0 +1,82 @@
+
+// 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
+
+// Avoid spurious VC++ warnings
+# define _CRT_SECURE_NO_WARNINGS
+
+#include <boost/system/error_code.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <cstdio>
+
+//
+
+namespace sys = boost::system;
+
+class user_category: public sys::error_category
+{
+public:
+
+    virtual const char * name() const BOOST_NOEXCEPT
+    {
+        return "user";
+    }
+
+    virtual std::string message( int ev ) const
+    {
+        char buffer[ 256 ];
+        std::sprintf( buffer, "user message %d", ev );
+
+        return buffer;
+    }
+
+    using sys::error_category::message;
+};
+
+static user_category s_cat_1;
+static user_category s_cat_2;
+
+int main()
+{
+    // default_error_condition
+
+    BOOST_TEST( s_cat_1.default_error_condition( 1 ) == sys::error_condition( 1, s_cat_1 ) );
+    BOOST_TEST( s_cat_2.default_error_condition( 2 ) == sys::error_condition( 2, s_cat_2 ) );
+
+    // equivalent
+
+    BOOST_TEST( s_cat_1.equivalent( 1, sys::error_condition( 1, s_cat_1 ) ) );
+    BOOST_TEST( !s_cat_1.equivalent( 1, sys::error_condition( 2, s_cat_1 ) ) );
+    BOOST_TEST( !s_cat_1.equivalent( 1, sys::error_condition( 2, s_cat_2 ) ) );
+
+    // the other equivalent
+
+    BOOST_TEST( s_cat_1.equivalent( sys::error_code( 1, s_cat_1 ), 1 ) );
+    BOOST_TEST( !s_cat_1.equivalent( sys::error_code( 1, s_cat_1 ), 2 ) );
+    BOOST_TEST( !s_cat_1.equivalent( sys::error_code( 1, s_cat_2 ), 1 ) );
+
+    // message
+
+    {
+        char buffer[ 256 ];
+        BOOST_TEST_CSTR_EQ( s_cat_1.message( 1, buffer, sizeof( buffer ) ), s_cat_1.message( 1 ).c_str() );
+    }
+
+    {
+        char buffer[ 4 ];
+        BOOST_TEST_CSTR_EQ( s_cat_1.message( 1, buffer, sizeof( buffer ) ), "use" );
+    }
+
+    // ==
+
+    BOOST_TEST_NOT( s_cat_1 == s_cat_2 );
+    BOOST_TEST( s_cat_1 != s_cat_2 );
+
+    return boost::report_errors();
+}

test/generic_category_test.cpp

@@ -0,0 +1,41 @@
+
+// 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
+
+// Avoid spurious VC++ warnings
+# define _CRT_SECURE_NO_WARNINGS
+
+#include <boost/system/error_code.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <cstring>
+
+//
+
+namespace sys = boost::system;
+
+int main()
+{
+    sys::error_category const & cat = sys::generic_category();
+
+    // message
+
+    for( int i = -2; i < 1024; ++i )
+    {
+        {
+            BOOST_TEST_CSTR_EQ( cat.message( i ).c_str(), std::strerror( i ) );
+        }
+
+        {
+            char buffer[ 256 ];
+            BOOST_TEST_CSTR_EQ( cat.message( i, buffer, sizeof( buffer ) ), std::strerror( i ) );
+        }
+    }
+
+    return boost::report_errors();
+}

test/system_category_test.cpp

@@ -0,0 +1,116 @@
+
+// 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
+
+// Avoid spurious VC++ warnings
+# define _CRT_SECURE_NO_WARNINGS
+
+#include <boost/system/error_code.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <cstring>
+#include <cstdio>
+
+//
+
+#if defined(BOOST_WINDOWS_API)
+
+#include <windows.h>
+
+std::string sys_strerror( int ev )
+{
+    void * lpMsgBuf = 0;
+
+    DWORD retval = FormatMessageA(
+        FORMAT_MESSAGE_ALLOCATE_BUFFER |
+        FORMAT_MESSAGE_FROM_SYSTEM |
+        FORMAT_MESSAGE_IGNORE_INSERTS,
+        NULL,
+        ev,
+        MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
+        (LPSTR) &lpMsgBuf,
+        0,
+        NULL
+    );
+
+    struct local_free
+    {
+        void * p_;
+
+        ~local_free()
+        {
+            LocalFree( p_ );
+        }
+    };
+
+    local_free lf_ = { lpMsgBuf };
+
+    if( retval == 0 )
+    {
+        char buffer[ 38 ];
+
+        std::sprintf( buffer, "Unknown error (%d)", ev );
+        return buffer;
+    }
+
+    std::string str( static_cast<char const*>( lpMsgBuf ) );
+
+    while( !str.empty() && (str[str.size()-1] == '\n' || str[str.size()-1] == '\r') )
+    {
+        str.erase( str.size()-1 );
+    }
+
+    if( !str.empty() && str[str.size()-1] == '.' )
+    {
+        str.erase( str.size()-1 );
+    }
+
+    return str;
+}
+
+#else
+
+std::string sys_strerror( int ev )
+{
+    return std::strerror( ev );
+}
+
+#endif
+
+//
+
+namespace sys = boost::system;
+
+static void test_message( sys::error_category const & cat, int ev )
+{
+    BOOST_TEST_EQ( cat.message( ev ), sys_strerror( ev ) );
+
+    char buffer[ 2048 ]; // yes, really
+    BOOST_TEST_CSTR_EQ( cat.message( ev, buffer, sizeof( buffer ) ), sys_strerror( ev ).c_str() );
+}
+
+int main()
+{
+    sys::error_category const & cat = sys::system_category();
+
+    // message
+
+    for( int i = -2; i < 1024; ++i )
+    {
+        test_message( cat, i );
+    }
+
+    test_message( cat, 5810 );
+
+    for( int i = 10000; i < 11032; ++i )
+    {
+        test_message( cat, i );
+    }
+
+    return boost::report_errors();
+}