From f43293f451cc0aa0a5666596f7d18c7802159c75 Mon Sep 17 00:00:00 2001 From: Peter Dimov Date: Sun, 13 Jun 2021 05:24:30 +0300 Subject: [PATCH 1/4] Increase ToC levels --- doc/system.adoc | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/doc/system.adoc b/doc/system.adoc index f135c08..2aaaed3 100644 --- a/doc/system.adoc +++ b/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 From 25eaf0fdae8674a6364c40ba9a903837b7f98211 Mon Sep 17 00:00:00 2001 From: Peter Dimov Date: Sun, 13 Jun 2021 05:58:16 +0300 Subject: [PATCH 2/4] Document comparisons as inline friends; use value() and category() instead of val_ and cat_; add subheadings --- doc/system/reference.adoc | 226 +++++++++++++++++++++++--------------- 1 file changed, 137 insertions(+), 89 deletions(-) diff --git a/doc/system/reference.adoc b/doc/system/reference.adoc index 5dbf889..43e7988 100644 --- a/doc/system/reference.adoc +++ b/doc/system/reference.adoc @@ -165,28 +165,15 @@ namespace boost { // 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; @@ -251,9 +238,13 @@ 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 +388,42 @@ 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()( this, &rhs )`. +** Otherwise, `std::less()( &lhs, &rhs )`. + +#### Conversions ``` operator std::error_category const & () const; @@ -502,13 +498,19 @@ 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_; - }; } } @@ -522,7 +524,7 @@ 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 +532,7 @@ constexpr error_code( int val, const error_category & cat ) noexcept; [none] * {blank} + -Ensures: :: `val_ == val`; `cat_ == &cat`. +Ensures: :: `value() == val`; `category() == cat`. ``` template @@ -550,7 +552,7 @@ constexpr void assign( int val, const error_category & cat ) noexcept; [none] * {blank} + -Ensures: :: `val_ == val`; `cat_ == &cat`. +Ensures: :: `value() == val`; `category() == cat`. ``` template @@ -569,7 +571,7 @@ constexpr void clear() noexcept; * {blank} + Ensures: :: - `val_ == 0`; `*cat_ == system_category()`. + `value() == 0`; `category() == system_category()`. #### Observers @@ -579,7 +581,7 @@ constexpr int value() const noexcept; [none] * {blank} + -Returns: :: `val_`. +Returns: :: the error value. ``` constexpr const error_category & category() const noexcept; @@ -587,7 +589,7 @@ constexpr const error_category & category() const noexcept; [none] * {blank} + -Returns: :: `*cat_`. +Returns: :: the error category. ``` error_condition default_error_condition() const noexcept; @@ -595,7 +597,7 @@ 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 +605,7 @@ 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 +613,7 @@ 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 +621,7 @@ constexpr bool failed() const noexcept; [none] * {blank} + -Returns: :: `cat_\->failed( val_ )`. +Returns: :: `category().failed( value() )`. ``` constexpr explicit operator bool() const noexcept; @@ -627,7 +629,40 @@ 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; @@ -636,7 +671,7 @@ operator std::error_code() const; * {blank} + Returns: :: - `std::error_code( val_, *cat_ )`. + `std::error_code( value(), category() )`. ### Class error_condition @@ -675,13 +710,19 @@ namespace boost { 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; - - private: // exposition only - - int val_; - const error_category * cat_; - }; } } @@ -695,7 +736,7 @@ 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; @@ -703,7 +744,7 @@ constexpr error_condition( int val, const error_category & cat ) noexcept; [none] * {blank} + -Ensures: :: `val_ == val`; `cat_ == &cat`. +Ensures: :: `value() == val`; `category() == cat`. ``` template @@ -724,7 +765,7 @@ constexpr void assign( int val, const error_category & cat ) noexcept; [none] * {blank} + -Ensures: :: `val_ == val`; `cat_ == &cat`. +Ensures: :: `value() == val`; `category() == cat`. ``` template @@ -743,7 +784,7 @@ constexpr void clear() noexcept; * {blank} + Ensures: :: - `val_ == 0`; `*cat_ == generic_category()`. + `value() == 0`; `category() == generic_category()`. #### Observers @@ -753,7 +794,7 @@ constexpr int value() const noexcept; [none] * {blank} + -Returns: :: `val_`. +Returns: :: the error value. ``` constexpr const error_category & category() const noexcept; @@ -761,7 +802,7 @@ constexpr const error_category & category() const noexcept; [none] * {blank} + -Returns: :: `*cat_`. +Returns: :: the error category. ``` std::string message() const; @@ -769,7 +810,7 @@ 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; @@ -777,7 +818,7 @@ 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; @@ -785,7 +826,7 @@ constexpr bool failed() const noexcept; [none] * {blank} + -Returns: :: `cat_\->failed( val_ )`. +Returns: :: `category().failed( value() )`. ``` constexpr explicit operator bool() const noexcept; @@ -793,7 +834,40 @@ constexpr explicit operator bool() const noexcept; [none] * {blank} + -Returns: :: `failed()`. +Returns: :: + `failed()`. + +#### Comparisons + +``` +friend constexpr bool operator==( const error_condition & lhs, + const error_condition & rhs ) noexcept; +``` +[none] +* {blank} ++ +Returns: :: `lhs.value() == rhs.value() && lhs.category() == rhs.category()`. + +``` +friend constexpr bool operator!=( const error_condition & lhs, + const error_condition & rhs ) noexcept; +``` +[none] +* {blank} ++ +Returns: :: `!( lhs == rhs )`. + +``` +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())`. + +#### Conversions ``` operator std::error_condition() const; @@ -802,21 +876,10 @@ operator std::error_condition() const; * {blank} + Returns: :: - `std::error_condition( val_, *cat_ )`. + `std::error_condition( value(), category() )`. ### Nonmember functions -``` -constexpr bool operator==( const error_code & lhs, - const error_code & rhs ) noexcept; -constexpr bool operator==( const error_condition & lhs, - const error_condition & rhs ) noexcept; -``` -[none] -* {blank} -+ -Returns: :: `lhs.value() == rhs.value() && lhs.category() == rhs.category()`. - ``` bool operator==( const error_code & code, const error_condition & condition ) noexcept; @@ -826,13 +889,9 @@ bool operator==( const error_condition & condition, [none] * {blank} + -Returns: :: `code.category().equivalent( code.value(), condition ) || condition.category().equivalent( code, condition.value() )`. +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, - const error_condition & rhs ) noexcept; bool operator!=( const error_code & code, const error_condition & condition ) noexcept; bool operator!=( const error_condition & condition, @@ -843,17 +902,6 @@ 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, - const error_condition & rhs ) noexcept; -``` -[none] -* {blank} -+ -Returns: :: `lhs.category() < rhs.category() || ( lhs.category() == rhs.category() && lhs.value() < rhs.value() )`. - ``` constexpr error_code make_error_code( errc::errc_t e ) noexcept; ``` From 75d52875585c4717191218d7aff5a457583722d9 Mon Sep 17 00:00:00 2001 From: Peter Dimov Date: Sun, 13 Jun 2021 05:59:04 +0300 Subject: [PATCH 3/4] Update copyright --- doc/system/copyright.adoc | 4 ++-- doc/system/reference.adoc | 2 +- 2 files changed, 3 insertions(+), 3 deletions(-) diff --git a/doc/system/copyright.adoc b/doc/system/copyright.adoc index 6f77e69..2349336 100644 --- a/doc/system/copyright.adoc +++ b/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]. diff --git a/doc/system/reference.adoc b/doc/system/reference.adoc index 43e7988..a407b88 100644 --- a/doc/system/reference.adoc +++ b/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. From 1caaacff573137a94024548e4b54f964cc945e6f Mon Sep 17 00:00:00 2001 From: Peter Dimov Date: Sun, 13 Jun 2021 06:58:48 +0300 Subject: [PATCH 4/4] Split reference into headers --- doc/system/reference.adoc | 312 +++++++++++++++++++++++++------------- 1 file changed, 206 insertions(+), 106 deletions(-) diff --git a/doc/system/reference.adoc b/doc/system/reference.adoc index a407b88..4c02f74 100644 --- a/doc/system/reference.adoc +++ b/doc/system/reference.adoc @@ -48,31 +48,53 @@ the old names, but will provide them when the macro `BOOST_SYSTEM_ENABLE_DEPRECA |`native_ecat`|`system_category()` |=== -## +## -### 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 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. + +## + +### is_error_condition_enum + +``` +namespace boost { + namespace system { + template 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. + +## + +### errc + +``` +namespace boost { + namespace system { namespace errc { enum errc_t @@ -163,39 +185,80 @@ namespace boost { template<> struct is_error_condition_enum { static const bool value = true; }; - // 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; - constexpr error_code make_error_code( errc::errc_t e ) noexcept; constexpr error_condition make_error_condition( errc::errc_t e ) noexcept; - template - std::basic_ostream& - operator<<( basic_ostream& 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 `` -macro shown in the above synopsis. +The predefined enumeration type `errc::errc_t` provides named constants +corresponding to the values of the `` 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 +} +``` + +## + +### 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. @@ -434,7 +497,19 @@ operator std::error_category const & () const; Returns: :: A reference to an `std::error_category` object corresponding to `*this`. -### Predefined Categories +## + +### system_category + +``` +namespace boost { + namespace system { + + constexpr const error_category & system_category() noexcept; + + } // namespace system +} // namespace boost +``` ``` constexpr const error_category & system_category() noexcept; @@ -442,8 +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. + +## + +### generic_category + +``` +namespace boost { + namespace system { + + constexpr const error_category & generic_category() noexcept; + + } // namespace system +} // namespace boost +``` ``` constexpr const error_category & generic_category() noexcept; @@ -451,10 +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 +## + +### 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 @@ -512,6 +603,25 @@ namespace boost { operator std::error_code() const; }; + + // 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 + std::basic_ostream& + operator<<( basic_ostream& os, const error_code & ec ); + + std::size_t hash_value( const error_code & ec ); + } } ``` @@ -673,7 +783,53 @@ operator std::error_code() const; Returns: :: `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 + std::basic_ostream& + operator<<( basic_ostream& 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`. + +## + +### error_condition ``` namespace boost { @@ -878,67 +1034,7 @@ operator std::error_condition() const; Returns: :: `std::error_condition( value(), category() )`. -### Nonmember functions - -``` -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 )`. - -``` -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 - std::basic_ostream& - operator<<( basic_ostream& 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`. - -## +## ### Class system_error @@ -1015,4 +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()`. + +## + +This convenience header includes all the headers previously described.