Update system_error constructors

doc/system/changes.adoc

@@ -8,6 +8,10 @@ https://www.boost.org/LICENSE_1_0.txt
 # Revision History
 :idprefix:
 
+## Changes in Boost 1.79
+
+* Added a `throw_exception_from_error` overload for `std::error_code`.
+
 ## Changes in Boost 1.78
 
 * Added support for source locations to `error_code`.

doc/system/reference.adoc

@@ -1455,6 +1455,7 @@ namespace system {
 // throw_exception_from_error
 
 BOOST_NORETURN inline void throw_exception_from_error( error_code const & e );
+BOOST_NORETURN inline void throw_exception_from_error( std::error_code const & e );
 
 // in_place_*
 
@@ -1494,6 +1495,15 @@ BOOST_NORETURN inline void throw_exception_from_error( error_code const & e );
 Effects: ::
   `boost::throw_exception( system_error( e ) )`.
 
+```
+BOOST_NORETURN inline void throw_exception_from_error( std::error_code const & e );
+```
+[none]
+* {blank}
++
+Effects: ::
+  `boost::throw_exception( std::system_error( e ) )`.
+
 ### result<T, E>
 
 `result<T, E>` stores either a value of type `T`, or an error of type `E`. `E` defaults

include/boost/system/result.hpp

@@ -16,6 +16,7 @@
 #include <type_traits>
 #include <utility>
 #include <iosfwd>
+#include <system_error>
 
 //
 
@@ -26,11 +27,25 @@ namespace system
 
 // throw_exception_from_error
 
-BOOST_NORETURN inline void throw_exception_from_error( error_code const & e )
+#if defined(__GNUC__) && __GNUC__ >= 7 && __GNUC__ <= 8
+# pragma GCC diagnostic push
+# pragma GCC diagnostic ignored "-Wattributes"
+#endif
+
+BOOST_NORETURN BOOST_NOINLINE inline void throw_exception_from_error( error_code const & e )
 {
     boost::throw_exception( system_error( e ) );
 }
 
+BOOST_NORETURN BOOST_NOINLINE inline void throw_exception_from_error( std::error_code const & e )
+{
+    boost::throw_exception( std::system_error( e ) );
+}
+
+#if defined(__GNUC__) && __GNUC__ >= 7 && __GNUC__ <= 8
+# pragma GCC diagnostic pop
+#endif
+
 // in_place_*
 
 using in_place_value_t = variant2::in_place_index_t<0>;

include/boost/system/system_error.hpp

@@ -23,46 +23,25 @@ private:
 
     error_code code_;
 
-private:
-
-    static std::string build_message( char const * prefix, error_code const & ec )
-    {
-        std::string r;
-
-        if( prefix )
-        {
-            r += prefix;
-            r += ": ";
-        }
-
-        r += ec.what();
-        return r;
-    }
-
-    static std::string build_message( char const * prefix, int ev, error_category const & cat )
-    {
-        return build_message( prefix, error_code( ev, cat ) );
-    }
-
 public:
 
-    explicit system_error( error_code const & ec )
-      : std::runtime_error( build_message( 0, ec ) ), code_( ec ) {}
+    explicit system_error( error_code const & ec ):
+        std::runtime_error( ec.what() ), code_( ec ) {}
 
-    system_error( error_code const & ec, std::string const & prefix )
-      : std::runtime_error( build_message( prefix.c_str(), ec ) ), code_( ec ) {}
+    system_error( error_code const & ec, std::string const & prefix ):
+        std::runtime_error( prefix + ": " + ec.what() ), code_( ec ) {}
 
-    system_error( error_code const & ec, char const * prefix )
-      : std::runtime_error( build_message( prefix, ec ) ), code_( ec ) {}
+    system_error( error_code const & ec, char const * prefix ):
+        std::runtime_error( std::string( prefix ) + ": " + ec.what() ), code_( ec ) {}
 
-    system_error( int ev, error_category const & ecat )
-      : std::runtime_error( build_message( 0, ev, ecat ) ), code_( ev, ecat ) {}
+    system_error( int ev, error_category const & ecat ):
+        std::runtime_error( error_code( ev, ecat ).what() ), code_( ev, ecat ) {}
 
-    system_error( int ev, error_category const & ecat, std::string const & prefix )
-      : std::runtime_error( build_message( prefix.c_str(), ev, ecat ) ), code_( ev, ecat ) {}
+    system_error( int ev, error_category const & ecat, std::string const & prefix ):
+        std::runtime_error( prefix + ": " + error_code( ev, ecat ).what() ), code_( ev, ecat ) {}
 
-    system_error( int ev, error_category const & ecat, char const * prefix )
-      : std::runtime_error( build_message( prefix, ev, ecat ) ), code_( ev, ecat ) {}
+    system_error( int ev, error_category const & ecat, char const * prefix ):
+        std::runtime_error( std::string( prefix ) + ": " + error_code( ev, ecat ).what() ), code_( ev, ecat ) {}
 
     error_code code() const BOOST_NOEXCEPT
     {

test/result_value_access.cpp

@@ -1,10 +1,11 @@
-// Copyright 2017, 2021 Peter Dimov.
+// Copyright 2017, 2021, 2022 Peter Dimov.
 // Distributed under the Boost Software License, Version 1.0.
 // https://www.boost.org/LICENSE_1_0.txt
 
 #include <boost/system/result.hpp>
 #include <boost/core/lightweight_test.hpp>
 #include <boost/core/lightweight_test_trait.hpp>
+#include <system_error>
 
 using namespace boost::system;
 
@@ -165,6 +166,22 @@ int main()
         BOOST_TEST_EQ( result<int>( ec ).operator->(), static_cast<int*>(0) );
     }
 
+    {
+        auto ec = make_error_code( std::errc::invalid_argument );
+
+        result<int, std::error_code> const r( ec );
+
+        BOOST_TEST( !r.has_value() );
+        BOOST_TEST( r.has_error() );
+
+        BOOST_TEST_NOT( r );
+        BOOST_TEST( !r );
+
+        BOOST_TEST_THROWS( r.value(), std::system_error );
+
+        BOOST_TEST_EQ( r.operator->(), static_cast<int*>(0) );
+    }
+
     {
         result<X> r( 1 );
 
@@ -341,5 +358,21 @@ int main()
         BOOST_TEST_EQ( result<void>( ec ).operator->(), static_cast<void*>(0) );
     }
 
+    {
+        auto ec = make_error_code( std::errc::invalid_argument );
+
+        result<void, std::error_code> const r( ec );
+
+        BOOST_TEST( !r.has_value() );
+        BOOST_TEST( r.has_error() );
+
+        BOOST_TEST_NOT( r );
+        BOOST_TEST( !r );
+
+        BOOST_TEST_THROWS( r.value(), std::system_error );
+
+        BOOST_TEST_EQ( r.operator->(), static_cast<void*>(0) );
+    }
+
     return boost::report_errors();
 }

test/system_error_test3.cpp

@@ -1,4 +1,4 @@
-// Copyright 2021 Peter Dimov
+// Copyright 2021, 2022 Peter Dimov
 // Distributed under the Boost Software License, Version 1.0
 // https://www.boost.org/LICENSE_1_0.txt
 
@@ -14,22 +14,36 @@ int main()
         sys::error_code ec( 5, sys::generic_category() );
         sys::system_error x1( ec );
 
-		BOOST_TEST_EQ( std::string( x1.what() ), ec.what() );
+        BOOST_TEST_EQ( std::string( x1.what() ), ec.what() );
     }
 
     {
-        BOOST_STATIC_CONSTEXPR boost::source_location loc = BOOST_CURRENT_LOCATION;
-
-        sys::error_code ec( 5, sys::system_category(), &loc );
+        sys::error_code ec( 5, sys::generic_category() );
         sys::system_error x1( ec, "prefix" );
 
         BOOST_TEST_EQ( std::string( x1.what() ), "prefix: " + ec.what() );
     }
 
     {
-        sys::system_error x1( 5, sys::generic_category() );
+        sys::error_code ec( 5, sys::generic_category() );
+        sys::system_error x1( ec, std::string( "prefix2" ) );
 
-        BOOST_TEST_EQ( std::string( x1.what() ), sys::error_code( 5, sys::generic_category() ).what() );
+        BOOST_TEST_EQ( std::string( x1.what() ), "prefix2: " + ec.what() );
+    }
+
+    {
+        BOOST_STATIC_CONSTEXPR boost::source_location loc = BOOST_CURRENT_LOCATION;
+
+        sys::error_code ec( 5, sys::generic_category(), &loc );
+        sys::system_error x1( ec, "prefix3" );
+
+        BOOST_TEST_EQ( std::string( x1.what() ), "prefix3: " + ec.what() );
+    }
+
+    {
+        sys::system_error x1( 5, sys::system_category() );
+
+        BOOST_TEST_EQ( std::string( x1.what() ), sys::error_code( 5, sys::system_category() ).what() );
     }
 
     {
@@ -38,5 +52,11 @@ int main()
         BOOST_TEST_EQ( std::string( x1.what() ), "prefix: " + sys::error_code( 5, sys::system_category() ).what() );
     }
 
+    {
+        sys::system_error x1( 5, sys::system_category(), std::string( "prefix2" ) );
+
+        BOOST_TEST_EQ( std::string( x1.what() ), "prefix2: " + sys::error_code( 5, sys::system_category() ).what() );
+    }
+
     return boost::report_errors();
 }