From eefcc5dcf6fa71968aa51925df736729f1f0c507 Mon Sep 17 00:00:00 2001
From: Peter Dimov <pdimov@gmail.com>
Date: Sat, 2 Oct 2021 14:41:27 +0300
Subject: [PATCH] Add error_code::what

---
 include/boost/system/detail/error_code.hpp | 17 ++++
 test/CMakeLists.txt                        |  1 +
 test/Jamfile.v2                            |  1 +
 test/ec_what_test.cpp                      | 91 ++++++++++++++++++++++
 4 files changed, 110 insertions(+)
 create mode 100644 test/ec_what_test.cpp

diff --git a/include/boost/system/detail/error_code.hpp b/include/boost/system/detail/error_code.hpp
index fb79150..494167c 100644
--- a/include/boost/system/detail/error_code.hpp
+++ b/include/boost/system/detail/error_code.hpp
@@ -602,6 +602,23 @@ public:
     {
         return os << ec.to_string();
     }
+
+    std::string what() const
+    {
+        std::string r = message();
+
+        r += " [";
+        r += to_string();
+
+        if( has_location() )
+        {
+            r += " at ";
+            r += location().to_string();
+        }
+
+        r += "]";
+        return r;
+    }
 };
 
 inline std::size_t hash_value( error_code const & ec )
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 6f31850..902feff 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -107,6 +107,7 @@ boost_test(TYPE run SOURCES system_error_test2.cpp)
 boost_test(TYPE run SOURCES std_interop_test10.cpp)
 
 boost_test(TYPE run SOURCES ec_location_test2.cpp)
+boost_test(TYPE run SOURCES ec_what_test.cpp)
 
 # result
 
diff --git a/test/Jamfile.v2 b/test/Jamfile.v2
index 33dec94..75f6684 100644
--- a/test/Jamfile.v2
+++ b/test/Jamfile.v2
@@ -129,6 +129,7 @@ run system_error_test2.cpp ;
 run std_interop_test10.cpp ;
 
 run ec_location_test2.cpp ;
+run ec_what_test.cpp ;
 
 # result
 
diff --git a/test/ec_what_test.cpp b/test/ec_what_test.cpp
new file mode 100644
index 0000000..35c1e03
--- /dev/null
+++ b/test/ec_what_test.cpp
@@ -0,0 +1,91 @@
+// Copyright 2020, 2021 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// http://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/system/error_code.hpp>
+#include <boost/system/generic_category.hpp>
+#include <boost/system/system_category.hpp>
+#include <boost/core/lightweight_test.hpp>
+
+namespace sys = boost::system;
+
+int main()
+{
+    {
+        sys::error_code ec;
+
+        BOOST_TEST_EQ( ec.value(), 0 );
+        BOOST_TEST( ec.category() == sys::system_category() );
+
+        BOOST_TEST_EQ( ec.what(), ec.message() + " [system:0]" );
+    }
+
+    {
+        sys::error_code ec( 5, sys::generic_category() );
+
+        BOOST_TEST_EQ( ec.value(), 5 );
+        BOOST_TEST( ec.category() == sys::generic_category() );
+
+        BOOST_TEST_EQ( ec.what(), ec.message() + " [generic:5]" );
+    }
+
+    {
+        sys::error_code ec( 5, sys::system_category() );
+
+        BOOST_TEST_EQ( ec.value(), 5 );
+        BOOST_TEST( ec.category() == sys::system_category() );
+
+        BOOST_TEST_EQ( ec.what(), ec.message() + " [system:5]" );
+    }
+
+    {
+        BOOST_STATIC_CONSTEXPR boost::source_location loc = BOOST_CURRENT_LOCATION;
+
+        sys::error_code ec( 5, sys::generic_category(), &loc );
+
+        BOOST_TEST_EQ( ec.value(), 5 );
+        BOOST_TEST( ec.category() == sys::generic_category() );
+        BOOST_TEST_EQ( &ec.location(), &loc );
+
+        BOOST_TEST_EQ( ec.what(), ec.message() + " [generic:5 at " + loc.to_string() + "]" );
+    }
+
+    {
+        BOOST_STATIC_CONSTEXPR boost::source_location loc = BOOST_CURRENT_LOCATION;
+
+        sys::error_code ec( 5, sys::system_category(), &loc );
+
+        BOOST_TEST_EQ( ec.value(), 5 );
+        BOOST_TEST( ec.category() == sys::system_category() );
+        BOOST_TEST_EQ( &ec.location(), &loc );
+
+        BOOST_TEST_EQ( ec.what(), ec.message() + " [system:5 at " + loc.to_string() + "]" );
+    }
+
+#if defined(BOOST_SYSTEM_HAS_SYSTEM_ERROR)
+
+    {
+        std::error_code ec;
+        sys::error_code ec2( ec );
+
+        BOOST_TEST_EQ( ec2.what(), ec2.message() + " [std:system:0]" );
+    }
+
+    {
+        std::error_code ec( 5, std::generic_category() );
+        sys::error_code ec2( ec );
+
+        BOOST_TEST_EQ( ec2.what(), ec2.message() + " [std:generic:5]" );
+    }
+
+    {
+        std::error_code ec( 5, std::system_category() );
+        sys::error_code ec2( ec );
+
+        BOOST_TEST_EQ( ec2.what(), ec2.message() + " [std:system:5]" );
+    }
+
+#endif
+
+    return boost::report_errors();
+}