Implemented support for custom to_string overloads for converting boost::error_info objects to string by the boost::diagnostic_information function.

[SVN r50507]

example/example_io.cpp

@@ -19,6 +19,7 @@
 #include <errno.h>
 #include <string>
 #include <iostream>
+#include <sstream>
 
 typedef boost::error_info<struct tag_errno,int> errno_info;
 typedef boost::error_info<struct tag_file_stream,boost::weak_ptr<FILE> > file_stream_info;
@@ -28,6 +29,15 @@ typedef boost::error_info<struct tag_file_name_src,std::string> file_name_src_in
 typedef boost::error_info<struct tag_file_name_dst,std::string> file_name_dst_info; //The destination file name of a failed copy operation.
 typedef boost::error_info<struct tag_function,std::string> function_info; //The name of the C function which reported the failure.
 
+std::string
+to_string( errno_info const & e )
+    {
+    int en=e.value();
+    std::ostringstream s;
+    s << en << ", OS says \"" << strerror(en) << "\"";
+    return s.str();
+    }
+
 char const data[] = "example";
 size_t const data_size = sizeof(data);
 

include/boost/exception/info.hpp

@@ -15,6 +15,14 @@
 namespace
 boost
     {
+    template <class Tag,class T>
+    inline
+    typename enable_if<has_to_string<T>,std::string>::type
+    to_string( error_info<Tag,T> const & x )
+        {
+        return to_string(x.value());
+        }
+
     template <class Tag,class T>
     inline
     error_info<Tag,T>::
@@ -45,7 +53,7 @@ boost
     error_info<Tag,T>::
     value_as_string() const
         {
-        return to_string_stub(value_);
+        return to_string_stub(*this);
         }
 
     namespace

test/diagnostic_information_test.cpp

@@ -9,10 +9,21 @@
 #include <boost/detail/workaround.hpp>
 
 #if BOOST_WORKAROUND(__CODEGEARC__, BOOST_TESTED_AT(0x610))
-struct test_tag {};
+struct test_tag1 {};
+struct test_tag2 {};
 #endif
 
-typedef boost::error_info<struct test_tag,int> tag_int;
+typedef boost::error_info<struct test_tag1,int> tagged_int1;
+typedef boost::error_info<struct test_tag2,int> tagged_int2;
+
+std::string
+to_string( tagged_int2 const & x )
+    {
+    if( x.value()==42 )
+        return "fourty-two";
+    else
+        return "bad value";
+    }
 
 struct
 error1:
@@ -38,19 +49,30 @@ main()
     using namespace boost;
     try
         {
-        error1 x; x << tag_int(42);
+        error1 x; x << tagged_int1(42) << tagged_int2(42);
         BOOST_TEST(x.what()==std::string("error1"));
         throw x;
         }
     catch(
     boost::exception & x )
         {
-        std::string di=boost::diagnostic_information(x);
+        std::string di1=boost::diagnostic_information(x);
+        x << tagged_int1(2) << tagged_int2(2);
+        std::string di2 = diagnostic_information(x);
 #ifndef BOOST_NO_RTTI
-        BOOST_TEST(di.find("type:")!=std::string::npos);
+        BOOST_TEST(di1.find("type:")!=std::string::npos);
-        BOOST_TEST(di.find("error1")!=std::string::npos);
+        BOOST_TEST(di1.find("error1")!=std::string::npos);
 #endif
-        BOOST_TEST(di.find("test_tag")!=std::string::npos);
+        BOOST_TEST(di1.find("test_tag1")!=std::string::npos);
+        BOOST_TEST(di1.find("test_tag2")!=std::string::npos);
+        BOOST_TEST(di1.find("fourty-two")!=std::string::npos);
+#ifndef BOOST_NO_RTTI
+        BOOST_TEST(di2.find("type:")!=std::string::npos);
+        BOOST_TEST(di2.find("error1")!=std::string::npos);
+#endif
+        BOOST_TEST(di2.find("test_tag1")!=std::string::npos);
+        BOOST_TEST(di2.find("test_tag2")!=std::string::npos);
+        BOOST_TEST(di2.find("bad value")!=std::string::npos);
         }
     catch(
     ... )
@@ -60,18 +82,22 @@ main()
     try
         {
         error2 x;
-        x << tag_int(1);
+        x << tagged_int1(42) << tagged_int2(42);
         throw x;
         }
     catch(
     boost::exception & x )
         {
-        std::string w1 = diagnostic_information(x);
+        std::string di1 = diagnostic_information(x);
-        x << tag_int(2);
+        x << tagged_int1(2) << tagged_int2(2);
-        std::string w2 = diagnostic_information(x);
+        std::string di2 = diagnostic_information(x);
-        BOOST_TEST( w1!=w2 );
+        BOOST_TEST( di1!=di2 );
-        BOOST_TEST(w1.find("test_tag")!=std::string::npos);
+        BOOST_TEST(di1.find("test_tag1")!=std::string::npos);
-        BOOST_TEST(w2.find("test_tag")!=std::string::npos);
+        BOOST_TEST(di1.find("test_tag2")!=std::string::npos);
+        BOOST_TEST(di1.find("fourty-two")!=std::string::npos);
+        BOOST_TEST(di2.find("test_tag1")!=std::string::npos);
+        BOOST_TEST(di2.find("test_tag2")!=std::string::npos);
+        BOOST_TEST(di2.find("bad value")!=std::string::npos);
         }
     catch(
     ... )