Re: [RFC updated PATCH 2/2] Bug Translator 3016 : Error accessing members of anonymous structs / unions

[Prerna Saxena <prerna at linux dot vnet dot ibm dot com>]

Thanks Frank,
I've implemented it on the lines you suggested...
Dwarf errors are also flagged as semantic errors, except that they 
additionally set a flag to indicate their nature.
The catch{} block for semantic errors is also a part of the while loop. 
It re-throws all semantic errors which are NOT due to failure in 
fetching dwarf info, while saves  the last dwarf-based error.
In case no match is found in the master (parent) call of 
translate_components() ,  the saved dwarf error is thrown again.


Frank Ch. Eigler wrote:
> Hi -
>
>   
> > As per your suggestion , I've removed the clog messages and instead 
> > replaced them with  a global (static) string to contain error messages 
> > in case of errors encountered in reading/decoding dwarf information. 
> >     
>
> (Actually, there remain one or two hard-coded clog references in the
> patch, unless I'm misreading.)
>   
Thanks for pointing that out, I removed the clog message...it wasn't 
required.. :-)
> The use of the static error_msg string is unnecessary.  I advised
> having an explicit try {} catch () within the search iterations, so
> that each layer can just throw an exception if something is wrong.
> The parent can catch exceptions and try another branch.  If the search
> is unsuccessful, it can throw a new (or saved/reused) exception of its
> own.  This should also simplify the logic.
>
> - FChE
>   
Pls let me know your comments..

Regards,

--
Prerna Saxena

Linux Technology Centre,
IBM Systems and Technology Lab,
Bangalore, India 

Signed-off-by : Prerna Saxena <prerna@linux.vnet.ibm.com>

Index: systemtap/tapsets.cxx
===================================================================
--- systemtap.orig/tapsets.cxx
+++ systemtap/tapsets.cxx
@@ -1845,9 +1845,33 @@ struct dwflpp
     // Output each sibling's name to 'o'.
     while (dwarf_tag (die) == DW_TAG_member)
       {
-	const char *member = (dwarf_diename_integrate (die) ?: "<anonymous>");
+	const char *member = dwarf_diename_integrate (die) ;
+	
+	if ( member != NULL )
+
+		o << " " << member;
+
+	else
+	    { 
+		Dwarf_Die temp_die = *die; 
+		Dwarf_Attribute temp_attr ;
+		
+		 if (!dwarf_attr_integrate (&temp_die, DW_AT_type, &temp_attr))
+                        {
+                          clog<<"\n Error in obtaining type attribute for "
+			      <<(dwarf_diename(&temp_die)?:"<anonymous>");
+                          return ;
+                        }
+
+                   if ( ! dwarf_formref_die (&temp_attr,&temp_die))
+                        {
+                          clog<<"\n Error in decoding type attribute for "
+			      <<(dwarf_diename(&temp_die)?:"<anonymous>");
+                          return ;
+                        }
+		   print_members(&temp_die,o);
 
-	o << " " << member;
+	    }
 
 	if (dwarf_siblingof (die, &die_mem) != 0)
 	  break;
@@ -2283,7 +2307,12 @@ struct dwflpp
     die = translate_components (&pool, &tail, pc, components,
 				&vardie, &die_mem, &attr_mem);
     if(!die)
-	throw semantic_error("Translation failure");
+	{ 
+	  die = dwarf_formref_die (&attr_mem, &vardie);
+          stringstream alternatives;
+          print_members(die,alternatives); 
+	  throw semantic_error("Translation failure :  \n ALTERNATIVES [ " + alternatives.str() + " ] \n");
+	}
 
     /* Translate the assignment part, either
        x = $foo->bar->baz[NN]
@@ -2352,7 +2381,13 @@ struct dwflpp
     die = translate_components (&pool, &tail, pc, components,
 				vardie, &die_mem, &attr_mem);
     if(!die)
-	throw semantic_error("Translation Failure");
+	{ 
+	  die = dwarf_formref_die (&attr_mem, vardie);
+          stringstream alternatives;
+          print_members(die,alternatives); 
+	  throw semantic_error("Translation failure : \n ALTERNATIVES [ " + alternatives.str() + " ] \n");
+	}
+
 
     /* Translate the assignment part, either
        x = $return->bar->baz[NN]