[RFC] improving the DWARF information emitted for Ada

[Nicolas Setton]

> Any properly written dwarf reader will ignore attributes it doesn't  
> understand, and hence in theory there should be no need for a - 
> gdwarf-2+ option.  You can just emit the new info by default and  
> everything should work.

The problem is that the switch will also change what is contained in  
the DW_AT_name attributes. For example what is today written as  
"hello__my_array_type" will become "hello.my_array_type". Previously  
we were using double underscores as component separator, and we would  
like to use dots instead.

Right now, external tools (such as gdb, [lib]addr2line, etc) which  
read dwarf-2 for Ada need to have "demangling" functions to transform  
the contents of DW_AT_name into user-friendly strings. We want to  
allow them to get rid of these Ada-specific demanglers, but in the  
meantime we don't want the existing demanglers to choke on unexpected  
contents of DW_AT_name.

> If you are proposing -gdwarf-2+ because you want to have support  
> for both the old and new Ada debug info, then I think that is a  
> misuse of the debug+ convention.  You aren't really adding  
> extensions.  You are just changing from stabs hacks to proper dwarf  
> info.  Also, having the -gdwarf-2+ option may confuse people into  
> thinking that they need it for C++ (which is where the + originally  
> came from).

Understood.

> Not having both means that gdb patches need to get installed first,  
> then the gcc patches, and then you document that gcc version X  
> requires gdb version Y.

I'll check with the gdb-Ada experts what it takes exactly to support  
this.

> Ordinarily this shouldn't be a problem, but I realize that  
> historically gdb support for Ada hasn't been as good as it should  
> be. If we really need both old and new formats, I'd suggest a -f  
> option first, maybe something like -fada-stabs-encodings to get the  
> old format.

OK, no problem for using -fada-stabs-encodings.

Thank you for your comments!

Nicolas