RFC: Generating per-function DWARF line number sections

[nick clifton]

Hi Cary,

> If we have a .debug_line.dwo section, readelf will treat that as a
> fragment, and will not parse the section correctly. We end up with a
> divide-by-zero error when trying to dump the section.

OK I can add a test for .debug_line.dwo and not treat it as a debug_line 
fragement.

> I think we need a better way of identifying fragments of a debug
> sections. What if someone has a function named "dwo"?

Under normal circumstances the fix proposed above will still work 
because gas will create a debug line fragment section called 
.debug_line.text.dwo.  (Assuming that dwo() was compiled with function 
sectioning enabled).

To really muck things up the programmer would have to provide a section 
attribute to the dwo() function as well.  Ie:

void dwo (void) __attribute__((section("dwo"));
void dwo (void) { ; }

And then compile it without function sectioning enabled but with 
--gdwarf-sections enabled.  Which seems pretty unlikely to me.

Cheers
   Nick