Re: [RFC/dwarf-2] Add support for included files

[Joel Brobecker <brobecker at gnat dot com>]

> Could you try one more thing for me?

Sure!

> As you noticed, the only two functions that dwarf_decode_lines calls
> to actually record the information it gets are
> buildsym.c:start_subfile (via dwarf2_start_subfile) and
> buildsym.c:record_line.  Could you change dwarf_decode_lines to take
> two function pointers (with an accompanying closure pointer) for those
> two functions?  I guess this is an instance of the 'builder' pattern,
> so maybe name it something appropriately suggestive.  Let
> dwarf_decode_lines continue to call dwarf2_start_subfile directly,
> just passing the builder func and closure along with filename and
> dirname.
> 
> Then, instead of duplicating dwarf_decode_lines, have the existing
> call in read_file_scope and the new call you've added just pass
> different function/closures to it.

I was just wondering, before trying that, if we couldn't maybe do
it in a little simpler way, but non-generic way.

Using the approach you suggest (which I like): We need to define a
couple of wrapper functions around start_subfile and record_line
because their profile will not match the profile of our callbacks.
We'll need 3 callbacks per case (3 for psymtabs, 3 for symtabs).
We'll also have to use void* pointers if we want to make the context
generic, which I would prefer to avoid. It's great for heavily reused
code, but is this worth it for this function.

What we could do instead, is:
  . Add a new parameter: struct partial_symtab *pst
  . If this pst is NULL, then scan for symtabs as before
  . If pst is non NULL, then scan for partial symtabs, and do not
    call the 2 buildsym.c functions.

Just for illustration purposes, I tweaked my previous patch. Attached
is a new patch that shows what it would become. I did this because
even if we end up not choosing this solution, it's still a good
intermediate version on which to implement your suggestion.

I verified that the performance impact on GDB was still pretty small.

If you like it, then I'll review, clean it up and properly submit it
for review. Otherwise, I'll send a new version including your
suggestion.

Thanks,
-- 
Joel

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