Re: symtab/1379: GDB doesn't scope nested functions properly

[Daniel Jacobowitz <drow at mvista dot com>]

The following reply was made to PR symtab/1379; it has been noted by GNATS.

From: Daniel Jacobowitz <drow@mvista.com>
To: jingham@apple.com
Cc: gdb-gnats@sources.redhat.com
Subject: Re: symtab/1379: GDB doesn't scope nested functions properly
Date: Tue, 16 Sep 2003 22:44:18 -0400

 On Tue, Sep 16, 2003 at 06:32:52PM -0000, jingham@apple.com wrote:
 > 
 > >Number:         1379
 > >Category:       symtab
 > >Synopsis:       GDB doesn't scope nested functions properly
 > >Confidential:   no
 > >Severity:       serious
 > >Priority:       medium
 > >Responsible:    unassigned
 > >State:          open
 > >Class:          change-request
 > >Submitter-Id:   net
 > >Arrival-Date:   Tue Sep 16 18:38:00 UTC 2003
 > >Closed-Date:
 > >Last-Modified:
 > >Originator:     jingham@apple.com
 > >Release:        Top of tree as of 09-16-2003
 > >Organization:
 > >Environment:
 > Gnu Linux
 > >Description:
 > Compile the file attached to the report for PR 1195.  You will have to use -gstabs+, because of 1195, you won't be able to see subproc at all with Dwarf.
 > 
 > Then break in main and step into nested and from there into subproc.  
 > 
 > Now try to do:
 > 
 > (gdb) print w
 > No symbol "w" in current context.
 > 
 > That is wrong, "w" is in fact visible to subproc.  If you want to test this, change 
 > 
 > int t = z + 1;
 > 
 > to 
 > 
 > int t = z + w + 1
 > 
 > and this will compile fine...
 > 
 > Fixing this will be a bit of a bear, since you are going to have to scope the nested function - into the correct place in the block structure of its main program.  Stabs doesn't really tell you where the nested function is defined, but once you noticed that it was nested (stabs does tell you this) you could go to the line table for the function, find the first line, then go to the nesting function, find where that line number is in its block structure, and insert the nested function there.  Yecch...
 > 
 > Dwarf2 actually records the nested function in the correct place in the blocks already.  But gdb is going to have to start noticing this at all before it can handle the scoping problem.
 
 I've got some plans (for inline functions) that might end up fixing
 this for DWARF2.  But I really don't like the idea of this sort of hack
 in stabs.  I spent a while making nested classes and namespaces work in
 stabs, but I'm not even planning to submit it; it's too gross, and
 there's too much guessing involved.  Extend stabs to report it
 explicitly if you want it supported.  Or switch to DWARF2.
 
 My two cents, for whatever they're worth, which is probably nothing.
 
 -- 
 Daniel Jacobowitz
 MontaVista Software                         Debian GNU/Linux Developer