Re: Slow handling of C++ symbol names

[Daniel Jacobowitz <drow at mvista dot com>]

On Thu, Nov 20, 2003 at 11:08:59AM -0500, Andrew Cagney wrote:
> >
> >Have you tried a more recent version of GDB?  This may have been
> >improved.  Definitely some startup time issues were fixed.
> 
> Nothing in the ChangeLogs jumped out.

Well, I remember fixing some startup time issues since then :P  For
instance, the cache shared between minimal and partial symbols should
cut demangling time about in half.

> >Also, the demangler actually comes from GCC, not GDB.
> 
> I don't see GCC being motivated to fix it though :-(
> 
> >  All we can do is
> > try to call it less often.
> 
> Which leads to the question.  Why does GDB demangle symbols?  My 
> simplistic understanding of the code is that GDB only needs the "iw" 
> (a.k.a., demangled string up to  but excluding the lparen and ignoring 
> white space) part of the symbol in the search table (the rest isn't so 
> critical and can be constructed on-demand).

A substantial amount of  demangling is needed to produce the part of
the symbol before the lparen; consider templates.  Also, we need the
full names in the minimal symbol for break 'foo(int)' with quotes to
work.  And there are assumptions of unique symbol names in our
hashing/searching, IIRC.

I'm sure there are tricks we can do to cut down on how early or often
we demangle, but it still seems to be necessary.

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer