From mboxrd@z Thu Jan  1 00:00:00 1970
From: dan@cgsoftware.com (Daniel Berlin+list.gcc)
To: Bruno Haible <haible@ilog.fr>
Cc: gcc@gcc.gnu.org
Subject: Re: tail call optimization vs. debugging
Date: Fri, 24 Mar 2000 14:03:00 -0000
Message-id: <r9d0xby9.fsf@dan.resnet.rochester.edu>
References: <200003242038.VAA10143@halles.ilog.fr>
X-SW-Source: 2000-03/msg00657.html

Bruno Haible <haible@ilog.fr> writes:


> For each optimized tail call, in the debugger, there is a stack
>frame missing.
Given, AFAIK.

> Example:
>          A () { B (); }
>          B () { C (); }
>          C () { D (); ... }
> Here gdb will only display the stack frames of A and D. That is, the tail
> call elimination makes debugging very hard.

Maybe, i don't know yet.
> 
> Many GNU programs are compiled with "-O2 -g" by default, which has been
> up to now a good compromise between speed and ease of debugging.
> 
Sure.
> May I suggest:
> 
> 1. that tail call elimination be disabled/enabled by a particular command
>    line option,

Not my call.
> 
> 2. that this command line option be "-fomit-frame-pointer", which is the
>    other optimization which makes debugging impossible. Since -O2 does
>    not imply "-fomit-frame-pointer", "-O2 -g" would continue to produce
>    reasonably debuggable code.
Here's where i have a problem.
-fomit-frame-pointer does not make code undebuggable.
In the past it did have trouble, but it's had frame pointerless
debugging for over a year now, i believe.
When is the last time you tried to debug code with
-fomit-frame-pointer on?

--Dan

> 
> Bruno