Re: [RFA] Avoid recursivly defined user functions.

[Don Howard <dhoward at redhat dot com>]

On Thu, 4 Apr 2002, Andreas Schwab wrote:

> Michael Snyder <msnyder@redhat.com> writes:
> 
> |> Paul Hilfinger wrote:
> |> > 
> |> > > Executing a recursively defined user function results in a core-dump from
> |> > > gdb:
> |> > 
> |> > ...
> |> > 
> |> > > The following patch catches recursive user function definitions and
> |> > > disallowes them:
> |> > 
> |> > Is the segmentation fault the result of stack overflow? 
> |> 
> |> Yes it is.
> |> 
> |> > If so, I
> |> > point out that there is an 'if' statement, so recursive commands are
> |> > not necessarily wrong, are they?
> |> 
> |> No they're not.  So it's a judgement call.  Is it more important
> |> to allow recursive macros, or to prevent GDB from dumping core?
> |> We're basically running an interpreter here...
> |> 
> |> I guess one thing we could do would be to impose an arbitrary
> |> (possibly user-settable) stack depth limit.  That's more work, 
> |> of course...
> 
> The simple minded check in Don's patch won't catch many cases of infinite
> recursion anyway (mutual recursion, command invocation with arguments).
> 

I think I can detect mutual recursion by walking through the body of each
user-defined command (recursivly).  This amounts to static recursion 
detection. 

I think I could track simple recursion depth at runtime.

I don't see how to track mutual recursion depth at runtime.  Maybe do the
static recursion detection and recursivly flag user-defined commands in
the body?



Can you explain what you mean by "command invocation with arguments"?



-- 
dhoward@redhat.com
gdb engineering