Re: pending breakpoints change breakpoint number

[Jim Ingham <jingham at apple dot com>]

Andrew,

Yes, the one symbolic->many actual breakpoints is something I am 
interested in working on.  It is high on my "list of tasks I keep 
trying to get into the next release".  Sadly, it didn't make it into 
the current release, so it will be a little while (certainly not till 
after WWDC in July) before I can get to this.

I still think the notification is necessary, and is a fairly small 
change.  I am sure the Eclipse folks are also going to run into this 
like the Xcode folks did.  And if we also include the address(s) the 
breakpoint resolved to (and maybe the symbol name - which would be 
useful for file:line breakpoints in template functions), then the 
notification will be useful even after we fix the M:N problem.  It 
means that a GUI which displays the addresses of breakpoints as part of 
its breakpoint display can keep these up to date without needing an 
extra round trip to gdb...

I fixed it in our sources so that I only change the breakpoint number 
when we set more than one breakpoint.  That was a simple change since 
you already have the pending breakpoint in create_breakpoints, though 
it is admittedly a bit of a hack.  Still it actually fixes most cases 
and seems to me better than the current state of things.  But this 
isn't nearly as important as the notification.

Jim

On May 5, 2004, at 7:52 AM, Andrew Cagney wrote:

> > Hi, all...
> > I have been looking at the pending breakpoint changes (to merge them 
> > into the Apple gdb).  Overall it is nicer than the future-break 
> > version that we had, so that is great.
> > However, one thing really bugs me about it.  That is that it changes 
> > the breakpoint number out from under me when it manages to resolve 
> > the breakpoint.
> > This is pretty annoying to a human user, since if I want to do 
> > anything to the breakpoint, I have to go find it's number again from 
> > info break.  But it is very bad for a gui that is trying to run gdb 
> > from, say, the MI.  The GUI has to use the breakpoint number to do 
> > things like disable the breakpoint, delete it, etc.  So if the number 
> > switches out from under it, the gui can no longer operate on the 
> > breakpoint.  Very bad...
> > So there are two things that need to be addressed here.
> > First off, if we are going to change the breakpoint number, clearly 
> > need a breakpoint_resolved event/hook/observer thingie that we can 
> > use to tell the GUI that breakpoint 2 resolved to breakpoint 5, and 
> > the GUI needs to change accordingly.  This is pretty easy.  If it 
> > were a gdb_event, the addition to gdb-events.sh would look like:
>
> The breakpoint number changing is a known bug in the current 
> implementation.  It was concluded that fixing it (a non-trivial task) 
> was closely tied to fixing things like M:N breakpoints (one breakpoint 
> with multiple locations) and hence should be made part of that task 
> (painful but working pending breakpoints were considered better than 
> no pending breakpoints).
>
> Seems that the N:M breakpoints have fallen by the wayside.  Interested 
> in working on that?  Daniel can give you a status report of where 
> things are at.
>
> Andrew
--
Jim Ingham                                   jingham@apple.com
Developer Tools
Apple Computer