Hangs in GDB auto-complete

Hangs in GDB auto-complete

[Kristoffer Sjöö]

Hi.
After I upgraded my Ubuntu system to Lucid Lynx (10.04), I started to 
notice extremely slow responses from GDB when using auto-complete - from 
a few seconds to several minutes (at which point I usually kill GDB out 
of impatience).

Scanning the Web and the mailing list archives as well as the bug 
tracker I couldn't find anything related and so I'm assuming it's not a 
widespread problem and likely something weird that's arisen in my 
system. Thus I didn't want to file a bug report, but thought I'd ask 
here instead.

It's very irritating, especially when I end up having to kill GDB. It 
mostly occurs when I try to auto-complete using Tab, especially when 
I've misspelled the initial part and there's no match. But it also 
occurs sometimes when I type things like "break 422" while stepping 
through a file.
I've no notion of the inner workings of GDB and no idea what this is all 
due to, but perhaps someone here has some clue? It's really hampering my 
work sometimes and I never saw it prior to my upgrade to 10.04.

Kristoffer

Re: Hangs in GDB auto-complete

[Tom Tromey]

>>>>> "Kristoffer" == Kristoffer Sjöö <krsj@nada.kth.se> writes:

Kristoffer> After I upgraded my Ubuntu system to Lucid Lynx (10.04)

What version of gdb?

Kristoffer> It's very irritating, especially when I end up having to
Kristoffer> kill GDB.

You should be able to C-c out of any completion.
If you can't, then that is a gdb bug.

Kristoffer> I've no notion of the inner workings of GDB and no idea what
Kristoffer> this is all due to, but perhaps someone here has some clue?

We need more details, ideally enough to try to reproduce the problem.
It could be any number of things, depending on the details of what you
are doing.

Tom

Re: Hangs in GDB auto-complete

[Michael Snyder]

Tom Tromey wrote:
>>>>>> "Kristoffer" == Kristoffer Sjöö <krsj@nada.kth.se> writes:
> 
> Kristoffer> After I upgraded my Ubuntu system to Lucid Lynx (10.04)
> 
> What version of gdb?
> 
> Kristoffer> It's very irritating, especially when I end up having to
> Kristoffer> kill GDB.
> 
> You should be able to C-c out of any completion.
> If you can't, then that is a gdb bug.
> 
> Kristoffer> I've no notion of the inner workings of GDB and no idea what
> Kristoffer> this is all due to, but perhaps someone here has some clue?
> 
> We need more details, ideally enough to try to reproduce the problem.
> It could be any number of things, depending on the details of what you
> are doing.

I think I've seen something like this -- on large symbol files with many 
symbols, gdb gets into a tight loop in completion that doesn't seem to 
respond to ^C.  Just speaking from memory ...

Re: Hangs in GDB auto-complete

[Paul Koning]

On Nov 16, 2010, at 12:50 PM, Michael Snyder wrote:

> Tom Tromey wrote:
>>>>>>> "Kristoffer" == Kristoffer Sjöö <krsj@nada.kth.se> writes:
>> Kristoffer> After I upgraded my Ubuntu system to Lucid Lynx (10.04)
>> What version of gdb?
>> Kristoffer> It's very irritating, especially when I end up having to
>> Kristoffer> kill GDB.
>> You should be able to C-c out of any completion.
>> If you can't, then that is a gdb bug.
>> Kristoffer> I've no notion of the inner workings of GDB and no idea what
>> Kristoffer> this is all due to, but perhaps someone here has some clue?
>> We need more details, ideally enough to try to reproduce the problem.
>> It could be any number of things, depending on the details of what you
>> are doing.
> 
> I think I've seen something like this -- on large symbol files with many symbols, gdb gets into a tight loop in completion that doesn't seem to respond to ^C.  Just speaking from memory ...
> 

Yes, that's something I run into every week or two, when I hit tab in the wrong spot.

	paul

Re: Hangs in GDB auto-complete

[Kristoffer Sjöö]

On 2010-11-16 18:20, Tom Tromey wrote:
> Kristoffer>  After I upgraded my Ubuntu system to Lucid Lynx (10.04)
>
> What version of gdb?
>    

gdb --version
GNU gdb (GDB) 7.1-ubuntu

> Kristoffer>  It's very irritating, especially when I end up having to
> Kristoffer>  kill GDB.
>
> You should be able to C-c out of any completion.
> If you can't, then that is a gdb bug.
>    

Well, I can't C-c. I'm stuck in one of these right now, in fact; it's 
been locked up for 2-3 minutes now, at 148 % CPU according to top:
7563 krsj      20   0  184m 169m  67m R  148  8.5   5:55.72 gdb

Oh, wait! My C-c went through after 2 minutes! As I said, they're not 
infinite lockups, but for practical purposes they may as well be sometimes.

This lockup happened when I typed

(gdb) p m_evaluator.m_lastWitness

...which isn't even an auto-complete, but just a symbol lookup. This 
particular one should work, too; it's not a typo. I'll try it again 
without C-c to see if it does find the symbol eventually...

The executable in question is attached while running, not started by 
gdb, but another smaller project I am working on suffers from the same 
problem while being started the usual way.

> Kristoffer>  I've no notion of the inner workings of GDB and no idea what
> Kristoffer>  this is all due to, but perhaps someone here has some clue?
>
> We need more details, ideally enough to try to reproduce the problem.
> It could be any number of things, depending on the details of what you
> are doing.
>    

I'll see if I can find some method in the madness. Pretty sure it's got 
nothing to do with the code I'm debugging but with my system and the way 
gdb is configured somehow. (I haven't deliberately modded gdb in any 
way, I hasten to add.)

There, the print command went through finally:
(gdb) p m_evaluator.m_lastWitness
$111 = {point1 = {x = 0.095000000000000001, y = 0.044999999999999998, z 
= 1}, point2 = {x = 0.095000000000000001, y = 0.044999999999999998, z = 
1.2599999713897705},
   distance = 0.25999997138977049, typeOnA = spatial::WITNESS_FACE, 
typeOnB = spatial::WITNESS_VERTEX, idOnA = 0, idOnB = 4, paramOnA = 0, 
paramOnB = 7.5651897269402635e-306,
   normal = {x = 0, y = 0, z = 1}}

I sure would like to be able to query variables reliably in less than 
three minutes, though...
I'll see what I can do about setting up a repro case.

Kristoffer

Re: Hangs in GDB auto-complete

[Tom Tromey]

>>>>> "Kristoffer" == Kristoffer Sjöö <krsj@nada.kth.se> writes:

Kristoffer> Well, I can't C-c. I'm stuck in one of these right now, in
Kristoffer> fact; it's been locked up for 2-3 minutes now, at 148 % CPU
Kristoffer> according to top:

One thing that might help is if you installed the gdb debuginfo, then
attached a new gdb to the hung gdb to get a stack trace.

Kristoffer> This lockup happened when I typed
Kristoffer> (gdb) p m_evaluator.m_lastWitness
Kristoffer> ...which isn't even an auto-complete, but just a symbol
Kristoffer> lookup.

This sounds like the namespace lookup performance problem.
This was fixed in 7.2.

Tom

Re: Hangs in GDB auto-complete

[Kristoffer Sjöö]

On 2010-11-18 22:31, Tom Tromey wrote:
>>>>>> "Kristoffer" == Kristoffer Sjöö<krsj@nada.kth.se>  writes:
>>>>>>              
> Kristoffer>  Well, I can't C-c. I'm stuck in one of these right now, in
> Kristoffer>  fact; it's been locked up for 2-3 minutes now, at 148 % CPU
> Kristoffer>  according to top:
>
> One thing that might help is if you installed the gdb debuginfo, then
> attached a new gdb to the hung gdb to get a stack trace.
>
> Kristoffer>  This lockup happened when I typed
> Kristoffer>  (gdb) p m_evaluator.m_lastWitness
> Kristoffer>  ...which isn't even an auto-complete, but just a symbol
> Kristoffer>  lookup.
>
> This sounds like the namespace lookup performance problem.
> This was fixed in 7.2.
>    

Yeah, 7.2 is like a whole new debugger! (Or, like the older versions 
where I didn't see this problem). Anyway, thanks!

Kristoffer