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From:Björn Persson Date:August 18 2005 10:50am
Subject:Re: Crashes and memory corruption
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onsdagen den 17 augusti 2005 18:46 skrev Warren Young:
> Björn Persson wrote:
> > I had problems earlier that seemed to be caused by dangling pointers, and
> > the documentation wasn't very clear on which methods return copies of
> > data and which return pointers,
>
> So send a patch.  The documentation doesn't fix itself.

I'm pretty sure you don't want any patches from me until I actually know 
something that isn't documented. :-)

> > So a Result object has no pointers into the Query object then?
>
> A simple grep answers this question.  (For the impatient, the answer is,
> "no".)
>
> > But I have to
> > keep the Result until I'm done with all Row and ColData objects, don't I?
>
> Probably not.  For example, Result::at() plainly returns Rows by value.
>   If you get a Row object, and are then done retrieving results, you can
> reuse the Result object.
>
> ColData objects, similarly, are returned by value from Row objects.

Interesting. The question is then: What caused the problems I had earlier, and 
why did they go away when I stopped returning Results and Rows from 
functions? Maybe that was the same bug that's causing my current problem. In 
that case it's not a new bug in GCC 4 for example, as I had GCC 3.4 then.

> You're in a better position to debug this than I am...a live program
> yields more info than the backtrace of a dead one.

Yes, but I lack the necessary experience. I was hoping someone who's familiar 
with the internals of MySQL++ would be able to help me find the problem, or 
that others would have the same problem and know more about it.

> But the fact that 
> the program bombs while trying to do some kind of allocation suggests
> that the heap may already be scragged.  You may be viewing secondary
> damage.

That's very probable, especially with those alerts from GlibC taken into 
account.

> Try running your program under valgrind, or your favorite memory debugger.

I'm afraid I don't have a favorite memory debugger as I've never used one. 
I've heard mentions of Valgrind. I'll see when I can find the time to try it.

Björn Persson
Thread
Crashes and memory corruptionBjörn Persson16 Aug
  • Re: Crashes and memory corruptionWarren Young16 Aug
    • Re: Crashes and memory corruptionBjörn Persson17 Aug
      • Re: Crashes and memory corruptionWarren Young17 Aug
        • Re: Crashes and memory corruptionBjörn Persson18 Aug
          • Re: Crashes and memory corruptionThomas Werth18 Aug
          • Re: Crashes and memory corruptionWarren Young18 Aug
        • Re: Crashes and memory corruptionBjörn Persson25 Nov
          • Re: Crashes and memory corruptionWarren Young15 Dec
            • Re: Crashes and memory corruptionBjörn Persson15 Dec
Re: Crashes and memory corruptionJan Busch20 Dec
  • Re: Crashes and memory corruptionChris Frey20 Dec
Re: Crashes and memory corruptionJan Busch21 Dec