Jonathon <[email protected]> writes:
> Thanks Tom for the help. The --db-attach command is very cool :)
np.
> So with the invalid read, it is trying to read an address that is not
> valid. Would you happen to know what the line "16 bytes inside a
> block 24 free'd" means?
I think it's telling you where the chunk of memory became invalid. I'd
have to check the docs for the 16 and 24, but maybe the allocator gave
a 24-byte block and the pointer that is invalid points to 16 of them.
> I am using an std::list. Is it possible the problem is in the list?
> and not my actual code?
Possible? Technically, yes. Exceedingly unlikely.
I (highly) recommend -D_GLIBCXX_DEBUG -D_GLIBCXX_CONCEPT_CHECKS when
using the STL w/ libstdc++.
-tom
> On Tue, Aug 11, 2009 at 9:13 AM, tom fogal<[email protected]> wrote:
> > Jonathon <[email protected]> writes:
> >> I was wondering if it is possible to get valgrind to make an "assert"
> >> so my debugger can catch it when a memory error occurs? I would like
> >> to determine what is causing this memory error and it would be nice
> >> if I could do this.
> >
> > No, but it can do better: suspend the process and automatically start
> > your debugger. Use the --db-attach=yes option.
> >
> >> Also, I am having a hard time deciphering this message, can anyone
> >> please give me insight on what this error means? I've tried Google and
> >> I had no luck :(
> > [snip]
> >> 1. ==20770== Invalid read of size 8
> >> 2. ==20770== at 0x662CBB: PacketPool::removePacket(Packet*)
> >
> > It means a variable, of width 8 (e.g. a double, long on amd64, etc.)
> > is being read from yet is not valid. `Read' probably means it's an
> > rvalue. `Invalid' implies the address is bad. IIUC, memory is invalid
> > by default, marked valid when you assign to it, marked invalid when you
> > delete/free it. There's a bit in the memcheck manual about 'shadow
> > bits' and how they are used to track validity, IIRC.
> >
> > -tom
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