Re: [Boost-users] Re: Bad adjacency_iterator with -O2, -m64 and gcc 3.2.2 on an opteron

From: Michal Simecek (simecek_at_[hidden])
Date: 2005-04-11 01:26:24

> Michal Simecek wrote:
> 
> 
> > compiling and linking the following program on a opteron with the
> > following command
> > and the operating system red hat 3 (current enterprise server version)
> > 
> >    gcc-3.2.2 -c -I. -I../source -I./boost_1_32_0 -O2 -m64 boosttest.cc
> -o
> > boosttest.o
> >    gcc-3.2.2 -m64 -o boosttest boosttest.o -lstdc++
> > 
> > will cause, that the program runs into an endles loop. I figured out,
> that
> > the
> > pointer in VIter which is compared when comparing VIter and VIterEnd is
> > damaged.
> ..
> >   tie(VIter, VIterEnd) = boost::adjacent_vertices(MyVDescriptor,
> >   MyGraph2);
> > 
> >   while ( VIter != VIterEnd )
> >   {
> >     std::cout << "loop  ..." << std::endl;
> >     ++VIter;
> >   }
> 
> What does "damaged" means? Is it "damaged" at the time of creation. If
> not,
> you should be able to single step in the debugger, and locate the point
> where it's damaged. Or you can set hardware watch point and the memory
> location that's damaged and let gdb/processor find the point that damages
> the variable.

"demaged" means, that it dont looks like a valid address, but this is just
a guess. But a fact is that the value does not change when the iterator gets
increased.
Debugging is  a good idea, but i had the hope to find somebody who did it
already, because its not funny to debug optimized code.
And without optimisation everything works fine.

> 
> Once that one, we might try to investigate further.
> 
> > Is it an optimization bug in the compiler or any mistake I made or a
> > problem in
> > the boost?
> 
> Impossible to tell without more specific details.

Yes, I see what you mean, but it is hard to find more specific
details.

Thanks, Michal

> 
> - Volodya
> 
> 
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