g++ serious bug in Ubuntu Lucid Lynx

Christian Convey christian.convey@gmail.com
Wed Jun 2 16:16:00 GMT 2010

Are you sure that's a bug in the legalistic sense?  IIRC, C and C++
don't promise any particular memory layout for structs.

On Wed, Jun 2, 2010 at 11:53 AM, David R. Doucette
<ddoucette@kldcompanies.com> wrote:
> We just installed Lucid Lynx a few days ago, and have hit a fatal flaw with
> g++ that has forced us to stop the deployment and roll back the systems we
> could.
> Structures in Lucid are now mapping differently than in the past, so we can
> no longer read our own files! Further, if any files are written by code
> produced by the new g++, they are corrupted.
> The problem is that doubles are now being mapped onto a boundary divisible
> by 8 rather than a boundary divisible by 4, meaning that offsets change and
> structs get bigger.
> I've attached a tar file showing the mapping on Jaunty, Karmic, and Lucid to
> show the change. This is a greatly simplified program that shows the
> problem, but it's happening in all of our C++ programs.
> System is Ubuntu 10.4 Lucid Lynx 64 bit.
> David Doucette

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