Re: C++ binary compatibility

[Sverre Froyen <sverre%viewmark.com@localhost>]

On Thursday 19 June 2008, Mark Davies wrote:
> On Thursday 19 June 2008 19:24:13 James Chacon wrote:
> > Was there ever a decision here? Leaving the current libstdc++ at major
> > 6 when that isn't binary compatible with older copies from 4.0 seems
> > really wrong.
>
> Its PR 38804 and its on the "high priority" list to be looked at before 5.0
> but I'm not aware of anyone actively looking at it.  (I'm happy to help
> where I can but don't don't have any ideas where to start).
>
> > Any reason not to just bump it's version?
>
> Presumably people would like to understand what changed before making that
> decision.

I made an attempt to debug the issue before finally recompiling the kde 
libraries.

It looks like an instance of std::basic_istream gets clobbered.  I tried to 
watch the address location but without hardware watchpoint support in gdb it 
takes too long (code executes at least 100,000 slower when using 
watchpoints).  My suspicion is that the kde libraries has the sizeof some 
structure compiled-in and that the new libstdc somehow has a different size 
for that structure.

Sverre