[Bug c++/60566] [4.9 Regression] r208573 miscompiles kdelibs

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60566

--- Comment #7 from Jason Merrill <jason at gcc dot gnu.org> ---
(In reply to Markus Trippelsdorf from comment #4)
> part.ii is part of a library called libkparts.so.4.12.3.
> When I compile part.cpp with a compiler before r208573 and link the 
> library (all other objects files for the lib are unchanged) and then install
> the library to my system /usr/lib folder, Okular starts and works fine.
> 
> If I compile part.cpp with a compiler _after_ r208573 and link the 
> library and install it, Okular shows a popup "Unable to find the Okular 
> component".

Just to be clear, you've tested specifically 208572 vs 208573?  Recompiling
just that one file?

> Looking at the library, the only difference are four additional
> symbols in the good version:
> 
> _ZThn16_N6KParts13ReadWritePartD0Ev
> _ZThn16_N6KParts13ReadWritePartD1Ev
> _ZTv0_n24_N6KParts13ReadWritePartD0Ev
> _ZTv0_n24_N6KParts13ReadWritePartD1Ev

These are thunks to the destructor, which are unneeded if the (constructor)
vtable doesn't refer to them anymore.

(In reply to Jakub Jelinek from comment #5)
> So, can you perhaps with the part_good.s put a breakpoint on the 2 dtors and
> 4 thunks to those, and see if they are ever called during the startup of
> Okular?

Or with part_bad, put a breakpoint on __cxa_pure_virtual?