[Bug lto/53831] Inline virtuals missing in LTO symtab

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53831

--- Comment #11 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-07-03 13:11:59 UTC ---
(In reply to comment #10)
> > if I use -fno-fat-lto-objects I get a maybe more easily to debug linker failure
> 
> I guess that's because in this case archive symtab doesn't reference any
> symbols at all (which is another bug):
>   $ nm libdummy.a 
>   impl.o:
>   00000001 C __gnu_lto_slim
>   00000001 C __gnu_lto_v1
> so linker doesn't get any symbols from impl.o (not even _ZTV1C).

you need to use the LTO aware nm that gcc installs, gcc-nm.  It says

> gcc-nm-4.7 libdummy.a 

impl.o:
00000000 T _ZN1C1fEv
00000000 T _ZN1C1gEv
00000000 W _ZTV1C

> > Or your program is invalid because you have no inline definition where you
> have a use.
> 
> I'm not sure whether inline virtual without definition is valid in C++. But I
> googled a bit before submitting the bug and found no evidence that it's a
> non-standard (and more importantly - non-lto g++ accepts this code
> just fine).

Btw, removing the 'inline' keyword everywhere still reproduces the issue.
That makes the testcase certainly valid.