[Bug driver/42690] Undefined reference errors with -flto -fuse-linker-plugin

[davek at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42690

--- Comment #21 from Dave Korn <davek at gcc dot gnu.org> 2010-11-20 20:52:38 UTC ---
(In reply to comment #20)
> If we have to pass libgcc archive in GCC driver, what happens to
> random archives on command line? Will LTO ignore them? It sounds
> like a bad idea. I think the fix should be in linker, not in GCC
> driver.

  Link-time optimisations can only generate new undefined references to
functions that GCC knows how to optimise as builtins, so I think this can only
happen with libgcc and libc references.  In the case of user code and
libraries, there should always be undefined references in the LTO symtabs to
the required functions.