Re: kgdb's weak symbols vs. gcc 4.1

Tom Rini wrote:
> On Mon, May 22, 2006 at 09:24:32PM +0200, Jan Kiszka wrote:
>
> > Hi,
> >
> > I stumbled over some issue of kgdb in combination with gcc 4.1 since
> > kernel 2.6.16. The background can be found in [1]. It melts down that
> > the default arch-dependent functions in kernel/kgdb.c got compiled in -
> > and immediately optimised out again. The effect is, of course, lethal.
> >
> > As a workaround I added "CFLAGS_kgdb.o += -fno-unit-at-a-time" to
> > kernel/Makefile, but I'm not sure if this is the preferred solution
> > here. Alternatives might be to move all default arch-stubs into a
> > separate object file, thus giving the linker the chance again to handle
> > them, or to use #ifndef KGDB_HAVE_ARCH_xxx constructs.
>
>
> This sounds kind of like a gcc bug.  If you have the message from
> Florian Weimer could you please bounce me a copy?  I'd like to verify
> that the correct solution to this problem is roughly:
> 1) kgdb.h includes weak declarations
> 2) kernel/kgdb.c does not provide any copy of the function
> 3) arch/$ARCH/kernel/kgdb.c may or may not provide the function
> and finally
> 4) There's a way to get the desired behavior out of both gcc-4.1 and
> gcc-3.3 at least.  Thanks!

I think you also need to provide a library of weak functions, it just needs 
to be in a different *.c so gcc doesn't see it and conclude that it can drop 
it.  I.e. the linker needs to see both the real arch version and the weak 
version.

One wonders what gcc would do if the weak module was not empty...
>

--
George Anzinger   george@xxxxxxxxxxxxxxxxxxx
HRT (High-res-timers):  http://sourceforge.net/projects/high-res-timers/


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