Re: [PATCH] /dev/mem gcc weak function workaround

David Miller
2008-04-30T04:28:43Z

From: Venki Pallipadi <venkatesh.pallipadi@intel.com>
Date: Tue, 29 Apr 2008 18:31:09 -0700

> Some flavors of gcc 4.1.0 and 4.1.1 seems to have trouble understanding
> weak function definitions. Calls to function from the same file where it is
> defined as weak _may_ get inlined, even when there is a non-weak definition of
> the function elsewhere. I tried using attribute 'noinline' which does not
> seem to help either.
>
> One workaround for this is to have weak functions defined in different
> file as below. Other possible way is to not use weak functions and go back
> to ifdef logic.
>
> There are few other usages in kernel that seem to depend on weak (and noinline)
> working correctly, which can also potentially break and needs such workarounds.
> Example -
> mach_reboot_fixups() in arch/x86/kernel/reboot.c is one such call which
> is getting inlined with a flavor of gcc 4.1.1.
>
> Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
> Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>

This sounds like a bug. And if gcc does multi-file compilation it
can in theory do the same mistake even if you move it to another
file.

We need something more bulletproof here.

Also, we have a macro for marking things weak "__weak" which should
be used here.