Messages in this thread | | | Date | Fri, 2 May 2008 00:56:33 +0300 | From | Adrian Bunk <> | Subject | huge gcc 4.1.{0,1} __weak problem |
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On Wed, Apr 30, 2008 at 05:49:46AM -0700, Pallipadi, Venkatesh wrote: > > >-----Original Message----- From: David Miller > >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. > > > > The references here > http://gcc.gnu.org/ml/gcc-bugs/2006-05/msg02801.html > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27781 > > seem to suggest that the bug is only with weak definition in the same > file. > So, having them in a different file should be good enough workaround > here. >...
A workaround here is the wrong solution since this isn't the only place that suffers from this issue.
We currently give a #warning for 4.1.0. But not for 4.1.1. (Accordingto the bug >= 4.1.2 is fixed.)
And a #warning is not enough.
The huge problem is that "empty __weak function in the same file and non-weak arch function" has recently become a common pattern with several new usages added during this merge window alone.
And the breakages can be very subtle runtime breakages.
I see only the following choices: - remove __weak and replace all current usages - move all __weak functions into own files, and ensure that also happens for future usages - #error for gcc 4.1.{0,1}
> Thanks, > Venki
cu Adrian
--
"Is there not promise of rain?" Ling Tan asked suddenly out of the darkness. There had been need of rain for many days. "Only a promise," Lao Er said. Pearl S. Buck - Dragon Seed
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