On 11/3/18, Changbin Du <changbin...@gmail.com> wrote: > On Fri, Nov 02, 2018 at 04:56:58PM +0100, Arnd Bergmann wrote: >> When CONFIG_CC_OPTIMIZE_FOR_DEBUGGING is set, we get countless warnings >> like >> >> In function 'check_copy_size', >> inlined from 'copy_from_user' at include/linux/uaccess.h:146:6, >> inlined from '__copy_siginfo_from_user' at kernel/signal.c:3032:6: >> include/linux/thread_info.h:147:4: error: call to '__bad_copy_to' declared >> with attribute error: copy destination size is too small >> >> It seems that constant propagation doesn't work well enough to make >> this code reliable, so turn it off for that configuration. >> > This is caused by __compiletime_warning() and fixed by below change > already. Could you try the latest kbuild tree? > > --- a/include/linux/compiler-gcc.h > +++ b/include/linux/compiler-gcc.h > @@ -86,8 +86,10 @@ > #define __compiletime_object_size(obj) __builtin_object_size(obj, 0) > > #ifndef __CHECKER__ > +#ifndef CONFIG_CC_OPTIMIZE_FOR_DEBUGGING > #define __compiletime_warning(message) __attribute__((warning(message))) > #define __compiletime_error(message) __attribute__((error(message))) > +#endif
Right, that works as well, but my version is a bit less invasive as it only disables the __compiletime_error in the one file that introduced the regression, and not all of them. I have built hundreds of randconfig builds and found no other problem with __compiletime_error(), though I did find a bunch of (correct) section mismatch warnings and false-positive -Wformat-overflow= warnings with CONFIG_CC_OPTIMIZE_FOR_DEBUGGING (patches pending). I also got some link errors for which I already posted patches. Arnd