Re: [linux-next:master 5266/5426] arch/x86/kernel/cpu/mcheck/mce.c:884:5: warning: 'order' may be used uninitialized in this function

[Andrey Ryabinin <aryabinin@virtuozzo.com>]

On 12/10/2015 06:05 PM, kbuild test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
> head:   8225f4e85cb03daea14661380745886ce01fd83a
> commit: 0dd08f12cafd7868be55bc10ebcd4ea13880860b [5266/5426] UBSAN: run-time undefined behavior sanity checker
> config: x86_64-randconfig-s5-12102221 (attached as .config)
> reproduce:
>         git checkout 0dd08f12cafd7868be55bc10ebcd4ea13880860b
>         # save the attached .config to linux build tree
>         make ARCH=x86_64 
> 
> Note: it may well be a FALSE warning. FWIW you are at least aware of it now.
> http://gcc.gnu.org/wiki/Better_Uninitialized_Warnings
> 

This is certainly a false positive. 
It seems that UBSAN could make gcc more stupid and increase number of maybe-uninitialized false-positives.


> All warnings (new ones prefixed by >>):
> 
>    arch/x86/kernel/cpu/mcheck/mce.c: In function 'do_machine_check':
>>> arch/x86/kernel/cpu/mcheck/mce.c:884:5: warning: 'order' may be used uninitialized in this function [-Wmaybe-uninitialized]
>      if (order == 1) {
>         ^
>    arch/x86/kernel/cpu/mcheck/mce.c:984:6: note: 'order' was declared here
>      int order;

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