Re: [xen-unstable-smoke bisection] complete build-arm64-xsm

From: Doug Goldstein <cardoe@cardoe.com>
To: Wei Liu <wei.liu2@citrix.com>, Andrew Cooper <andrew.cooper3@citrix.com>
Cc: xen-devel@lists.xenproject.org,
	Julien Grall <julien.grall@arm.com>,
	Stefano Stabellini <sstabellini@kernel.org>,
	osstest-admin@xenproject.org, Jan Beulich <JBeulich@suse.com>
Subject: Re: [xen-unstable-smoke bisection] complete build-arm64-xsm
Date: Wed, 14 Mar 2018 08:42:32 -0500	[thread overview]
Message-ID: <66849ecf-4f84-a1fc-dfbf-64b5293a7c1d@cardoe.com> (raw)
In-Reply-To: <20180314105447.3tjfpeek535lxtbq@citrix.com>

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On 3/14/18 5:54 AM, Wei Liu wrote:
> On Wed, Mar 14, 2018 at 09:01:10AM +0000, Andrew Cooper wrote:
>> On 14/03/2018 07:59, Jan Beulich wrote:
>>>>>> On 14.03.18 at 03:29, <osstest-admin@xenproject.org> wrote:
>>>> branch xen-unstable-smoke
>>>> xenbranch xen-unstable-smoke
>>>> job build-arm64-xsm
>>>> testid xen-build
>>>>
>>>> Tree: qemuu git://xenbits.xen.org/qemu-xen.git
>>>> Tree: xen git://xenbits.xen.org/xen.git
>>>>
>>>> *** Found and reproduced problem changeset ***
>>>>
>>>>   Bug is in tree:  xen git://xenbits.xen.org/xen.git
>>>>   Bug introduced:  b43501451733193b265de30fd79a764363a2a473
>>>>   Bug not present: eef83fd2af0d4c78afec34c199c977fc97d8a0b3
>>>>   Last fail repro: http://logs.test-lab.xenproject.org/osstest/logs/120707/ 
>>>>
>>>>
>>>>   commit b43501451733193b265de30fd79a764363a2a473
>>>>   Author: Doug Goldstein <cardoe@cardoe.com>
>>>>   Date:   Mon Mar 12 23:06:51 2018 -0500
>>>>   
>>>>       tools: detect appropriate debug optimization level
>>>>       
>>>>       When building debug use -Og as the optimization level if its available,
>>>>       otherwise retain the use of -O0. -Og has been added by GCC to enable all
>>>>       optimizations that to not affect debugging while retaining full
>>>>       debugability.
>>>>       
>>>>       Signed-off-by: Doug Goldstein <cardoe@cardoe.com>
>>>>       Acked-by: Wei Liu <wei.liu2@citrix.com>
>>> Sadly altering optimization levels always has the potential of
>>> triggering issues like this:
>>>
>>> xc_dom_arm.c: In function 'meminit':
>>> xc_dom_arm.c:446:5: error: 'p2m_size' may be used uninitialized in this function [-Werror=maybe-uninitialized]
>>>      for ( pfn = 0; pfn < p2m_size; pfn++ )
>>>      ^
>>> cc1: all warnings being treated as errors
>>> /home/osstest/build.120709.build-arm64-xsm/xen/tools/libxc/../../tools/Rules.mk:230: recipe for target 'xc_dom_arm.o' failed
>>> make[5]: *** [xc_dom_arm.o] Error 1
>>
>> We really should be build testing things at all optimisation levels.  We
>> should be ashamed that -O3 gives build failures in most of our major
>> components.  (This is yet another item on my TODO list which I've not
>> had time to complete.)
> 
> I agree with your opinion in general.
> 
> In this particular case, I think the compiler is to be blamed. p2m_size
> should have been initialised in a previous loop by the time the code
> comes to the place gcc complained.
> 
> Wei.
> 

Agreed. But the compiler used by osstest won't be changing any time soon
to pick up fixes.

What would the ARM maintainers like me to do? Initialize it to 0 at the top?

-- 
Doug Goldstein

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