Re: Building Xen 4.14 on Debian Bullseye (WAS Re: Xen compile error)

[Bertrand Marquis <Bertrand.Marquis@xxxxxxx>]

Hi,

> On 9 Oct 2020, at 22:14, Hans van Kranenburg <hans@xxxxxxxxxxx> wrote:
> 
> On 10/9/20 7:40 PM, Julien Grall wrote:
>> Hi,
>> 
>> Thank you for the report.
>> 
>> On 08/10/2020 13:28, ba1020@xxxxxxxxxxxxx wrote:
>>> i try to compile the lates Release 4.14.0 and get stuck here
>>> 
>> In general, I would suggest to use the branch stable-4.14 or 
>> staging-4.14 as we may have fixed some bugs which unfortunately slipped 
>> in the release.
>> 
>> However, for your situation, this would have unfortunately not helped 
>> because the commit d25cc3ec93eb "libxl: workaround gcc 10.2 
>> maybe-uninitialized warning" is not present.
>> 
>> I know that Debian is looking to get Xen 4.14 build with the GCC 10. I 
>> have CCed Ian and Hans who may be able to assist you if you encounter 
>> more bug.
> 
> For Debian, we need to get it to build on a couple of archs. We're
> currently trying to get over this hurdle.
> 
> https://buildd.debian.org/status/package.php?p=xen&suite=experimental
> 
> You need at least these:
> 
> * d25cc3ec93eb ("libxl: workaround gcc 10.2 maybe-uninitialized warning")
> * fff1b7f50e75 ("libxl: fix -Werror=stringop-truncation in
> libxl__prepare_sockaddr_un")
> * 5d45ecabe3c0 ("xen/arm64: force gcc 10+ to always inline generic
> atomics helpers")
> 
> There's also a failure in tools/xenpmd [armhf], which is caused by a
> compiler bug, we chose to unblock it by putting in a temporary
> workaround for now, waiting for what upstream will do about it (or while
> waiting for fix in gcc):
> 
> https://salsa.debian.org/xen-team/debian-xen/-/commit/bb84bb24b55b7906c8dadd736ae1ee0ac22b1e12
> -> "tools/xenpmd: work around gcc 10 bug for xenpmd.c", commit id might
> be lost because of heavy rebasing.

I also came into this one on friday.

I will push a patch today or tomorrow to fix it on xen-devel and we should 
backport it after. 

> 
>> In regard to upstream, I think we want to get 4.14 building out-of-box 
>> with GCC 10 so distros can easily adopt it.
> 
> The three ones mentioned above are definitely backport candidates for
> 4.14 already.

We need to backport those to 4.14 definitely.
Yocto is also using gcc10 so i can also use it to test those.

Regards
Bertrand 

> 
>> I will send an e-mail to request a backport for the commit d25cc3ec93eb 
>> "libxl: workaround gcc 10.2 maybe-uninitialized warning".
>> 
>> Best regards,
>> 
>>> 
>>> 
>>> libxlu_pci.c: In function ‘xlu_pci_parse_bdf’:
>>> libxlu_pci.c:32:18: error: ‘func’ may be used uninitialized in this 
>>> function [-Werror=maybe-uninitialized]
>>>    32 |     pcidev->func = func;
>>>       |     ~~~~~~~~~~~~~^~~~~~
>>> libxlu_pci.c:51:29: note: ‘func’ was declared here
>>>    51 |     unsigned dom, bus, dev, func, vslot = 0;
>>>       |                             ^~~~
>>> libxlu_pci.c:31:17: error: ‘dev’ may be used uninitialized in this function 
>>> [-Werror=maybe-uninitialized]
>>>    31 |     pcidev->dev = dev;
>>>       |     ~~~~~~~~~~~~^~~~~
>>> libxlu_pci.c:51:24: note: ‘dev’ was declared here
>>>    51 |     unsigned dom, bus, dev, func, vslot = 0;
>>>       |                        ^~~
>>> libxlu_pci.c:30:17: error: ‘bus’ may be used uninitialized in this function 
>>> [-Werror=maybe-uninitialized]
>>>    30 |     pcidev->bus = bus;
>>>       |     ~~~~~~~~~~~~^~~~~
>>> libxlu_pci.c:51:19: note: ‘bus’ was declared here
>>>    51 |     unsigned dom, bus, dev, func, vslot = 0;
>>>       |                   ^~~
>>> libxlu_pci.c:29:20: error: ‘dom’ may be used uninitialized in this function 
>>> [-Werror=maybe-uninitialized]
>>>    29 |     pcidev->domain = domain;
>>>       |     ~~~~~~~~~~~~~~~^~~~~~~~
>>> libxlu_pci.c:51:14: note: ‘dom’ was declared here
>>>    51 |     unsigned dom, bus, dev, func, vslot = 0;
>>>       |              ^~~
>>> cc1: all warnings being treated as errors
>>> make[5]: *** [/home/adminjs/xen/tools/libxl/../../tools/Rules.mk:216: 
>>> libxlu_pci.o] Error 1
>>> make[5]: *** Waiting for unfinished jobs....
>>> make[5]: Leaving directory '/home/adminjs/xen/tools/libxl'
>>> make[4]: *** [/home/adminjs/xen/tools/../tools/Rules.mk:240: 
>>> subdir-install-libxl] Error 2
>>> make[4]: Leaving directory '/home/adminjs/xen/tools'
>>> make[3]: *** [/home/adminjs/xen/tools/../tools/Rules.mk:235: 
>>> subdirs-install] Error 2
>>> make[3]: Leaving directory '/home/adminjs/xen/tools'
>>> make[2]: *** [Makefile:72: install] Error 2
>>> make[2]: Leaving directory '/home/adminjs/xen/tools'
>>> make[1]: *** [Makefile:134: install-tools] Error 2
>>> make[1]: Leaving directory '/home/adminjs/xen'
>>> make: *** [Makefile:170: world] Error 2
> 
> Have fun,
> Hans