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

[Hans van Kranenburg <hans@xxxxxxxxxxx>]

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.

> 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.

> 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