Bug#911022: flann breaks hugin autopkgtest: undefined symbol: LZ4_resetStreamHC

[Andreas Metzler]

On 2018-10-14 Jochen Sprickerhof <jspricke at debian.org> wrote:
> * Paul Gevers <elbrus at debian.org> [2018-10-14 21:47]:
>> Source: flann, hugin
>> Control: found -1 flann/1.9.1+dfsg-4
>> Control: found -1 hugin/2018.0.0+dfsg-2
[...]
>> With a recent upload of flann the autopkgtest of hugin fails in testing
>> when that autopkgtest is run with the binary packages of flann from
>> unstable. It passes when run with only packages from testing. In tabular
>> form:
>>                       pass            fail
>> flann                  from testing    1.9.1+dfsg-5
>> hugin                  from testing    2018.0.0+dfsg-2
>> all others             from testing    from testing
>> 
>> I copied some of the output at the bottom of this report.
>> 
>> Currently this regression is contributing to the delay of the migration
>> of flann to testing [1]. Due to the nature of this issue, I filed this
>> bug report against both packages. Can you please investigate the
>> situation and reassign the bug to the right package? If needed, please
>> change the bug's severity.
[...] 

>> Written output to /tmp/tmp.ZePC1LACt6.hugin/pano.pto
>> cpfind: symbol lookup error: cpfind: undefined symbol: LZ4_resetStreamHC
>> autopkgtest [16:37:00]: test simple.pano.test: -----------------------]


> Hi Paul,

> thanks for the report. The new flann version (1.9.1+dfsg-5) doesn't bundle
> lz4 anymore (as per policy and because it broke in Ubuntu, see LP: 1786543.

Hello Jochen,

Just to sum it up some more:

1. flann uses lz4
2. it used to make use of an included lz4 copy and is not doing so
   anymore

The patch changes hugin to link cpfind with
-llz4 -lflann -lflann_cpp (That is `pkg-config --libs flann`)
instead of
-lflann_cpp

I guess flann not only exposes lz4 in its header but also flann-using
packages directly call lz4-functions when using flann functions. Which
would explain why transitive linking to lz4 via fall is not enough.
(Hugin FTBFS).

Is this correct?

Anyway, this change seems to be a ABI break for flann, I guess it will
need to add a
Breaks: hugin (<< fixed-version~)

> I send a pull request to make use of pkg-config in Hugin:

> https://salsa.debian.org/debian-phototools-team/hugin/merge_requests/1

> @Andreas can you release a new Hugin version with this included? If you
> don't have time, I would push a NMU version to delayed/5, if that's ok with
> you.

I will make an upload.

cu Andreas
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