[Boost-gil] Multi-compiler testing on CircleCI (and channel bug)

Subject: [Boost-gil] Multi-compiler testing on CircleCI (and channel bug)
From: Mateusz Loskot (mateusz_at_[hidden])
Date: 2018-04-06 09:18:23

Hi,

I decided to finally add the CircleCI to our palette of CI-s.
There, I've configured builds with *all* GCC and clang
versions I managed to find reliable Docker images [1] for.

That is:

GCC 4.7, 4.8, 4.9
GCC 5.1, 5.2, 5.3, 5.4, 5.5
GCC 6.1, 6.2, 6.3, 6.4
GCC 7.1, 7.2, 7.3
clang 3.9, 4.0, 5.0

All compile with
-std=c++11
variant=debug
variant=release (ie. <optimization>speed)

(For now, only core tests are enabled, extension tests are disabled.)

Although it may seem unnecessary or superfluous, I decided
to test wide range of compilers after I noticed some versions reproduce
the channel [2] tests are failing for some versions and I couldn't see
the pattern.
So, I suggest we keep testing against range of GCC/clang versions,
at least until all CI the builds become perfectly and constantly green :)

To summary, from tests against 15+ compilers, the channel failures
occur only for just two:

- CircleCI with clang 5.0.1 only (see red build job in [3] workflow)
- Travis CI with GCC 5.4.1 (see [2])
- my local Linux with GCC 5.4.0 and clang 5.0 (see comments and screens in [2])

Question is, are we indeed suffering from an extremely capricious UB
or are we hitting some sort of compiler deficiency.

Just to remind, theres is also the checksum [4] tests failures
which I can only reproduce with VS2017 x64

[1] https://github.com/boostorg/gil/blob/develop/.circleci/config.yml#L15-L74
[2] https://github.com/boostorg/gil/issues/51
[3] https://circleci.com/workflow-run/aa52b030-48fa-42eb-bf0e-473b5ee7d96e
[4] https://github.com/boostorg/gil/issues/49

Best regards,
-- 
Mateusz Loskot, http://mateusz.loskot.net