Re: [PATCH v2] transport-helper: enforce atomic in push_refs_with_push

On Tue, Jul 16, 2019 at 09:53:59AM -0700, Junio C Hamano wrote:

I expected that this will eventually happen after Travis CI's default Linux image recently changed from Ubuntu 14.04 to 16.04; explanation in the commit message below.

With that patch issues like this could be caught earlier, while they are only in 'pu' but not yet in 'next'. But do we really want to do that, is that the right tradeoff? Dunno... Adding a dedicated CI job just to check that there are no 'for' loop initial declarations seems kind of excessive, even if it only builds but doesn't run the test suite. And I don't know whether there are any other undesired ("too new") constructs that GCC 4.8 would catch but later compilers quietly accept.

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Subject: [PATCH] travis-ci: build with GCC 4.8 as well

C99 'for' loop initial declaration, i.e. 'for (int i = 0; i < n; i++)', is not allowed in Git's codebase yet, to maintain compatibility with some older compilers.

Our Travis CI builds used to catch 'for' loop initial declarations, because the GETTEXT_POISON job has always built Git with the default 'cc', which in Travis CI's previous default Linux image (based on Ubuntu 14.04 Trusty) is GCC 4.8, and that GCC version errors out on this construct (not only with DEVELOPER=1, but with our default CFLAGS as well). Alas, that's not the case anymore, becase after 14.04's EOL Travis CI's current default Linux image is based on Ubuntu 16.04 Xenial [1] and its default 'cc' is now GCC 5.4, which, just like all later GCC and Clang versions, simply accepts this construct, even if we don't explicitly specify '-std=c99'.

Ideally we would adjust our CFLAGS used with DEVELOPER=1 to catch this undesired construct already when contributors build Git on their own machines. Unfortunately, however, there seems to be no compiler option that would catch only this particular construct without choking on many other things, e.g. while a later compiler with '-std=c90' and/or '-ansi' does catch this construct, it can't build Git because of several screenfulls of other errors.

Add the 'linux-gcc-4.8' job to Travis CI, in order to build Git with GCC 4.8, and thus to timely catch any 'for' loop initial declarations. To catch those it's sufficient to only build Git with GCC 4.8, so don't run the test suite in this job, because 'make test' takes rather long [2], and it's already run five times in other jobs, so we wouldn't get our time's worth.

[1] The Azure Pipelines builds have been using Ubuntu 16.04 images
    from the start, so I belive they never caught 'for' loop initial
    declarations.

[2] On Travis CI 'make test' alone would take about 9 minutes in this
    new job (without running httpd, Subversion, and P4 tests).  For
    comparison, starting the job and building Git with GCC 4.8 takes
    only about 2 minutes.

Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
---
 .travis.yml               |  4 ++++
 ci/run-build-and-tests.sh | 17 +++++++++++++----
 2 files changed, 17 insertions(+), 4 deletions(-)