On Sat, Jun 01, 2019 at 12:41:43AM +0000, brian m. carlson wrote:

On 2019-05-30 at 19:32:41, Johannes Schindelin wrote:

quoted

Hi Gábor,

do you have any idea why Travis is failing like this in the macOS/gcc
job?

quoted

+case "$jobname" in
+brew link gcc@8
Error: No such keg: /usr/local/Cellar/gcc@8
The command "ci/install-dependencies.sh" failed and exited with 1 during .

I usually only look at the Azure Pipelines (which gives me plenty enough
to do, what with pu's individual branches being tested individually), but
couldn't fail to notice that *all* four branches (maint, master, next and
pu) fail in Travis' macOS/gcc job (and only there, the Azure Pipelines are
all green):

https://github.com/git/git/branches/all

What's going on?

The usual: Homebrew desperately tries to be overly clever and helpful,
but ends up being dumb and annoying. :)

I was hoping that this issue will just solve itself, like several
other brew breakages in the past, but apparently it won't...

I'm certainly not an expert on macOS, so I could be getting things wrong
here, but it looks like we don't ever explicitly install the gcc@8
package from Homebrew. It may have happened to be installed
automatically by Travis in the past, but they may have upgraded now that
GCC 9 has been released.

gcc@8 is still installed in the Travis CI macOS image we use, but it
is version 8.2.  It's still perfectly usable, but:

When installing dependencies on macOS, we first explicitly run 'brew
update', which spends over two minutes to update itself and
information about the available packages.  This way it learns about
GCC 8.3, and after that gcc@8 refers to v8.3, and, unfortunately,
'brew' is just too dumb to be able to do anything with the still
installed 8.2 package, and the subsequent 'brew link gcc@8' fails.
But hey, even 'brew uninstall gcc@8' fails with the same error after
that, which is simply unacceptable from a package manager in my book.

I suspect if we want to use GCC 8, we need to explicitly install it by
using "brew install gcc@8", or we can just pick the latest released GCC
by using "brew install gcc" if we like that better. We will still need
to do "brew link gcc" (or "gcc@8"), since I suspect Homebrew won't
auto-link it since macOS provides a gcc binary.

Yeah, installing gcc@8 or gcc works.  Back in 2c8921db2b (travis-ci:
build with the right compiler, 2019-01-17) I opted for simply linking
the already installed gcc@8 package, because GCC is big, installing it
takes time, and the macOS build jobs have always been prone to
exceeding the time limit.  (Note that these packages provide 'gcc-8'
and 'gcc-9' binaries, not 'gcc', and after 'brew install'-ing them we
won't need an additional link step (I'm not sure why linking is
necessary with the gcc@8 package already installed in the Travis CI
image).)

Another possibilities are:

  - Running 'brew link gcc@8' before 'brew update' works:

      https://travis-ci.org/szeder/git/jobs/540027012#L139

  - Not running 'brew update' at all works as well:
  
      https://travis-ci.org/szeder/git/jobs/514960153#L179
  
    However, it's not as simple as removing the 'brew update' command
    from our ci script, because 'brew' is so very helpful that it
    implicitly runs update for us on the next 'brew install' anyway...
    we have to 'export HOMEBREW_NO_AUTO_UPDATE=1' first to disable
    that.

    As an additional benefit, disabling 'brew update' shaves off over
    2mins from the ~4mins currently spent on installing dependencies
    [1].

    I've been running my somewhat customized builds on Travis CI [2]
    without 'brew update' for about a month now, no ill effects yet.
    Initially I was worried that without 'brew update' a subsequent
    'brew install <pkg>' might fail, if the package repositories
    contain only a newer version of 'pkg'.  I haven't seen any such
    issues yet, and my builds can still 'brew install' Git-LFS 2.5.2
    and Perforce 18.1, although their current versions are 2.7.2 and
    19.1, respectively.


[1] And disabling the recently introduced auto cleanup feature saves
    some more time, and installing all dependencies in the macOS
    builds can be done in ~20-30secs:

      https://travis-ci.org/szeder/git/jobs/514960153#L92

[2] https://travis-ci.org/szeder/git-cooking-topics-for-travis-ci/branches