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Travis persists ccache but does not use ccache #9556
Description
Description
In principle, ccache could dramatically speed up compilation of C code for very little extra effort - provided that its cache survived between runs. The Travis builds do persist the build, but do not actually use ccache in any compilation (so the persisted cache is empty).
Expected behavior
ccache is used to accelerate compilation.
Actual behavior
ccache is not used to accelerate compilation.
Steps to Reproduce
Examine the Travis logs for a run. It will have a fold-away button marked ccache on the right side, but when unfolded the button reveals nothing was done.
System Details
This happens on all Travis builds (and all CircleCI too but I don't know if they support caching).
Suggested fix
Either just take the cache stanza out ot .travis.yml or enable ccache by setting the C compiler environment vairables to ccache gcc or ccache clang or the like.
The Travis cache is per-job, and there is one for master and another for each pull request; if a PR is missing its cache, it will pull the corresponding one from master.
Activity
pllim commentedon Nov 7, 2019
BTW, this is obsolete if we go ahead with #8445 .
saimn commentedon Nov 12, 2019
Travis is supposed to automatically add ccache to the $PATH, and this was working so it would be good to find why it stopped doing so.
Are you sure that it doesn't work ? https://travis-ci.org/astropy/astropy/jobs/610640501#L2161 for instance shows that it stores the cache. And https://travis-ci.org/astropy/astropy/caches shows that the cache is used (and we use it only for ccache).
One thing that may be misleading is that the cache is not shared across branches, I think.
aarchiba commentedon Nov 12, 2019
I may be wrong. I don't have permission to see the caches, and the Travis logs I've seen appear to show empty ccaches, but maybe I've been looking at the wrong ones. (Travis caches are inherited from master by PRs, and not shared between jobs.)