Improving verrou_dd cache invalidation

[HadrienG2]

verrou_dd only invalidates its cache when the run-script or the cmp-script change. But these scripts usually recursively call other binaries or touch configuration files which verrou_dd has no knowledge of. Therefore, the dd.sym cache is often reused when it shouldn't be.

I propose two possible strategies to deal with this, a sane but unsatisfying one an a less sane but more powerful strategy:

• Sane-but-meh option: Invalidate the cache by default when a top-level verrou_dd command is run. If the command calls itself recursively, make sure that the recursive invocations do not invalidate the cache. This can be done by adding an optional "--reuse-cache" script option, which will also allow users who know what they are doing to reuse a cache from a previous run.
• Insane option: In principle, one could strace run-script or cmp-script calls in order to tell which files the run_script and cmp_script recursively depend on, and then compute a hash of them to detect dependency changes... ^^

[ffevotte]

verrou_dd only invalidates its cache when the run-script or the cmp-script change

Please note that even this simple heuristic is not used currently. At the moment, Verrou never invalidates its cache which, as you note, is not a good idea as it misleads users most of the time.

I would be in favor of implementing your 'sane-but-meh' option in a first stage, then see whether more is needed. We also have a few ideas regarding helper scripts which could allow (advanced) users to invalidate only parts of the cache. For example: invalidate successful tests if a verrou_dd error reveals that VERROU_DD_NRUNS was set to a too small value).

[lathuili]

Since the v2.3.1version you can configure the cache behaviour with the option --cache.