[ccache] Shared CCACHE_DIR, different ccache releases?

[Joel Rosdahl]

>
> How can I know if it's OK to use different versions of the ccache program
> with the same CCACHE_DIR location?


If you by "OK to use different versions" mean "works to share and reuse
cache results between different versions", then no, there are no such
guarantees and no list of compatible versions. I think that it would be too
much work to maintain such a list unless somebody volunteers to do that.

If you by "OK to use different versions" mean "works to use different
versions without damaging the cache or tripping up other ccache versions",
then yes, it should in principle work well to mix any ccache versions.
There might be edge cases that I'm unaware of at the moment, though.

Also, what is the convention regarding the version number? For instance, if
> only the last number changes as is my case, should CCACHE_DIR be generally
> compatible?


The version number doesn't give any guarantees about compatibility in the
"share results" sense. Increase of the last number: bug fixes and maybe
minor improvements other than bug fixes. Increase of the middle number:
Major improvements. Increase of the first number: Major improvements. :-)

-- Joel