[ccache] Build Safety

[Dalton, Tom]

Hi,

I think I know the answer to this question, but I want a second opinion!

In the past, I have used the Clearcase version control system, which has
it's own make system, clearmake. Clearmake provides some build caching
functionality (which it terms wink-ins), that allows it to 'wink-in'
build objects from other users views. I have experienced a lot of
problems with this system, because clearcase wouldn't detect that two
users were building the same file in a different environment (e.g.
external libraries at different versions. This caused me all sorts of
issues.

Is it possible for inconsistent environments between builds to cause
ccache to incorrectly use a cached object instead of recompiling? For
example, different builds of gcc, different external libraries etc? What
circumstances could cause this?

Secondly, if there is not much that can break ccache, is it possible to
use a shared cache (e.g. on an nfs-shared disk) to allow many users on
many hosts to cache build results across several versions of a single
product? (which will mean different gcc versions, libraries, even
kernels.)

Thanks for your help - ccache sounds really useful, but I want to make
sure there's no 'traps'!

Thanks,

Tom