[ccache] Why not cache compile failures?

[Andrew Stubbs]

Hi all,

I'm looking at ways to improve compile speed, and one obvious option is 
to cache compile failures. I'm thinking of certain non-called-for-link 
autoconf tests, in particular.

I'm aware that there's some danger here that we can end up caching 
Ctrl-C interrupts, SIGTERM/SIGKILL terminations, out-of-memory failures, 
and all manner of other non-reproducible failures, but these are the 
unusual case, and nothing that can't be fixed with CCACHE_RECACHE. I 
might suggest emitting an extra warning message that informs the user 
that they are seeing a cached failure.

Before I waste time trying to implement this, are there any other 
reasons for not doing this?

Has anybody else tried to do it already?

Thanks

Andrew