[ccache] ccache test failures

[Joel Rosdahl]

On 16 March 2018 at 12:52, Forte, Greg via ccache
<ccache at lists.samba.org> wrote:
> Tried this with and without CCACHE_DIR set and exported - with it, I see the
> same output you showed, including the unset, and the test still fails: [...]

OK.

What's common between the two tests that fail for you is that you don't get a
cache hit for a second compilation in another directory. One way to understand
why is to log all data that is hashed by ccache in the two cases and see where
it starts to differ. There is a crude way of doing that already: Build ccache
with -DCCACHE_DEBUG_HASH and set CCACHE_DEBUG_HASH at runtime. Each ccache
invocation will then create a ccache-debug-hash.bin that contains the hashed
data, so you could compare the files in the two different directories. Or send
them to me (private mail) and I'll have a look.

By the way, here's a sketch of a yet unimplemented feature what would make this
kind of debugging easier: https://github.com/ccache/ccache/issues/226

-- Joel