[Buildroot] [PATCH] ccache: make default host-ccache cache dir fit for multi-user setups

[Thomas Petazzoni <thomas.petazzoni@free-electrons.com>]

Hello,

On Thu,  6 Jul 2017 12:48:41 +0200, Peter Korsgaard wrote:
> While building I noticed:
> 
> >>> host-ccache 3.3.4 Building  
> conf.c: In function 'conf_create':
> conf.c:314:2: warning: too many arguments for format [-Wformat-extra-args]
>   conf->cache_dir = format("/home/peko/.buildroot-ccache", get_home_directory());
>   ^
> 
> As host-ccache gets installed into $(HOST_DIR) and is part of the SDK,
> hardcoding the build user homedir isn't really nice for the relocatable
> SDK feature (or simply for a SDK used by multiple users).
> 
> As the warning shows, CCache replaces "%s" with the current user home
> directory, so rewrite BR_CACHE_DIR to use this feature if it begins with
> $HOME.
> 
> Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
> ---
>  package/ccache/ccache.mk | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/package/ccache/ccache.mk b/package/ccache/ccache.mk
> index 97d66bb45b..afbec44fac 100644
> --- a/package/ccache/ccache.mk
> +++ b/package/ccache/ccache.mk
> @@ -28,9 +28,13 @@ HOST_CCACHE_CONF_OPTS += --with-bundled-zlib
>  #    BR2_CCACHE_DIR.
>  #  - Change hard-coded last-ditch default to match path in .config, to avoid
>  #    the need to specify BR_CACHE_DIR when invoking ccache directly.
> +#    CCache replaces "%s" with the home directory of the current user,
> +#    So rewrite BR_CACHE_DIR to take that into consideration for SDK purpose
> +HOST_CCACHE_DEFAULT_CCACHE_DIR = $(patsubst $(HOME)/%,\%s/%,$(BR_CACHE_DIR))

But this only solves the problem for the specific case where the ccache
cache is inside the same folder in user A home directory and user B
home directory.

If I set BR2_CCACHE_DIR to /home/thomas/projects/foobar/ccache/, which
works on my machine, you most likely won't
have /home/jacmet/projects/foobar/ccache/ on your machine.

So I have the feeling that this only solves the problem for the
specific case where the ccache cache is directly in a sub-directory of
the home folder. Any other situation will continue to fail, and will
anyway require a different solution, that would also fix the specific
home folder case.

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com