Re: ./configure -C

[Stefan Kost <ensonic hora-obscura de>]

On 08/07/11 14:46, Andy Wingo wrote:
> Hello all,
>
> Brian Gough wrote, back in February [0]:
>
>   In his talk about Autotools at the FOSDEM GNU Dev Room, Ralf
>   Wildenheus mentioned an autoconf option that I wasn’t aware of. It’s
>   the “-C” option and it enables caching, which speeds up multiple runs
>   of a ./configure script enormously.
>
>   $ ./configure --help
>        --cache-file=FILE   cache test results in FILE [disabled]
>    -C, --config-cache      alias for `--cache-file=config.cache'
>   $ ./configure -C
>   configure: loading cache config.cache
>   ...
>
I've been using it too. The important thing is to delete the caches when
upgrading your distro. It always gets me into trouble when I noticed
that I forgot it.

While taking about it, another trick is "make -r". It skips loading
implicit rules, which autotools projects don't seem to depend on. It
especially helps when you rebuild a recursive project.

Stefan
>   Caching used to be the default up to about 10 years ago, but was
>   turned off as the cache gets out of sync with the system if new
>   packages are installed. Also it really only benefits developers, as
>   end-users typically only need to run ./configure once.
>
>   In the 1990′s I got used to caching being enabled by default and when
>   it was turned off I never noticed the change — except that somehow
>   running ./configure while developing seemed a lot slower in the past
>   ten years!
>
>   Thanks to Ralf for pointing out this option as I am now using -C all
>   the time.
>
> [0] http://blogs.fsfe.org/bjg/2011/02/autoconf-caching-an-option-i-didnt-know-about/
>
> It came to my attention that some GTK+ folks were not aware of this, as
> I wasn't, before seeing Ralf's presentation.  See
> http://www.gnu.org/s/hello/manual/autoconf/Cache-Files.html for more
> info.  I think you'll find that when hacking on your projects, it's
> quite useful!
>
> Cheers,
>
> Andy