gbuild, deps and ccache

Michael Stahl mstahl at
Fri Nov 9 05:45:45 PST 2012

On 09/11/12 14:04, Bjoern Michaelsen wrote:
> Hi,
> so the way gbuild generates dependencies prevents ccache to be confident about
> using its cache most of the time. To see this: do a/ build b/ make clean
> c/build from an empty ccache dir once with and without dep-tracking.
> The solution IMHO is to make gbuild run g++ twice, if building with deps and
> ccache:
>   g++ -E $(DEP_GEN_OPTIONS) $(OTHER) foo.cxx &&
>   ccache g++ $(OTHER) foo.cxx

> The first will then only generate the deps without compiling, while the second
> one will compile and not confuse ccache.

if invoking g++ twice in this silly fashion improves anything then that
sounds like a bug in ccache to me.  why don't you suggest fixing ccache
then instead of complicating our build system?

> So: Are there volunteers for this to make the build quite a bit faster for
> devs? If not I will have to EasyHackify this ...

please argue more convincingly why we need this.

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