[LLVMdev] Quad-Core ARMv7 Build Slave Seeks Noble Purpose

Ben Pope
Thu, 14 Nov 2013 05:23:23 -0000

On 14/11/13 10:36, Mikael Lyngvig wrote:
> A quick question while I am adding a tiny section on ccache to the
> HowToAddABuilder document: Why do you set CCACHE_CPP2 to yes?  From reading
> the manual, I get the impression that this is much slower than the default
> and that it should only be used with tricky compilers or when debugging.
>  Is Clang such a tricky compiler?  If so, I suppose Clang should be fixed,
> not the ccache configuration.

Because ccache splits the compilation step up into components
(preprocess, compile, link, etc.), but passes all the options to each
stage, clang complains about unused build flags.

There might be other reasons that are not down to diagnostic noise, and
certainly ccache has had some of these issues fixed (it better knows
which options are suitable for which stage) since the recommendation
(I'm assuming they exist because it was tested with gcc which does not
complain so much).

Ben