[Buildroot] [PATCH] qt5: use ccache for building host code

[Peter Seiderer]

Hello Thomas,

On Sun, 4 Nov 2018 22:25:01 +0100, Thomas Petazzoni <thomas.petazzoni at bootlin.com> wrote:

> Hello Peter,
> 
> Thanks for looking at this patch!
> 
> On Sun, 4 Nov 2018 22:12:20 +0100, Peter Seiderer wrote:
> 
> > > +# This allows to use ccache when available
> > > +define QT5BASE_CONFIGURE_HOSTCC
> > > +	$(SED) 's,^QMAKE_COMPILER\s*=.*,QMAKE_COMPILER=$(HOSTCC),' $(@D)/mkspecs/common/g++-base.conf
> > > +	$(SED) 's,^QMAKE_CC\s*=.*,QMAKE_CC=$(HOSTCC),' $(@D)/mkspecs/common/g++-base.conf
> > > +	$(SED) 's,^QMAKE_CXX\s*=.*,QMAKE_CXX=$(HOSTCXX),' $(@D)/mkspecs/common/g++-base.conf
> > > +endef
> > > +    
> > 
> > With this sed commands applied, a qmake host compile is always using ccache (same
> > behavior already for the cross/target compile?)?  
> 
> I'm not sure to understand what you mean here. This change ensures that
> qmake is built with $(HOSTCC) / $(HOSTCXX) instead of gcc/g++.
> 
> HOSTCC is set to "gcc" and HOSTCXX to "g++", except when BR2_CCACHE=y,
> in which case HOSTCC is "ccache gcc" and HOSTCXX is "ccache g++".
> 
> So basically, this patch ensures that qmake is built with what
> Buildroot considers to be the "host compiler", which may or may not
> have ccache enabled.
> 
> Does this answer your question, or perhaps I misunderstood it
> completely ?

Thanks for the answer (you got it right)...., so in case I use the
buildroot-generated qmake I will always use ccache (if configured),
even if used outside of the buildroot build system, right?

The $(HOSTCC) is expanded at the sed command running time,
g++-base.conf will contain 'QMAKE_COMPILER=gcc' or
'QMAKE_COMPILER=ccache gcc'...

Not sure if this matters for some use cases...

Regards,
Peter

> 
> Thanks!
> 
> Thomas