Re: [PATCH] tools: probe for existence of qemu-xen trace backends.

[Anthony PERARD <anthony.perard@citrix.com>]

On Wed, Feb 10, 2016 at 02:14:13PM +0000, Stefano Stabellini wrote:
> On Wed, 10 Feb 2016, Ian Campbell wrote:
> > diff --git a/tools/Makefile b/tools/Makefile
> > index 5688a7c..76a2235 100644
> > --- a/tools/Makefile
> > +++ b/tools/Makefile
> > @@ -228,7 +228,7 @@ qemu-xen-dir-force-update: qemu-xen-dir-find
> >  	fi
> >  
> >  ifeq ($(debug),y)
> > -QEMU_XEN_ENABLE_DEBUG := --enable-debug --enable-trace-backend=stderr
> > +QEMU_XEN_ENABLE_DEBUG := --enable-debug
> >  else
> >  QEMU_XEN_ENABLE_DEBUG :=
> >  endif
> > @@ -240,8 +240,16 @@ subdir-all-qemu-xen-dir: qemu-xen-dir-find
> >  		source=.; \
> >  	fi; \
> >  	cd qemu-xen-dir; \
> > +	if $$source/scripts/tracetool.py --check-backends --backends log ; then \
> 
> --check-backends only works on qemu-xen >= 4.6, on the other hand we
> know that qemu-xen < 4.6 supports stderr.

But, if you use '--check-backend --backend' (no 's') instead, the check
would works with qemu-xen >= 4.3

> Maybe:
> 
> if $$source/scripts/tracetool.py --check-backends --backends log &>/dev/null
> then
>     enable_trace_backend='--enable-trace-backend=log'
> else
>     enable_trace_backend='--enable-trace-backend=stderr'
> fi
> 
> ?
> 
> 
> > +		enable_trace_backend='--enable-trace-backend=log'; \
> > +	elif $$source/scripts/tracetool.py --check-backends --backends stderr ; then \
> > +		enable_trace_backend='--enable-trace-backend=stderr'; \
> > +	else \
> > +		enable_trace_backend='' ; \
> > +	fi ; \
> >  	$$source/configure --enable-xen --target-list=i386-softmmu \
> >  		$(QEMU_XEN_ENABLE_DEBUG) \
> > +		$$enable_trace_backend \
> >  		--prefix=$(LIBEXEC) \
> >  		--libdir=$(LIBEXEC_LIB) \
> >  		--includedir=$(LIBEXEC_INC) \
> > -- 
> > 2.1.4
> > 

-- 
Anthony PERARD