Re: [PATCH regression 4.0 -> 4.1] tools perf: Fix build breakage if prefix= is specified

[Jiri Olsa <jolsa@redhat.com>]

On Thu, Jun 18, 2015 at 10:39:35PM +0200, Lukas Wunner wrote:
> Hi David,
> 
> On Thu, Jun 18, 2015 at 02:26:25PM -0600, David Ahern wrote:
> > It worked for me last week with OL6.
> > I created a standalone perf rpm with 4.1-rc6; it builds just fine with
> > _prefix (rpm variable) set to /usr:
> [...]
> > %global perf_make \
> >   make -s -C tools/perf V=1 WERROR=0 NO_LIBUNWIND=1 HAVE_CPLUS_DEMANGLE=1
> > NO_GTK2=1 NO_STRLCPY=1 NO_BIONIC=1 prefix=%{_prefix}
> > %{perf_make} DESTDIR=$RPM_BUILD_ROOT all
> 
> You're not invoking tools/perf/Makefile.perf but tools/perf/Makefile
> and I would say this in line 18 avoids that prefix= is passed down
> to Makefile.perf:
> 
> 	# We don't want to pass along options like -j:
> 	unexport MAKEFLAGS
> 
> Sources:
> https://www.gnu.org/software/make/manual/html_node/Options_002fRecursion.html
> https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/tree/tools/perf/Makefile#n18
> 
> So the prefix parameter should have no effect at all in your case,
> no matter to what you set it.

ouch, right:

"make automatically passes down variable values that were defined on the command line, by putting them in the MAKEFLAGS variable. See the next section. "

haven't realized Makefile.perf is used as primary makefile :-\

I think the patch is ok, I will try to come up with some tests
for this Makefile.perf usage.

thanks,
jirka