Re: [PATCH v9 1/4] Create source symlink in perf object dir

[Andi Kleen <ak@linux.intel.com>]

On Mon, Nov 25, 2024 at 06:25:06PM +0100, Luca Ceresoli wrote:
> Hello Andi,
> 
> +cc Yann and the Buildroot mailing list (see the end of this report).
> 
> On Wed,  7 Aug 2024 16:18:20 -0700
> Andi Kleen <ak@linux.intel.com> wrote:
> 
> > Create a source symlink to the original source in the objdir.
> > This is similar to what the main kernel build script does.
> > 
> > Signed-off-by: Andi Kleen <ak@linux.intel.com>
> > ---
> >  tools/perf/Makefile.perf | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
> > index 175e4c7898f0..d46892d8223b 100644
> > --- a/tools/perf/Makefile.perf
> > +++ b/tools/perf/Makefile.perf
> > @@ -163,6 +163,8 @@ ifneq ($(OUTPUT),)
> >  # for flex/bison parsers.
> >  VPATH += $(OUTPUT)
> >  export VPATH
> > +# create symlink to the original source
> > +SOURCE := $(shell ln -sf $(srctree)/tools/perf $(OUTPUT)/source)
> 
> I found that since this patch got applied in 890a1961c812 (v6.12-rc1)
> building perf fails silently in some cases.
> 
> The cases I have tested:
>  - make <FLAGS> -C tools/perf                       -> OK
>  - make <FLAGS> -C tools/perf O=/my/out/of/tree/dir -> OK
>  - make <FLAGS> -C tools/perf O=tools/perf          -> fails
> 
> The failure in the third case is silent: make exits with a return value
> of 0, but there is no perf executable created.

The failing case is incorrect arguments because the O= is relative to -C 
and there is no tools/perf/tools/perf

But yes a error message would be good.

Could just ignore the linking error, so that you hopefully get a better
error message later.

diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
index 9dd2e8d3f3c9..18f639ec853b 100644
--- a/tools/perf/Makefile.perf
+++ b/tools/perf/Makefile.perf
@@ -164,7 +164,7 @@ ifneq ($(OUTPUT),)
 VPATH += $(OUTPUT)
 export VPATH
 # create symlink to the original source
-SOURCE := $(shell ln -sf $(srctree)/tools/perf $(OUTPUT)/source)
+SOURCE := $(shell ln -sf $(srctree)/tools/perf $(OUTPUT)/source || true)
 endif
 
 ifeq ($(V),1)