Re: Bug 116411: tools/perf_clean: output directory does not exist. Stop.

[TJ]

Thanks for looking at this; I've become lost in Makefile hell trying to 
figure it out :)

On 15-04-2016 17:00, Arnaldo Carvalho de Melo wrote:
> Em Fri, Apr 15, 2016 at 03:21:35PM +0100, TJ escreveu:
> > v4.6-rc3
> > tools/perf then tools/perf_clean fails in the source tree:
> > *** output directory
> > "/home/all/SourceCode/linux/linux/tools/perf/tools/perf/" does not 
> > exist.
> > Stop.
> > https://bugzilla.kernel.org/show_bug.cgi?id=116411

----8-<---- snip

> I can reproduce the:
> [acme@jouet linux]$ rm -rf ../build/perf
>   [acme@jouet linux]$ mkdir ../build/perf
>   [acme@jouet linux]$ make O=../build/perf -C tools/perf
>   make: Entering directory '/home/acme/git/linux/tools/perf'
>     BUILD:   Doing 'make -j4' parallel build
>   ../scripts/Makefile.include:3: ***
> O=/home/acme/git/linux/tools/build/perf does not exist.  Stop.

----8-<---- snip
> > git blame shows commits c883122a and bf35182f are responsible for the 
> > path
> > calculation code.
> Thanks for narrowing it down, do you have any patch fixing this?

Over the last week I've exhaustively tried several alternative 
approaches, based around the idea of capturing the initial launch 
command-line O= value (since changing that for sub-makes is the problem 
here), but I've not been able to come up with a solution that works for 
all cases (srctree {relative,absolute} path or objtree 
{relative,absolute} path).

I'm also basing the command-line on the help from ./tools/Makefile 
which recommends:

  @echo ' $$ make -C tools/ <tool>_install'

I've added extensive debugging to track the changing variables from 
./tools/scripts/Makefile.include. The most successful for most 
situations (when starting from the base ./Makefile) captures BASE_O and 
then uses it for creating all paths, but the various subtle interactions 
of $(subdir) and the sub-makes, $(objtree), and others causes 
regressions such as generating output to the wrong directory.

diff --git a/tools/scripts/Makefile.include 
b/tools/scripts/Makefile.include
index 8abbef1..871c183 100644
--- a/tools/scripts/Makefile.include
+++ b/tools/scripts/Makefile.include
@@ -1,7 +1,11 @@
 ifneq ($(O),)
 ifeq ($(origin O), command line)
-       dummy := $(if $(shell test -d $(O) || echo $(O)),$(error O=$(O) 
does not exist),)
-       ABSOLUTE_O := $(shell cd $(O) ; pwd)
+ifeq ($(BASE_O),)
+       export BASE_O := $(abspath $(if $(filter ..% 
.%,$(O)),$(srctree)/$(O),$(O)))
+endif
+  __T := $(info BASE_O=$(BASE_O))
+       dummy := $(if $(shell test -d $(BASE_O) || echo 
$(BASE_O)),$(error BASE_O=$(BASE_O) does not exist),)
+       ABSOLUTE_O := $(shell cd $(BASE_O) ; pwd)
        OUTPUT := $(ABSOLUTE_O)/$(if $(subdir),$(subdir)/)
        COMMAND_O := O=$(ABSOLUTE_O)
 ifeq ($(objtree),)


Basing paths on BASE_O will fail (with incorrect paths) when starting 
the build directly with -C ./tools/ or  -C ./tools/perf/ -  it has felt 
like playing whack-a -mole!