On Tue, Feb 06, 2018 at 07:44:22PM +0900, Masahiro Yamada wrote: > 2018-02-06 18:34 GMT+09:00 Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>: > > On Tue, Feb 06, 2018 at 09:34:46AM +0900, Masahiro Yamada wrote: > >> The variable 'PYTHON' allows users to specify a proper executable > >> name in case the default 'python' does not work. However, this does > >> not address the case where both Python 2 and Python 3 scripts are > >> used in one system. > >> > >> PEP 394 (https://www.python.org/dev/peps/pep-0394/) provides a > >> convention for Python scripts portability. Here is a quotation: > >> > >> In order to tolerate differences across platforms, all new code > >> that needs to invoke the Python interpreter should not specify > >> 'python', but rather should specify either 'python2' or 'python3'. > >> This distinction should be made in shebangs, when invoking from a > >> shell script, when invoking via the system() call, or when invoking > >> in any other context. > >> > >> arch/ia64/scripts/unwcheck.py is apparently written in Python 2, so > >> it should be invoked by 'python2'. > >> > >> It is legitimate to use 'python' for scripts compatible with both > >> Python 2 and Python 3, but this is rare (at least I do not see the > >> case in kernel tree). You do not need to make efforts to write your > >> scripts in that way. Anyway, Python 2 will retire in 2020. > >> > >> This commit is needed for my new scripts written in Python 3. > >> > >> Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx> > >> --- > >> > >> Makefile | 5 +++-- > >> arch/ia64/Makefile | 2 +- > >> 2 files changed, 4 insertions(+), 3 deletions(-) > >> > >> diff --git a/Makefile b/Makefile > >> index 11aff0f..c4e935c 100644 > >> --- a/Makefile > >> +++ b/Makefile > >> @@ -384,7 +384,8 @@ GENKSYMS = scripts/genksyms/genksyms > >> INSTALLKERNEL := installkernel > >> DEPMOD = /sbin/depmod > >> PERL = perl > >> -PYTHON = python > >> +PYTHON2 = python2 > >> +PYTHON3 = python3 > > > > Is this going to break any systems that were previous setting PYTHON? > > > > I like this change, and feel it is the correct thing to do, but having a > > "fallback" might be needed here. > > > > Could you do what the perf makefile does and do something like: > > override PYTHON := $(call get-executable-or-default,PYTHON,$(PYTHON2)) > > or is it really not an issue as only ia64 seems to care about this? > > > > As far as I see, ia64 is the only instance that has used this ever. > > (the perf Makefile defines PYTHON by itself, so should not be a problem.) > > > If people expect the backward-compatibility for this, I can do like follows: > > # backward compatibility for 'PYTHON' > PYTHON2 := $(if $(PYTHON), $(PYTHON), python2) That's true, and who knows if python3 is running on ia64 :) > Another (unlikely) possible breakage is > 'python2' may not be installed on users' system. > > I believe this is rare, but if needed, I could do like follows > at the cost of ugliness. > > > PYTHON2 := $(if $(PYTHON), $(PYTHON), \ > $(shell python2 --version 2>/dev/null && echo python2 || echo python)) Ick, I guess that might work. Try getting your patch set into the 0-day system to see how it handles things. I know it builds for ia64. But this is a real tiny question overall, and should not derail this patchset at all :) thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
