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) 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)) -- Best Regards Masahiro Yamada -- 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
