[lttng-dev] [PATCH lttng-ust] Fix: Corrected python version assumptions in lttng-gen-tp

Wed May 14 11:56:34 EDT 2014

On Wed, May 14, 2014 at 10:22 AM, Gerlando Falauto
<gerlando.falauto at keymile.com> wrote:
> Hi,
>
>
> On 05/13/2014 08:55 PM, Jérémie Galarneau wrote:
>>
>> On Tue, May 13, 2014 at 4:38 AM, Gerlando Falauto
>> <gerlando.falauto at keymile.com> wrote:
>>>
>>> Hi Jesper,
>>>
>>> [...]
>>>
>>>> I *thought* I was running on python2.7 but as it turns out I was not.
>>>>
>>>> When resolving "python" I get python2.7 but when I check the explicit
>>>> version laying at /usr/bin/python its actually a 2.4 version so no
>>>> wonder it
>>>> was failing.
>>>>
>>>> Checking the PEP for when "except XX as yy" was introduced points to
>>>> that
>>>> it was introduced in python 2.6 so entirely my mistake.
>>>> Reran it now with the a 2.7 version and it works as intended.
>>>>
>>>> However, I still think you should run it through env as proposed in the
>>>> patch and not use the explicit path to python.
>>>
>>>
>>>
>>> I still have some issues, even with this change.
>>> As a matter of fact, my default python installation would be a python2.6:
>>>
>>> $ python
>>>
>>> python
>>> Python 2.6.6 (r266:84292, Jan 22 2014, 05:06:49)
>>>
>>> I'm however cross-compiling, so I specify a sysroot and I explicitly set
>>> the
>>> python version in my configure script:
>>>
>>> $ . /opt/eldk/eldk_init ppc_6xx # set the env for cross-compiling
>>>
>>> $ python2.7
>>> Python 2.7.3 (default, Aug  2 2013, 20:37:10)
>>> [GCC 4.7.2] on linux2
>>>
>>> $ which python2.7
>>> /opt/eldk/powerpc/sysroots/i686-eldk-linux/usr/bin/python2.7
>>>
>>> $ ac_cv_header_linux_perf_event_h=no PYTHON=python2.7 ./configure
>>> --target=powerpc-linux --host=powerpc-linux --build=i686-linux
>>> --with-libtool-sysroot=/opt/eldk/powerpc/sysroots/powerpc-linux
>>> --prefix=/usr
>>>
>>> $ MAKEFLAGS= && DESTDIR=/opt/eldk/powerpc/sysroots/powerpc-linux make all
>>> install install-strip pkgconfigdir=/tmp pkgconfig_DATA=
>>>
>>> This doesn't however help, as the script will call "python" from the
>>> current
>>> environment (thereby ignoring the PYTHON= value used by the configure
>>> script
>>> when checking for python version).
>>>
>>> So perhaps a solution would be to change the configure script (or
>>> whatever
>>> it comes from by means of autoconfig/automake) so to create a "python"
>>> symlink in the working directory (to the version selected/detected) and
>>> then
>>> add it to the path (*).
>>>
>>> I guess a quick-and-dirty alternative could be to change the makefile so
>>> to
>>> use the "PYTHON" environment variable to explictly set what interpreter
>>> to
>>> use -- but that would defeat the whole purpose of the shebang so I
>>> believe
>>> it's a very bad idea:
>>>
>>> --- a/doc/examples/gen-tp/Makefile
>>> +++ b/doc/examples/gen-tp/Makefile
>>> @@ -46,7 +46,7 @@ sample.o: sample.c sample_tracepoint.h
>>>          CFLAGS="$(CFLAGS) $(AM_CFLAGS)" \
>>>          LDFLAGS="$(LDFLAGS) $(AM_LDFLAGS)" \
>>>          CC="$(CC)" \
>>> -       $(LTTNG_GEN_TP_PATH)lttng-gen-tp -o $@ $<
>>> +       $(PYTHON) $(LTTNG_GEN_TP_PATH)lttng-gen-tp -o $@ $<
>>>
>>>   # The following rule can be used to generate all files instead of
>>> having
>>> one
>>>   # for each file type. Note that the sample.o has a dependency on the
>>> @@ -55,10 +55,10 @@ sample.o: sample.c sample_tracepoint.h
>>>   #      lttng-gen-tp $<
>>>
>>>   %.h: %.tp
>>> -       $(LTTNG_GEN_TP_PATH)lttng-gen-tp -o $@ $<
>>> +       $(PYTHON) $(LTTNG_GEN_TP_PATH)lttng-gen-tp -o $@ $<
>>>
>>>   %.c: %.tp
>>> -       $(LTTNG_GEN_TP_PATH)lttng-gen-tp -o $@ $<
>>> +       $(PYTHON) $(LTTNG_GEN_TP_PATH)lttng-gen-tp -o $@ $<
>>>
>>>   .PHONY: clean
>>>   clean:
>>>
>>>
>>> What do you think?
>>>
>>
>> I agree that this is not the proper fix...
>>
>> Note that this script is not required to build lttng-ust. It will not
>> be used during the build process if your host doesn't have a suitable
>> Python version installed;
>
>
> Uhm, that's not entirely correct. Unfortunately, the configure script will
> indeed try detect a suitable python version; however, that doesn't mean it
> will use THAT version (in my case, the one reachable through "python2.7")
> when needed (and that's the whole point of my email!).
> I also tried enforcing detection of an older version (so to disable building
> of the examples) by using PYTHON=python before ./configure but I get:
>
> checking whether python version is >= 2.7... no
> configure: error: Python interpreter is too old
>

Which version of lttng-ust are you using? This has been fixed by

commit dcb6ba251f8c612133e4a3e064690d915f54a146
Author: Jérémie Galarneau <jeremie.galarneau at efficios.com>
Date:   Tue Apr 1 11:49:58 2014 -0400

    Fix: Override AM_PATH_PYTHON's default action-if-not-found

    AM_PATH_PYTHON's default action aborts configure. This fix ensures that
    configure follows through with a noop.

    Signed-off-by: Jérémie Galarneau <jeremie.galarneau at efficios.com>
    Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>

which is part of 2.4.1.

Regards,
Jérémie

> Some other attempts with am_* and ac_* variables led to similar results.
> In the end I settled for
>
> am_cv_pathless_PYTHON=none ./configure
>
> which at least lets me continue and disable BUILD_GEN_TP_EXAMPLES without
> touching the code.
>
>
>> it is only used to build one of the
>>
>> examples.
>
>
> Indeed.
>
>
>>
>> Regards,
>> Jérémie
>
>
> Thank you!
> Gerlando
>

-- 
Jérémie Galarneau
EfficiOS Inc.
http://www.efficios.com