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

[Jérémie Galarneau]

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; it is only used to build one of the
examples.

Regards,
Jérémie

> Thank you!
> Gerlando
>
> (*) As suggested by
> http://redsymbol.net/articles/env-and-python-scripts-version/
>
>
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-- 
Jérémie Galarneau
EfficiOS Inc.
http://www.efficios.com