[Buildroot] About python2 and python3

[Buildroot] About python2 and python3

[Marco Trapanese]

Hi,
if python2 is selected is not possible to add python3.
But python2 and python3 are quite different and sometimes is useful to 
have both. i cannot deselect python2 because is selected by another package.

I tried to force the compilation of python3 (removing the dependency 
from python2) but the dbus module is not found.
Instead python2 finds the dbus module, but complains about the missing 
of xml.parsers.expat module.

I checked and BR2_PACKAGE_PYTHON*_PYEXPAT are selected.

Just for info I need this to run the ofono tests.

[Buildroot] About python2 and python3

[Thomas Petazzoni]

Hello,

On Mon, 9 May 2016 22:16:46 +0200, Marco Trapanese wrote:

> if python2 is selected is not possible to add python3.
> But python2 and python3 are quite different and sometimes is useful to 
> have both. i cannot deselect python2 because is selected by another package.

We currently do not support building both Python 2 and Python 3.

The main reason is that we allow building external Python modules, and
it would be very annoying with Kconfig to allow the user to tell which
modules should be built/installed for Python 2, which modules should be
built/installed for Python 3, and which modules should be
built/installed for both.

One possibility would be to install all of them for both Python 2 and
Python 3, but that's very inefficient.

So, I think we'll stick with just supporting the installation of either
Python 2 or Python 3. I'd rather recommend you to see why you need
Python 2 at all, and try to see if you can make that part work with
Python 3.

Best regards,

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

[Buildroot] About python2 and python3

[Marco Trapanese]

Il 09/05/2016 22:26, Thomas Petazzoni ha scritto:
> So, I think we'll stick with just supporting the installation of 
> either Python 2 or Python 3. I'd rather recommend you to see why you 
> need Python 2 at all, and try to see if you can make that part work 
> with Python 3. 

Ok, it's reasonable.
Is there an easy way to find out which package(s) is selecting another?
I had to copy & paste several times the loooong "selected by" line:

> Selected by:
>
> BR2_PACKAGE_KODI [=n] &&
> BR2_INSTALL_LIBSTDCPP [=y] &&
> BR2_HOST_GCC_AT_LEAST_4_6 [=y] &&
> BR2_TOOLCHAIN_GCC_AT_LEAST_4_7 [=y] &&
> BR2_TOOLCHAIN_HAS_THREADS [=y] &&
> !BR2_TOOLCHAIN_USES_MUSL [=n] &&
> (BR2_PACKAGE_KODI_EGL_GLES [=y] ||
> BR2_PACKAGE_KODI_GL [=n]) &&
> BR2_USE_MMU [=y] &&
> BR2_USE_WCHAR [=y] &&
> !BR2_STATIC_LIBS [=n] &&
> BR2_PACKAGE_KODI_ARCH_SUPPORTS [=y] ||
> BR2_PACKAGE_DSTAT [=n] &&
> BR2_USE_WCHAR [=y] &&
> BR2_USE_MMU [=y] &&
> BR2_TOOLCHAIN_HAS_THREADS [=y] &&
> !BR2_STATIC_LIBS [=n] ||
> BR2_PACKAGE_SAMBA4 [=y] &&
> BR2_USE_MMU [=y] &&
> BR2_USE_WCHAR [=y] &&
> BR2_TOOLCHAIN_HAS_NATIVE_RPC [=y] &&
> BR2_TOOLCHAIN_HAS_THREADS [=y] &&
> !BR2_STATIC_LIBS [=n] &&
> !BR2_nios2 [=n] &&
> BR2_TOOLCHAIN_HAS_SYNC_4 [=y]

I guess the && operator has the precedence. So this should be read like:

(BR2_PACKAGE_KODI [=n] && BR2_INSTALL_LIBSTDCPP [=y] && 
BR2_HOST_GCC_AT_LEAST_4_6 [=y] && BR2_TOOLCHAIN_GCC_AT_LEAST_4_7 [=y] && 
BR2_TOOLCHAIN_HAS_THREADS [=y] && !BR2_TOOLCHAIN_USES_MUSL [=n] && 
(BR2_PACKAGE_KODI_EGL_GLES [=y])

  ||

(BR2_PACKAGE_KODI_GL [=n]) && BR2_USE_MMU [=y] && BR2_USE_WCHAR [=y] && 
!BR2_STATIC_LIBS [=n] && BR2_PACKAGE_KODI_ARCH_SUPPORTS [=y])

  ||

(BR2_PACKAGE_DSTAT [=n] && BR2_USE_WCHAR [=y] && BR2_USE_MMU [=y] && 
BR2_TOOLCHAIN_HAS_THREADS [=y] && !BR2_STATIC_LIBS [=n])

  ||

(BR2_PACKAGE_SAMBA4 [=y] && BR2_USE_MMU [=y] && BR2_USE_WCHAR [=y] && 
BR2_TOOLCHAIN_HAS_NATIVE_RPC [=y] && BR2_TOOLCHAIN_HAS_THREADS [=y] && 
!BR2_STATIC_LIBS [=n] && !BR2_nios2 [=n] && BR2_TOOLCHAIN_HAS_SYNC_4[=y])

so it's the last group which selects python2: samba4.
Right now I've deselected it. Then I will try to understand if it can 
live with python3.

Best regards
Marco

[Buildroot] About python2 and python3

[Thomas Petazzoni]

Hello,

On Mon, 9 May 2016 23:00:51 +0200, Marco Trapanese wrote:

> Ok, it's reasonable.
> Is there an easy way to find out which package(s) is selecting another?
> I had to copy & paste several times the loooong "selected by" line:

Run "make graph-depends" and look into output/graphs/.

> so it's the last group which selects python2: samba4.
> Right now I've deselected it. Then I will try to understand if it can 
> live with python3.

Most likely not. Samba is a big thing, and making it work with Python 3
is going to be a huge amount of work if it's not done by upstream.

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com