[Buildroot] [PATCH 1/2] support/dependencies: add a check for python3

[Romain Naour]

Hi Adam,

Le 12/03/2019 à 14:09, Adam Duskett a écrit :
> Hello;
> On Sun, Mar 10, 2019 at 12:59 PM Romain Naour <romain.naour at gmail.com> wrote:
>>
>> Since version 2.29, glibc requires python 3.4 or later to build the GNU C Library [1].
>>
>> We add a new check to verify the version of python3 interpreter installed on the host.
>> If no suitable python3 interpreter is found, define BR2_PYTHON3_HOST_DEPENDENCY to add
>> host-python3 in package dependencies when needed.
>>
>> [1] https://www.sourceware.org/ml/libc-alpha/2019-01/msg00723.html
>>
>> Signed-off-by: Romain Naour <romain.naour at gmail.com>
>> ---
>>  support/dependencies/check-host-python3.mk | 13 ++++++++++
>>  support/dependencies/check-host-python3.sh | 41 ++++++++++++++++++++++++++++++
>>  2 files changed, 54 insertions(+)
>>  create mode 100644 support/dependencies/check-host-python3.mk
>>  create mode 100755 support/dependencies/check-host-python3.sh
>>
>> diff --git a/support/dependencies/check-host-python3.mk b/support/dependencies/check-host-python3.mk
>> new file mode 100644
>> index 0000000000..ceb48c969e
>> --- /dev/null
>> +++ b/support/dependencies/check-host-python3.mk
>> @@ -0,0 +1,13 @@
>> +# Since version 2.29, glibc requires python 3.4 or later to build the GNU C Library.
>> +# https://www.sourceware.org/ml/libc-alpha/2019-01/msg00723.html
>> +
>> +# Set this to either 3.4 or higher, depending on the highest minimum
>> +# version required by any of the packages bundled in Buildroot. If a
>> +# package is bumped or a new one added, and it requires a higher
>> +# version, our package infra will catch it and whine.
>> +#
>> +BR2_PYTHON3_VERSION_MIN = 3.4
>> +
>> +ifeq (,$(call suitable-host-package,python3,$(BR2_PYTHON3_VERSION_MIN) python3 python))
>> +BR2_PYTHON3_HOST_DEPENDENCY = host-python3
>> +endif
>> diff --git a/support/dependencies/check-host-python3.sh b/support/dependencies/check-host-python3.sh
>> new file mode 100755
>> index 0000000000..e5745fa7c4
>> --- /dev/null
>> +++ b/support/dependencies/check-host-python3.sh
>> @@ -0,0 +1,41 @@
>> +#!/bin/sh
>> +
>> +# prevent shift error
>> +[ $# -lt 2 ] && exit 1
>> +
>> +major_min="${1%.*}"
>> +minor_min="${1#*.}"
>> +
>> +shift
>> +
>> +# The host python interpreter is already checked by dependencies.sh but
>> +# it only check if the version is at least 2.7.
>> +# We want to check the version number of the python3 interpreter even
>> +# if Buildroot is able to use any version but some packages may require
>> +# a more recent version.
>> +python3_candidates="$1"
>> +
>> +for candidate in $python3_candidates ; do
>> +       python3=`which $candidate 2>/dev/null`
>> +       if [ ! -x "$python3" ]; then
>> +               continue
>> +       fi
>> +       version=`$python3 -V 2>&1 | sed -e 's/^.* \([0-9\.]\)/\1/g' -e 's/[-].*//g' -e '1q'`
> I personally prefer the syntax foo=$(command) rather than foo=`$command`

I tried to keep the same convention as for other check-host-*.sh script. (see
check-host-cmake.sh).

>> +
>> +       major=`echo "$version" | cut -d. -f1`
>> +       minor=`echo "$version" | cut -d. -f2`
>> +
> I have a bit of issue with this:
> Why can't we use the same line as we use in dependencies.sh?
> version=$(python3 -V 2>&1 |awk '{ split($2, v, "."); print v[1] v[2] }')
> On Fedora29 this produces 37, which makes the check much easier.

It should be possible, I'll try.
I want to keep BR2_PYTHON3_VERSION_MIN = 3.4.

> 
>> +       if [ $major -lt $major_min ]; then
>> +               # no suitable python3 found
>> +               continue
>> +       fi
>> +
>> +       if [ $major -eq $major_min -a $minor -lt $minor_min ]; then
>> +               # no suitable python3 found
>> +               continue
>> +       fi
>> +
>> +       # suitable python3 found
>> +       echo $python3
>> +       break
>> +done
>> --
>> 2.14.5
> Is there a reason this logic can't go in dependencies.sh?

We need to define "BR2_PYTHON3_HOST_DEPENDENCY = host-python3" from the Makefile
(check-host-python3.mk) if no suitable python3 is found on the host.

BR2_PYTHON3_HOST_DEPENDENCY is used latter by glibc.mk to add host-python3 in
GLIBC_DEPENDENCIES only if the python installed on the host is python2 or a too
old python3.

I don't see how we can do that if the logic is located in dependencies.sh.

Thanks for the review.
Romain

> 
>>
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> 
> Thanks!
> Adam
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