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

[Yann E. MORIN <yann.morin.1998@free.fr>]

Romain, All,

On 2019-03-10 17:59 +0100, Romain Naour spake thusly:
> 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@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))

This call is turned into:

    $(shell support/dependencies/check-host-python3.sh 3.4 python3 python)

which means that support/dependencies/check-host-python3.sh is called
with three arguments, not two, which means that...

> +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

... here we're left with two remaining arguments, and thus...

> +# 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"

... here ${1} is only ever going to contain "python3", not
"python3 python" as you think it does. Does it?

> +for candidate in $python3_candidates ; do

The simplest is to drop the python3_candidates variable, and simply use:

    for candidate in "${@}"; do
        [...]
    done

Regards,
Yann E. MORIN.

> +	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'`
> +
> +	major=`echo "$version" | cut -d. -f1`
> +	minor=`echo "$version" | cut -d. -f2`
> +
> +	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
> 
> _______________________________________________
> buildroot mailing list
> buildroot at busybox.net
> http://lists.busybox.net/mailman/listinfo/buildroot

-- 
.-----------------.--------------------.------------------.--------------------.
|  Yann E. MORIN  | Real-Time Embedded | /"\ ASCII RIBBON | Erics' conspiracy: |
| +33 662 376 056 | Software  Designer | \ / CAMPAIGN     |  ___               |
| +33 561 099 427 `------------.-------:  X  AGAINST      |  \e/  There is no  |
| http://ymorin.is-a-geek.org/ | _/*\_ | / \ HTML MAIL    |   v   conspiracy.  |
'------------------------------^-------^------------------^--------------------'