Re: [gentoo-portage-dev] [PATCH] ebuild: set up bash compat levels

[Michał Górny]

On Tue, 10 Nov 2015 23:39:29 -0500
Mike Frysinger <vapier@g.o> wrote:

> To try and provide better stability across bash versions,
> set the language compat level based on the current EAPI.
> ---
>  bin/eapi.sh   |  8 ++++++++
>  bin/ebuild.sh | 39 +++++++++++++++++++++++++++++++++++++++
>  2 files changed, 47 insertions(+)
>
> diff --git a/bin/eapi.sh b/bin/eapi.sh
> index 528e6f2..b236344 100644
> --- a/bin/eapi.sh
> +++ b/bin/eapi.sh
> @@ -191,3 +191,11 @@ ___eapi_enables_failglob_in_global_scope() {
>  ___eapi_enables_globstar() {
>  	[[ ${1-${EAPI-0}} =~ ^(4-python|5-progress)$ ]]
>  }
> +
> +__eapi_bash_3_2() {
> +	[[ ${1-${EAPI-0}} =~ ^(0|1|2|3|4|4-python|4-slot-abi|5|5-hdepend|5-progress)$ ]]
> +}
> +
> +__eapi_bash_4_2() {
> +	[[ ${1-${EAPI-0}} =~ ^(6)$ ]]
> +}
> diff --git a/bin/ebuild.sh b/bin/ebuild.sh
> index 75a9d24..2d09fb8 100755
> --- a/bin/ebuild.sh
> +++ b/bin/ebuild.sh
> @@ -6,8 +6,47 @@
>  # Make sure it's before everything so we don't mess aliases that follow.
>  unalias -a
>
> +# Make sure this isn't exported to scripts we execute.
> +unset BASH_COMPAT
> +
>  source "${PORTAGE_BIN_PATH}/isolated-functions.sh" || exit 1
>
> +# Set up the bash version compatibility level.
> +__check_bash_version() {
> +	# Figure out which min version of bash we require.
> +	local maj min
> +	if __eapi_bash_3_2 ; then
> +		maj=3 min=2
> +	elif __eapi_bash_4_2 ; then
> +		maj=4 min=2
> +	else
> +		return
> +	fi
> +
> +	# Make sure the active bash is sane.
> +	if [[ ${BASH_VERSINFO[0]} -lt ${maj} ]] ||
> +	   [[ ${BASH_VERSINFO[0]} -eq ${maj} && ${BASH_VERSINFO[1]} -lt ${min} ]] ; then
> +		die ">=bash-${maj}.${min} is required"
> +	fi
> +
> +	# Set the compat level in case things change with newer ones.  We must not
> +	# export this into the env otherwise we might break  other shell scripts we
> +	# execute (e.g. ones in /usr/bin).
> +	BASH_COMPAT="${maj}.${min}"
> +
> +	# The variable above is new to bash-4.3.  For older versions, we have to use
> +	# a compat knob.  Further, the compat knob only exists with older versions
> +	# (e.g. bash-4.3 has compat42 but not compat43).  This means we only need to
> +	# turn the knob with older EAPIs, and only when running newer bash versions:
> +	# there is no bash-3.3 (it went 3.2 to 4.0), and when requiring bash-4.2, the
> +	# var works with bash-4.3+, and you don't need to set compat to 4.2 when you
> +	# are already running 4.2.
> +	if __eapi_bash_3_2 && [[ ${BASH_VERSINFO[0]} -gt 3 ]] ; then
> +		shopt -s compat32
> +	fi
> +}
> +__check_bash_version
> +
>  if [[ $EBUILD_PHASE != depend ]] ; then
>  	source "${PORTAGE_BIN_PATH}/phase-functions.sh" || die
>  	source "${PORTAGE_BIN_PATH}/save-ebuild-env.sh" || die

I'm not convinced we ought to do this for EAPI < 6. It is a breaking
change after all, and as such changes the behavior of EAPI < 6 ebuilds.

There are some ebuilds/eclasses that have bash version checks,
and execute bash-4 code when bash-4 is available. As far as I
understand, this will effectively prohibit bash-4 code even though
BASH_VERSINFO will still indicate bash-4 is being used.

-- 
Best regards,
Michał Górny
<http://dev.gentoo.org/~mgorny/>