On Sat, 2025-03-08 at 22:34 -0500, Ionen Wolkens wrote: > Sending this to dev ML in advance given it's simple and "probably" > won't need to change the code further. > > If interested in the whole deal, see the PR instead: > https://github.com/gentoo/gentoo/pull/40942 > > --- (actual commit message below) > > Both the slotting method and eclass are meant to be as simple > as possible, and isolated so that it does not really need to > work with everything given non-slotted ffmpeg stays. > > Did not want turn ffmpeg into a permanent slotting model with > a FFMPEG_SLOT use_expand, eselect, or such potentially turning > it into a special Gentoo-only thing that often need hacks. > > Essentially just a way for broken packages to gain time without > blocking everyone's ffmpeg updates. > > Signed-off-by: Ionen Wolkens <io...@gentoo.org> > --- > eclass/ffmpeg-compat.eclass | 69 +++++++++++++++++++++++++++++++++++++ > 1 file changed, 69 insertions(+) > create mode 100644 eclass/ffmpeg-compat.eclass > > diff --git a/eclass/ffmpeg-compat.eclass b/eclass/ffmpeg-compat.eclass > new file mode 100644 > index 000000000000..2d675ab4cc66 > --- /dev/null > +++ b/eclass/ffmpeg-compat.eclass > @@ -0,0 +1,69 @@ > +# Copyright 2025 Gentoo Authors > +# Distributed under the terms of the GNU General Public License v2 > + > +# @ECLASS: ffmpeg-compat.eclass > +# @MAINTAINER: > +# Ionen Wolkens <io...@gentoo.org> > +# @AUTHOR: > +# Ionen Wolkens <io...@gentoo.org> > +# @SUPPORTED_EAPIS: 8 > +# @BLURB: Helper functions to link with slotted ffmpeg-compat libraries > +# @DESCRIPTION: > +# To use this, run ``ffmpeg_compat_setup <slot>`` before packages use > +# pkg-config, depend on media-video/ffmpeg-compat:<slot>=, and ensure > +# usage of both pkg-config --cflags and --libs (which adds -Wl,-rpath > +# to find libraries at runtime). > +# > +# This eclass is intended as a quick-to-setup alternative to setting > +# an upper bound on ffmpeg for packages broken with the latest version, > +# and thus allow users to upgrade their normal ffmpeg. > +# > +# This should still be a temporary measure, and it is recommended to > +# keep migration bugs open rather than consider this eclass as being > +# the "fix". > +# > +# Unlike LLVM_SLOT-style, this does not have USE to select the slot > +# and should instead pick only the highest one usable until package > +# is fixed and can use non-slotted ffmpeg again. > +# > +# Do *not* use both like ``|| ( <ffmpeg-<ver> ffmpeg-compat:<slot> )``, > +# the package manager cannot know which version it linked against > +# without USE flags. Unfortunately means a period where users may > +# have two identical versions in stable before the newest major version > +# is stabilized, but idea is to not mangle normal ffmpeg with slotting > +# logic and make this an isolated temporary deal. > + > +case ${EAPI} in > + 8) ;; > + *) die "${ECLASS}: EAPI ${EAPI:-0} not supported" ;; > +esac > + > +if [[ -z ${_FFMPEG_COMPAT_ECLASS} ]]; then > +_FFMPEG_COMPAT_ECLASS=1 > + > +# @FUNCTION: ffmpeg_compat_get_prefix > +# @USAGE: <slot> > +# @DESCRIPTION: > +# Return prefix of the installed ffmpeg-compat:<slot>. Binaries like > +# ffmpeg will be found under <prefix>/bin if needed. > +ffmpeg_compat_get_prefix() { > + (( ${#} == 1 )) || die "Usage: ${FUNCNAME} <slot>" > + > + echo "${EPREFIX}/usr/lib/ffmpeg${1}" > +} > + > +# @FUNCTION: ffmpeg_compat_setup > +# @USAGE: <slot> > +# @DESCRIPTION: > +# Add ESYSROOT's ffmpeg-compat:<slot> to PKG_CONFIG_PATH for the > +# current ABI. Can be called multiple times for multilib. > +ffmpeg_compat_setup() { > + (( ${#} == 1 )) || die "Usage: ${FUNCNAME} <slot>" > + > + local path=${SYSROOT}$(ffmpeg_compat_get_prefix "${1}") > + [[ ${PKG_CONFIG_PATH} =~ (.*)"${path}"/[^/]+/pkgconfig:(.*) ]] && > + PKG_CONFIG_PATH=${BASH_REMATCH[1]}${BASH_REMATCH[2]} > + export > PKG_CONFIG_PATH=${path}/$(get_libdir)/pkgconfig:${PKG_CONFIG_PATH} > +} > + > +fi
I like this approach. We've generally been quite good at dragging upstreams to the latest, so it would be a shame to go fully slotted. The regex check seems like overkill to me, but perhaps I've missed something. This currently won't work when cross-compiling as cross-pkg-config currently unsets PKG_CONFIG_PATH, but I have been thinking about changing that. That was done to tame non-Gentoo environments, but no one else uses crossdev in reality.
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