llvm-r1.eclass: Initial version

Bug: https://bugs.gentoo.org/923228
Bug: https://bugs.gentoo.org/880671
Closes: https://bugs.gentoo.org/821955
Closes: https://bugs.gentoo.org/919150
Signed-off-by: Michał Górny <mgorny@gentoo.org>

1 files changed, 250 insertions, 0 deletions

diff --git a/eclass/llvm-r1.eclass b/eclass/llvm-r1.eclass
new file mode 100644
index 000000000000..658946a1ecbd
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+++ b/eclass/llvm-r1.eclass
@@ -0,0 +1,250 @@
+# Copyright 2024 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+# @ECLASS: llvm-r1.eclass
+# @MAINTAINER:
+# Michał Górny <mgorny@gentoo.org>
+# @AUTHOR:
+# Michał Górny <mgorny@gentoo.org>
+# @SUPPORTED_EAPIS: 8
+# @PROVIDES: llvm-utils
+# @BLURB: Provide LLVM_SLOT to build against slotted LLVM
+# @DESCRIPTION:
+# An eclass to reliably depend on a set of LLVM-related packages
+# in a matching slot.  To use the eclass:
+#
+# 1. Set LLVM_COMPAT to the list of supported LLVM slots.
+# 2. Use llvm_gen_dep and/or LLVM_USEDEP to add appropriate
+#    dependencies.
+# 3. Use llvm-r1_pkg_setup, get_llvm_prefix or LLVM_SLOT.
+#
+# The eclass sets IUSE and REQUIRED_USE.  The flag corresponding
+# to the newest supported stable LLVM slot (or the newest testing,
+# if no stable slots are supported) is enabled by default.
+#
+# Example:
+# @CODE
+# LLVM_COMPAT=( {16..18} )
+#
+# inherit llvm-r1
+#
+# DEPEND="
+#   dev-libs/libfoo[${LLVM_USEDEP}]
+#   $(llvm_gen_dep '
+#     sys-devel/clang:${LLVM_SLOT}
+#     sys-devel/llvm:${LLVM_SLOT}
+#   ')
+# "
+# @CODE
+
+case ${EAPI} in
+	8) ;;
+	*) die "${ECLASS}: EAPI ${EAPI:-0} not supported" ;;
+esac
+
+if [[ ! ${_LLVM_R1_ECLASS} ]]; then
+_LLVM_R1_ECLASS=1
+
+inherit llvm-utils
+
+# == internal control knobs ==
+
+# @ECLASS_VARIABLE: _LLVM_OLDEST_SLOT
+# @INTERNAL
+# @DESCRIPTION:
+# Oldest supported LLVM slot.  This is used to automatically filter out
+# unsupported LLVM_COMPAT values.
+_LLVM_OLDEST_SLOT=15
+
+# @ECLASS_VARIABLE: _LLVM_NEWEST_STABLE
+# @INTERNAL
+# @DESCRIPTION:
+# The newest stable LLVM version.  Versions newer than that won't
+# be automatically enabled via USE defaults.
+_LLVM_NEWEST_STABLE=17
+
+# == control variables ==
+
+# @ECLASS_VARIABLE: LLVM_COMPAT
+# @PRE_INHERIT
+# @REQUIRED
+# @DESCRIPTION:
+# A list of LLVM slots supported by the package, oldest to newest.
+#
+# Example:
+# @CODE
+# LLVM_COMPAT=( {15..17} )
+# @CODE
+
+# @ECLASS_VARIABLE: LLVM_OPTIONAL
+# @PRE_INHERIT
+# @DEFAULT_UNSET
+# @DESCRIPTION:
+# If set to a non-empty value, disables setting REQUIRED_USE
+# and exporting pkg_setup.  You have to add LLVM_REQUIRED_USE and call
+# pkg_setup manually, with appropriate USE conditions.
+
+# == global metadata ==
+
+# @ECLASS_VARIABLE: LLVM_REQUIRED_USE
+# @OUTPUT_VARIABLE
+# @DESCRIPTION:
+# An eclass-generated REQUIRED_USE string that enforces selecting
+# exactly one slot.  It LLVM_OPTIONAL is set, it needs to be copied
+# into REQUIRED_USE, under appropriate USE conditions.  Otherwise,
+# it is added automatically.
+
+# @ECLASS_VARIABLE: LLVM_USEDEP
+# @OUTPUT_VARIABLE
+# @DESCRIPTION:
+# An eclass-generated USE dependency string that can be applied to other
+# packages using the same eclass, to enforce a LLVM slot match.
+
+_llvm_set_globals() {
+	debug-print-function ${FUNCNAME} "${@}"
+
+	if [[ ${LLVM_COMPAT@a} != *a* ]]; then
+		die "LLVM_COMPAT must be set to an array before inheriting ${ECLASS}"
+	fi
+
+	local stable=() unstable=()
+	local x
+	for x in "${LLVM_COMPAT[@]}"; do
+		if [[ ${x} -gt ${_LLVM_NEWEST_STABLE} ]]; then
+			unstable+=( "${x}" )
+		elif [[ ${x} -ge ${_LLVM_OLDEST_SLOT} ]]; then
+			stable+=( "${x}" )
+		fi
+	done
+
+	_LLVM_SLOTS=( "${stable[@]}" "${unstable[@]}" )
+	if [[ ! ${_LLVM_SLOTS[@]} ]]; then
+		die "LLVM_COMPAT does not contain any valid versions (all older than ${_LLVM_OLDEST_SLOT}?)"
+	fi
+
+	if [[ ${stable[@]} ]]; then
+		IUSE="+llvm_slot_${stable[-1]}"
+		unset 'stable[-1]'
+	else
+		IUSE="+llvm_slot_${unstable[-1]}"
+		unset 'unstable[-1]'
+	fi
+	local nondefault=( "${stable[@]}" "${unstable[@]}" )
+	IUSE+=" ${nondefault[*]/#/llvm_slot_}"
+
+	local flags=( "${_LLVM_SLOTS[@]/#/llvm_slot_}" )
+	LLVM_REQUIRED_USE="^^ ( ${flags[*]} )"
+	local usedep_flags=${flags[*]/%/(-)?}
+	LLVM_USEDEP=${usedep_flags// /,}
+	readonly LLVM_REQUIRED_USE LLVM_USEDEP
+
+	if [[ ! ${LLVM_OPTIONAL} ]]; then
+		REQUIRED_USE=${LLVM_REQUIRED_USE}
+	fi
+}
+_llvm_set_globals
+unset -f _llvm_set_globals
+
+# == metadata helpers ==
+
+# @FUNCTION: llvm_gen_dep
+# @USAGE: <dependency>
+# @DESCRIPTION:
+# Output a dependency block, repeating "<dependency>" conditionally
+# to all llvm_slot_* USE flags.  Any occurences of '${LLVM_SLOT}'
+# within the block will be substituted for the respective slot.
+#
+# Example:
+# @CODE
+# DEPEND="
+#   $(llvm_gen_dep '
+#     sys-devel/clang:${LLVM_SLOT}
+#     sys-devel/llvm:${LLVM_SLOT}
+#   ')
+# "
+# @CODE
+llvm_gen_dep() {
+	debug-print-function ${FUNCNAME} "${@}"
+
+	[[ ${#} -ne 1 ]] && die "Usage: ${FUNCNAME} <dependency>"
+
+	local dep=${1}
+
+	local slot
+	for slot in "${_LLVM_SLOTS[@]}"; do
+		echo "llvm_slot_${slot}? ( ${dep//\$\{LLVM_SLOT\}/${slot}} )"
+	done
+}
+
+# == ebuild helpers ==
+
+# @FUNCTION: get_llvm_prefix
+# @USAGE: [-b|-d]
+# @DESCRIPTION:
+# Output the path to the selected LLVM slot.
+#
+# With no option or "-d", the path is prefixed by ESYSROOT.  LLVM
+# dependencies should be in DEPEND then.
+#
+# With "-b" option, the path is prefixed by BROOT. LLVM dependencies
+# should be in BDEPEND then.
+get_llvm_prefix() {
+	debug-print-function ${FUNCNAME} "${@}"
+
+	[[ ${#} -gt 1 ]] && die "Usage: ${FUNCNAME} [-b|-d]"
+
+	local prefix
+	case ${1--d} in
+		-d)
+			prefix=${ESYSROOT}
+			;;
+		-b)
+			prefix=${BROOT}
+			;;
+		*)
+			die "${FUNCNAME}: invalid option: ${1}"
+			;;
+	esac
+
+	echo "${prefix}/usr/lib/llvm/${LLVM_SLOT}"
+}
+
+# @FUNCTION: llvm-r1_pkg_setup
+# @DESCRIPTION:
+# Prepend the appropriate executable directory for the selected LLVM
+# slot to PATH.
+#
+# The PATH manipulation is only done for source builds. The function
+# is a no-op when installing a binary package.
+#
+# If any other behavior is desired, the contents of the function
+# should be inlined into the ebuild and modified as necessary.
+#
+# Note that this function is not exported if LLVM_OPTIONAL is set.
+# In that case, it needs to be called manually.
+llvm-r1_pkg_setup() {
+	debug-print-function ${FUNCNAME} "${@}"
+
+	if [[ ${MERGE_TYPE} != binary ]]; then
+		[[ -z ${LLVM_SLOT} ]] && die "LLVM_SLOT unset (broken USE_EXPAND?)"
+
+		llvm_fix_clang_version CC CPP CXX
+		# keep in sync with profiles/features/llvm/make.defaults!
+		llvm_fix_tool_path ADDR2LINE AR AS LD NM OBJCOPY OBJDUMP RANLIB
+		llvm_fix_tool_path READELF STRINGS STRIP
+
+		# Set LLVM_CONFIG to help Meson (bug #907965) but only do it
+		# for empty ESYSROOT (as a proxy for "are we cross-compiling?").
+		if [[ -z ${ESYSROOT} ]] ; then
+			llvm_fix_tool_path LLVM_CONFIG
+		fi
+
+		llvm_prepend_path "${LLVM_SLOT}"
+	fi
+}
+
+fi
+
+if [[ ! ${LLVM_OPTIONAL} ]]; then
+	EXPORT_FUNCTIONS pkg_setup
+fi