From 1fe30e79c368ce71e024d70c3ec07a6aed3ef262 Mon Sep 17 00:00:00 2001
From: Michael Haubenwallner <haubi@gentoo.org>
Date: Fri, 22 Mar 2019 17:52:05 +0100
Subject: [PATCH] from FEATURES=stacked-prefix to USE=prefix-stack

Rather than telling the base prefix' portage to support stacked prefix,
be explicit in the stacked prefix about to USE that feature.
Bug: https://bugs.gentoo.org/658572
---
 bin/install-qa-check.d/05prefix | 10 +++-------
 bin/phase-helpers.sh            | 12 ++++--------
 lib/portage/const.py            |  1 -
 3 files changed, 7 insertions(+), 16 deletions(-)

diff --git a/bin/install-qa-check.d/05prefix b/bin/install-qa-check.d/05prefix
index 03da3bbce..4f48e4216 100644
--- a/bin/install-qa-check.d/05prefix
+++ b/bin/install-qa-check.d/05prefix
@@ -36,16 +36,12 @@ install_qa_check_prefix() {
 	local WHITELIST=" /usr/bin/env "
 	# shebang can be an absolutised path, bug #342929
 	local eprefix=$(canonicalize ${EPREFIX})
-	# Without the stacked-prefix feature, tests using BPREFIX
-	# are redundant to EPREFIX, but run only if we will fail.
+	# Without USE=prefix-stack, tests using BPREFIX are
+	# redundant to EPREFIX, but run only if we will fail.
 	# Otherways, BPREFIX really is BROOT (the EAPI 7 one).
 	local BPREFIX=${EPREFIX}
 	local bprefix=${eprefix}
-	if has stacked-prefix ${FEATURES} &&
-	   [[ -z ${ROOT%/} ]]             &&
-	   [[ ${CBUILD} == ${CHOST} ]]    &&
-	   [[ ${EPREFIX} != ${BROOT-${PORTAGE_OVERRIDE_EPREFIX}} ]] &&
-	:; then
+	if has prefix-stack ${USE} ; then
 		BPREFIX=${BROOT-${PORTAGE_OVERRIDE_EPREFIX}}
 		bprefix=$(canonicalize ${BPREFIX})
 	fi
diff --git a/bin/phase-helpers.sh b/bin/phase-helpers.sh
index 606b1cdfd..c64f1106b 100644
--- a/bin/phase-helpers.sh
+++ b/bin/phase-helpers.sh
@@ -932,18 +932,14 @@ ___best_version_and_has_version_common() {
 			fi ;;
 	esac
 
-	# PREFIX LOCAL: stacked-prefix feature
+	# PREFIX LOCAL: prefix-stack feature
 	if ___eapi_has_prefix_variables         &&
 	   has "${root_arg}" '--host-root' '-b' &&
-	   has stacked-prefix ${FEATURES}       &&
+	   has prefix-stack ${USE}              &&
 	   [[ -z ${ROOT%/} ]]                   &&
-	   [[ ${CBUILD} == ${CHOST} ]]          &&
-	   [[ ${EPREFIX} != ${BROOT-${PORTAGE_OVERRIDE_EPREFIX}} ]] &&
 	:; then
-		# When we merge into another EPREFIX, but not into some ROOT,
-		# and CHOST is equal to CBUILD, build tools found in EPREFIX
-		# perfectly work for the current build environment.
-		# In a "stacked prefix" we explicitly utilize this situation.
+		# When we merge into "stacked" EPREFIX, but not into some ROOT, build
+		# tools found in EPREFIX perfectly work for current build environment.
 		"${FUNCNAME[1]}" "${atom}" && return 0
 	fi
 	# END PREFIX LOCAL
diff --git a/lib/portage/const.py b/lib/portage/const.py
index eddce377d..db02cbc56 100644
--- a/lib/portage/const.py
+++ b/lib/portage/const.py
@@ -207,7 +207,6 @@ SUPPORTED_FEATURES       = frozenset([
 	"splitdebug",
 	"split-elog",
 	"split-log",
-	"stacked-prefix",  # PREFIX LOCAL
 	"strict",
 	"strict-keepdir",
 	"stricter",
-- 
2.19.2