[gentoo-dev] [PATCH 1/2] llvm.eclass: Fix CC/CXX version to prevent the eclass overriding it

[Michał Górny]

Fix the clang executable in CC, CPP and CXX variables to include
the version number, in order to prevent the PATH manipulations done
by llvm.eclass from overriding the compiler.  Otherwise, a package
requiring older LLVM libraries could cause an older compiler version
being used, effectively resulting in a system built by mixed set
of clang versions.

Signed-off-by: Michał Górny <mgorny@g.o>
---
 eclass/llvm.eclass | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/eclass/llvm.eclass b/eclass/llvm.eclass
index 1effcc555905..39299d06dbe9 100644
--- a/eclass/llvm.eclass
+++ b/eclass/llvm.eclass
@@ -180,6 +180,40 @@ get_llvm_prefix() {
 	die "No LLVM slot${1:+ <= ${1}} satisfying the package's dependencies found installed!"
 }
 
+# @FUNCTION: llvm_fix_clang_version
+# @USAGE: <variable-name>...
+# @DESCRIPTION:
+# Fix the clang compiler name in specified variables to include
+# the major version, to prevent PATH alterations from forcing an older
+# clang version being used.
+llvm_fix_clang_version() {
+	debug-print-function ${FUNCNAME} "${@}"
+
+	local shopt_save=$(shopt -p -o noglob)
+	set -f
+	local var
+	for var; do
+		local split=( ${!var} )
+		case ${split[0]} in
+			*clang|*clang++|*clang-cpp)
+				local version=()
+				read -r -a version < <("${split[0]}" --version)
+				local major=${version[-1]%%.*}
+				if [[ -n ${major//[0-9]} ]]; then
+					die "${var}=${!var} produced invalid --version: ${version[*]}"
+				fi
+
+				split[0]+=-${major}
+				if ! type -P "${split[0]}" &>/dev/null; then
+					die "${split[0]} does not seem to exist"
+				fi
+				declare -g "${var}=${split[*]}"
+				;;
+		esac
+	done
+	${shopt_save}
+}
+
 # @FUNCTION: llvm_pkg_setup
 # @DESCRIPTION:
 # Prepend the appropriate executable directory for the newest
@@ -198,6 +232,8 @@ llvm_pkg_setup() {
 	debug-print-function ${FUNCNAME} "${@}"
 
 	if [[ ${MERGE_TYPE} != binary ]]; then
+		llvm_fix_clang_version CC CPP CXX
+
 		local llvm_path=$(get_llvm_prefix "${LLVM_MAX_SLOT}")/bin
 		local IFS=:
 		local split_path=( ${PATH} )
-- 
2.38.0