From 3b260e7d1bd9bda1fb1138b27d7994a61898e61e Mon Sep 17 00:00:00 2001
From: Georgy Yakovlev <gyakovlev@gentoo.org>
Date: Thu, 6 Oct 2022 14:32:11 -0700
Subject: [PATCH] dev-lang/rust: change libcxx detection method

Bug: https://bugs.gentoo.org/732632
Bug: https://bugs.gentoo.org/875563
Signed-off-by: Georgy Yakovlev <gyakovlev@gentoo.org>
---
 dev-lang/rust/rust-1.64.0-r1.ebuild | 24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/dev-lang/rust/rust-1.64.0-r1.ebuild b/dev-lang/rust/rust-1.64.0-r1.ebuild
index 436894d9af8..4ab6f6c152f 100644
--- a/dev-lang/rust/rust-1.64.0-r1.ebuild
+++ b/dev-lang/rust/rust-1.64.0-r1.ebuild
@@ -231,6 +231,17 @@ llvm_check_deps() {
 	has_version -r "sys-devel/llvm:${LLVM_SLOT}[${LLVM_TARGET_USEDEPS// /,}]"
 }
 
+# Is LLVM being linked against libc++?
+is_libcxx_linked() {
+	local code='#include <ciso646>
+#if defined(_LIBCPP_VERSION)
+	HAVE_LIBCXX
+#endif
+'
+	local out=$($(tc-getCXX) ${CXXFLAGS} ${CPPFLAGS} -x c++ -E -P - <<<"${code}") || return 1
+	[[ ${out} == *HAVE_LIBCXX* ]]
+}
+
 pkg_pretend() {
 	pre_build_checks
 }
@@ -297,7 +308,7 @@ src_prepare() {
 src_configure() {
 	filter-flags '-flto*' # https://bugs.gentoo.org/862109 https://bugs.gentoo.org/866231
 
-	local rust_target="" rust_targets="" arch_cflags use_libcxx="false"
+	local rust_target="" rust_targets="" arch_cflags
 
 	# Collect rust target names to compile standard libs for all ABIs.
 	for v in $(multilib_get_enabled_abi_pairs); do
@@ -335,14 +346,6 @@ src_configure() {
 
 	rust_target="$(rust_abi)"
 
-	# https://bugs.gentoo.org/732632
-	if tc-is-clang; then
-		local clang_slot="$(clang-major-version)"
-		if { has_version "sys-devel/clang:${clang_slot}[default-libcxx(-)]" || has_version "sys-devel/clang-common:${clang_slot}[default-libcxx(-)]" || is-flagq -stdlib=libc++; }; then
-			use_libcxx="true"
-		fi
-	fi
-
 	local cm_btype="$(usex debug DEBUG RELEASE)"
 	cat <<- _EOF_ > "${S}"/config.toml
 		changelog-seen = 2
@@ -355,7 +358,8 @@ src_configure() {
 		targets = "${LLVM_TARGETS// /;}"
 		experimental-targets = ""
 		link-shared = $(toml_usex system-llvm)
-		$(if [[ ${use_libcxx} == true ]]; then
+		$(if is_libcxx_linked; then
+			# https://bugs.gentoo.org/732632
 			echo "use-libcxx = true"
 			echo "static-libstdcpp = false"
 		fi)
-- 
2.38.0