From 5c01167303f7baaec381a4a85ad5f4f3ca16c3c6 Mon Sep 17 00:00:00 2001
From: =?utf8?q?Micha=C5=82=20G=C3=B3rny?= <mgorny@gentoo.org>
Date: Fri, 10 Nov 2017 23:41:55 +0100
Subject: [PATCH] sys-devel/llvm: Add custom SOVERSION suffix when linking to
 libc++

---
 sys-devel/llvm/llvm-9999.ebuild | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/sys-devel/llvm/llvm-9999.ebuild b/sys-devel/llvm/llvm-9999.ebuild
index 612f8a07e7b8..d5404d204a07 100644
--- a/sys-devel/llvm/llvm-9999.ebuild
+++ b/sys-devel/llvm/llvm-9999.ebuild
@@ -89,6 +89,18 @@ src_prepare() {
 	cmake-utils_src_prepare
 }
 
+# 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* ]]
+}
+
 multilib_src_configure() {
 	local ffi_cflags ffi_ldflags
 	if use libffi; then
@@ -132,6 +144,15 @@ multilib_src_configure() {
 		-DOCAMLFIND=NO
 	)
 
+	if is_libcxx_linked; then
+		# Smart hack: alter version suffix -> SOVERSION when linking
+		# against libc++. This way we won't end up mixing LLVM libc++
+		# libraries with libstdc++ clang, and the other way around.
+		mycmakeargs+=(
+			-DLLVM_VERSION_SUFFIX="libcxx"
+		)
+	fi
+
 #	Note: go bindings have no CMake rules at the moment
 #	but let's kill the check in case they are introduced
 #	if ! multilib_is_native_abi || ! use go; then
-- 
2.26.2