From 41808111aa0a58708daf66b2322940d4353e37d8 Mon Sep 17 00:00:00 2001
From: David Chisnall <theraven@FreeBSD.org>
Date: Sat, 5 Sep 2020 11:39:39 +0100
Subject: [PATCH] Fix compiling with libc++ but not linking with libc++.

---
 arc.mm | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arc.mm b/arc.mm
index c96681f..4530a64 100644
--- a/arc.mm
+++ b/arc.mm
@@ -110,6 +110,18 @@ static inline T* new_zeroed()
 	return static_cast<T*>(calloc(sizeof(T), 1));
 }
 
+#ifdef _LIBCPP_BEGIN_NAMESPACE_STD
+_LIBCPP_BEGIN_NAMESPACE_STD
+/**
+ * If we're compiling with libc++, we need to instantiate the vector base class
+ * to avoid linker errors.  Libc++ defines the functions that throw exceptions
+ * in the headers but makes them extern templates to avoid code duplication in
+ * the slow paths.
+ */
+template class __attribute__((visibility("hidden")))  __vector_base_common<true>;
+_LIBCPP_END_NAMESPACE_STD
+#endif
+
 
 static inline struct arc_tls* getARCThreadData(void)
 {