From 7c4d9364a25a1c2be8111221db08d4b3e691a6e5 Mon Sep 17 00:00:00 2001
From: lethosor <lethosor@gmail.com>
Date: Sun, 28 May 2023 02:51:06 -0400
Subject: [PATCH] Make allocator_fn compile for non-copy-assignable types like
 std::mutex

---
 library/include/DataDefs.h | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/library/include/DataDefs.h b/library/include/DataDefs.h
index 174156e76..7d840a9ad 100644
--- a/library/include/DataDefs.h
+++ b/library/include/DataDefs.h
@@ -497,11 +497,25 @@ namespace df
     using DFHack::DfLinkedList;
     using DFHack::DfOtherVectors;
 
+    template<class T>
+    typename std::enable_if<
+        std::is_copy_assignable<T>::value
+    >::type allocator_try_assign(void *out, const void *in) {
+        *(T*)out = *(const T*)in;
+    }
+
+    template<class T>
+    typename std::enable_if<
+        !std::is_copy_assignable<T>::value
+    >::type allocator_try_assign(void *out, const void *in) {
+        // assignment is not possible; do nothing
+    }
+
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wdelete-non-virtual-dtor"
     template<class T>
     void *allocator_fn(void *out, const void *in) {
-        if (out) { *(T*)out = *(const T*)in; return out; }
+        if (out) { allocator_try_assign<T>(out, in); return out; }
         else if (in) { delete (T*)in; return (T*)in; }
         else return new T();
     }