Merge pull request 'Disallow copying ConflictSet in C++98/C++03' (#51) from weaselbot/conflict-set:weaselbot/issue-48 into main

Reviewed-on: weaselab/conflict-set#51

include/ConflictSet.h

@@ -132,6 +132,13 @@ struct __attribute__((__visibility__("default"))) ConflictSet {
 
 private:
   Impl *impl;
+#if __cplusplus <= 199711L
+  /* Declared private and left undefined to prevent copying in C++98/C++03.
+     The compiler would otherwise implicitly generate public copy operations,
+     which share the opaque Impl* and cause a double-free. */
+  ConflictSet(const ConflictSet &);
+  ConflictSet &operator=(const ConflictSet &);
+#endif
 };
 } /* namespace weaselab */