Symbol visibility tests

include/VersionedMap.h

@@ -37,7 +37,7 @@ namespace weaselab {
  *   - Methods that make stronger guarantees about the safety of calling
  * concurrently with non-const methods are documented as such.
  */
-struct VersionedMap {
+struct __attribute__((__visibility__("default"))) VersionedMap {
 
   /** Indicates how `Mutation::param1` and `Mutation::param2` are to be
    * interpreted. */