Make lib work as a c or c++ library

ConflictSet.cpp

@@ -594,7 +594,7 @@ bool checkInvariants(Node *node) {
 
 } // namespace
 
-struct ConflictSet::Impl {
+struct __attribute__((__visibility__("hidden"))) ConflictSet::Impl {
   Node *root;
   int64_t oldestVersion;
   explicit Impl(int64_t oldestVersion) noexcept
@@ -772,8 +772,10 @@ ConflictSet::ConflictSet(int64_t oldestVersion)
     : impl(new(malloc(sizeof(Impl))) Impl{oldestVersion}) {}
 
 ConflictSet::~ConflictSet() {
-  impl->~Impl();
-  free(impl);
+  if (impl) {
+    impl->~Impl();
+    free(impl);
+  }
 }
 
 ConflictSet::ConflictSet(ConflictSet &&other) noexcept
@@ -784,6 +786,38 @@ ConflictSet &ConflictSet::operator=(ConflictSet &&other) noexcept {
   return *this;
 }
 
+using ConflictSet_Result = ConflictSet::Result;
+using ConflictSet_Key = ConflictSet::Key;
+using ConflictSet_ReadRange = ConflictSet::ReadRange;
+using ConflictSet_WriteRange = ConflictSet::WriteRange;
+
+extern "C" {
+__attribute__((__visibility__("default"))) void
+ConflictSet_check(void *cs, const ConflictSet_ReadRange *reads,
+                  ConflictSet_Result *results, int count) {
+  ((ConflictSet::Impl *)cs)->check(reads, results, count);
+}
+__attribute__((__visibility__("default"))) void
+ConflictSet_addWrites(void *cs, const ConflictSet_WriteRange *writes,
+                      int count) {
+  ((ConflictSet::Impl *)cs)->addWrites(writes, count);
+}
+__attribute__((__visibility__("default"))) void
+ConflictSet_setOldestVersion(void *cs, int64_t oldestVersion) {
+  ((ConflictSet::Impl *)cs)->setOldestVersion(oldestVersion);
+}
+__attribute__((__visibility__("default"))) void *
+ConflictSet_create(int64_t oldestVersion) {
+  return new (malloc(sizeof(ConflictSet::Impl)))
+      ConflictSet::Impl{oldestVersion};
+}
+__attribute__((__visibility__("default"))) void ConflictSet_destroy(void *cs) {
+  using Impl = ConflictSet::Impl;
+  ((Impl *)cs)->~Impl();
+  free(cs);
+}
+}
+
 #ifdef ENABLE_TESTS
 int main(void) {
   int64_t writeVersion = 0;