Fix a few bugs with GC roots

src/arena.hpp

@@ -1,6 +1,7 @@
 #pragma once
 
 #include <concepts>
+#include <iostream>
 
 #include "error.hpp"
 #include "pod.hpp"
@@ -58,10 +59,10 @@ class GcRootList {
   }
 
   void remove() {
-    _prev = 0;
-    _next = 0;
     if (_prev) _prev->_next = _next;
     if (_next) _next->_prev = _prev;
+    _prev = 0;
+    _next = 0;
   }
 
   GcRootList* next() { return _next; }
@@ -161,4 +162,5 @@ GcRoot<T>::GcRoot(GcRoot<T>&& rhs) {
   rhs._node->update(this);
   _ptr = rhs._ptr;
   _node = rhs._node;
+  rhs._node = 0;
 }

src/common.hpp

@@ -96,10 +96,28 @@ class String : public Object {
     auto pod_string = TRY(arena.alloc<PodString>(size * sizeof(char32_t)));
 
     memcpy(pod_string->data, chars, size * sizeof(char32_t));
+    pod_string->size = size;
 
     return String(TRY(MkGcRoot(pod_string, arena)));
   }
 
+  static Result<String> create(Arena& arena, const char* str) {
+    uint64_t size = strlen(str);
+    auto pod_string = TRY(arena.alloc<PodString>(size * sizeof(char32_t)));
+
+    for (uint64_t i = 0; i < size; i++) pod_string->data[i] = str[i];
+    pod_string->size = size;
+
+    return String(TRY(MkGcRoot(pod_string, arena)));
+  }
+
+  uint64_t size() { return _value->size; }
+
+  Result<char32_t> operator[](uint64_t idx) {
+    if (idx >= _value->size) return ErrorCode::IndexOutOfRange;
+    return _value->data[idx];
+  }
+
   virtual Result<Value> copy(Arena& arena) final;
 
  private:
@@ -204,7 +222,10 @@ class Value {
  public:
   Value() { new (buf) Nil(); }
   ~Value() { ((Object*)buf)->~Object(); }
-  Value(Value&& val) { memcpy(buf, val.buf, 24); }
+  Value(Value&& val) {
+    memcpy(buf, val.buf, 24);
+    new (val.buf) Nil();
+  }
   Value(const Value&) = delete;
 
   template <class T>

src/error.hpp

@@ -2,6 +2,7 @@
 
 enum class ErrorCode {
   Success,
-  OutOfMemory
+  OutOfMemory,
+  IndexOutOfRange
 
 };

src/vli.cpp

@@ -18,8 +18,13 @@ int main() {
   std::cout << int(((Int64&)*val).value()) << "\n";
   */
 
-  auto lst = DIEIF(arena.alloc<PodPair>());
-  auto root = DIEIF(MkGcRoot(lst, arena));
+  {
+    auto s = DIEIF(String::create(arena, "foo"));
+
+    std::cout << "roout count: " << arena.root_count() << "\n";
+    std::cout << "char: " << (char)DIEIF(s[2]) << "\n";
+  }
+  std::cout << "roout count: " << arena.root_count() << "\n";
 
   return 0;
 }