Free strdup'ed string space.

gc.c

@@ -256,6 +256,25 @@ static void add_to_free_list(void *p)
     free_list = ch;
 }
 
+static void free_val(Value v)
+{
+    if (value_is_immediate(v) || v == Qnil)
+        return;
+    switch (VALUE_TAG(v)) {
+    case TAG_STR: {
+        String *p = STRING(v);
+        free((char *) p->body);
+        return;
+    }
+    case TAG_PAIR:
+    case TAG_CLOSURE:
+    case TAG_CONTINUATION:
+    case TAG_CFUNC:
+    case TAG_SYNTAX:
+        return;
+    }
+}
+
 static void sweep(void)
 {
     static Header dummy = { .size = 0, .allocated = true, .living = false };
@@ -268,6 +287,7 @@ static void sweep(void)
             h->living = false;
             prev = h;
         } else if (h->allocated) {
+            free_val((Value)(h+1));
             if (!prev->allocated)
                 prev->size += offset;
             else {