Free allocated memory in unpack_action_data

contracts/eosiolib/action.hpp

@@ -48,9 +48,15 @@ namespace eosio {
    T unpack_action_data() {
       constexpr size_t max_stack_buffer_size = 512;
       size_t size = action_data_size();
-      char* buffer = (char*)( max_stack_buffer_size < size ? malloc(size) : alloca(size) );
+      const bool heap_allocation = max_stack_buffer_size < size;
+      char* buffer = (char*)( heap_allocation ? malloc(size) : alloca(size) );
       read_action_data( buffer, size );
-      return unpack<T>( buffer, size );
+      auto res = unpack<T>( buffer, size );
+      // Free allocated memory 
+      if ( heap_allocation ) {
+         free(buffer);
+      }
+      return res;
    }
 
    using ::require_auth;