Remove ostream from class StreamBuffer

luprex/cpp/core/drivenengine.hpp

@@ -204,7 +204,7 @@ public:
 
     // Obtain the output buffer of the stdio channel as an ostream.
     //
-    std::ostream &stdostream() { return get_stdio_channel()->out()->ostream(); }
+    std::ostream &stdostream() { return *stdostream_; }
 
     // Set the prompt for the console.
     //
@@ -305,6 +305,7 @@ private:
     SharedChannel channels_[DRV_MAX_CHAN];
     int next_unused_chid_;
     SharedChannel stdio_channel_;
+    std::unique_ptr<std::ostream> stdostream_;
     eng::vector<SharedChannel> accepted_channels_;
     eng::vector<uint32_t> new_outgoing_;
     util::LuaSourcePtr lua_source_;