From c8ddfd5637f6d8e367e4fd3ef61a92d6dcd344e7 Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Wed, 28 Sep 2022 04:12:11 +0200
Subject: [PATCH] Fix C++ memory layout for the TempoMap

Usually C++ class instance has the same mem address as its first parent.
LuaBridge uses this to for derived classes. A TemopPoint instance has
the same address as its parent Tempo. However due to virtual inheritance
this was not the case due to a lack of virtual d'tor.

Now the following Lua code works correctly
```
tm = Temporal.TempoMap.read()
tp = Temporal.timepos_t (0)
print (tm:tempo_at(tp):note_type())
```

Previously the last line failed calling Tempo::note_type()
on a TempoPoint instance, due to memory offset e.g.
TempoPoint: 0x600000ff90e0 Tempo: 0x600000ff90e8
---
 libs/temporal/temporal/tempo.h | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/libs/temporal/temporal/tempo.h b/libs/temporal/temporal/tempo.h
index 8dd28c58f2..090da7ec0c 100644
--- a/libs/temporal/temporal/tempo.h
+++ b/libs/temporal/temporal/tempo.h
@@ -63,7 +63,7 @@ class TempoMap;
 class MapOwned {
  protected:
 	MapOwned (TempoMap const & map) : _map (&map) {}
-	~MapOwned () {}
+	virtual ~MapOwned () {}
 
  public:
 	TempoMap const & map() const { return *_map; }
@@ -174,6 +174,7 @@ class LIBTEMPORAL_API Tempo {
 	static std::string xml_node_name;
 
 	Tempo (XMLNode const &);
+	virtual ~Tempo () {}
 
 	/**
 	 * @param npm Note Types per minute
@@ -313,6 +314,8 @@ class LIBTEMPORAL_API Meter {
 	Meter (int8_t dpb, int8_t nv) : _note_value (nv), _divisions_per_bar (dpb) {}
 	Meter (Meter const & other) : _note_value (other._note_value), _divisions_per_bar (other._divisions_per_bar) {}
 
+	virtual ~Meter () {}
+
 	int divisions_per_bar () const { return _divisions_per_bar; }
 	int note_value() const { return _note_value; }
 
@@ -357,6 +360,8 @@ class /*LIBTEMPORAL_API*/ MeterPoint : public Meter, public meter_hook, public v
 	LIBTEMPORAL_API MeterPoint (TempoMap const & map, XMLNode const &);
 	LIBTEMPORAL_API MeterPoint (Meter const & m, Point const & p) : Point (p), Meter (m) {}
 
+	virtual ~MeterPoint () {}
+
 	LIBTEMPORAL_API Beats quarters_at (BBT_Time const & bbt) const;
 	LIBTEMPORAL_API BBT_Time bbt_at (Beats const & beats) const;
 
@@ -386,6 +391,8 @@ class /*LIBTEMPORAL_API*/ TempoPoint : public Tempo, public tempo_hook, public v
 	LIBTEMPORAL_API TempoPoint (Tempo const & t, Point const & p) : Point (p), Tempo (t), _omega (0.) {}
 	LIBTEMPORAL_API TempoPoint (TempoMap const & map, XMLNode const &);
 
+	virtual ~TempoPoint () {}
+
 	/* just change the tempo component, without moving */
 	LIBTEMPORAL_API TempoPoint& operator=(Tempo const & t) {
 		*((Tempo*)this) = t;
@@ -454,10 +461,11 @@ class /*LIBTEMPORAL_API*/ TempoPoint : public Tempo, public tempo_hook, public v
     computation code that requires both tempo and meter information every place
     it is used.
 */
-class LIBTEMPORAL_API TempoMetric {
+class LIBTEMPORAL_API TempoMetric
+{
   public:
 	TempoMetric (TempoPoint const & t, MeterPoint const & m) : _tempo (&t), _meter (&m) {}
-	~TempoMetric () {}
+	virtual ~TempoMetric () {}
 
 	TempoPoint const & tempo() const { return *_tempo; }
 	MeterPoint const & meter() const { return *_meter; }
@@ -538,6 +546,8 @@ class /*LIBTEMPORAL_API*/ MusicTimePoint :  public bartime_hook, public virtual
 
 	LIBTEMPORAL_API MusicTimePoint (TempoMap const & map, XMLNode const &);
 
+	virtual ~MusicTimePoint () {}
+
 	LIBTEMPORAL_API bool operator== (MusicTimePoint const & other) const {
 		return TempoPoint::operator== (other) && MeterPoint::operator== (other);
 	}