From be86cbbe4eff931db0e59ce14fdba19365c075f7 Mon Sep 17 00:00:00 2001
From: Antoine C <mixxx@acolombier.dev>
Date: Tue, 8 Oct 2024 22:33:38 +0100
Subject: [PATCH] fix: prevent null CO access when cloning sampler or preview

---
 src/engine/channels/enginechannel.h |  2 +-
 src/engine/channels/enginedeck.cpp  | 11 +++++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/src/engine/channels/enginechannel.h b/src/engine/channels/enginechannel.h
index ef29eca9e0c..6598059c352 100644
--- a/src/engine/channels/enginechannel.h
+++ b/src/engine/channels/enginechannel.h
@@ -53,7 +53,7 @@ class EngineChannel : public EngineObject {
     void setTalkover(bool enabled);
     virtual bool isTalkoverEnabled() const;
     inline bool isTalkoverChannel() { return m_bIsTalkoverChannel; };
-    inline bool isPrimaryDeck() {
+    inline bool isPrimaryDeck() const {
         return m_bIsPrimaryDeck;
     };
     int getChannelIndex() {
diff --git a/src/engine/channels/enginedeck.cpp b/src/engine/channels/enginedeck.cpp
index 25e02a674c7..a5a6f0cd277 100644
--- a/src/engine/channels/enginedeck.cpp
+++ b/src/engine/channels/enginedeck.cpp
@@ -10,6 +10,7 @@
 #include "engine/enginevumeter.h"
 #include "moc_enginedeck.cpp"
 #include "track/track.h"
+#include "util/assert.h"
 #include "util/sample.h"
 
 #ifdef __STEM__
@@ -206,6 +207,16 @@ void EngineDeck::cloneStemState(const EngineDeck* deckToClone) {
     VERIFY_OR_DEBUG_ASSERT(deckToClone) {
         return;
     }
+    // Sampler and preview decks don't have stem controls
+    if (!isPrimaryDeck() || !deckToClone->isPrimaryDeck()) {
+        return;
+    }
+    VERIFY_OR_DEBUG_ASSERT(m_stemGain.size() == kMaxSupportedStems &&
+            m_stemMute.size() == kMaxSupportedStems &&
+            deckToClone->m_stemGain.size() == kMaxSupportedStems &&
+            deckToClone->m_stemMute.size() == kMaxSupportedStems) {
+        return;
+    }
     for (int stemIdx = 0; stemIdx < kMaxSupportedStems; stemIdx++) {
         m_stemGain[stemIdx]->set(deckToClone->m_stemGain[stemIdx]->get());
         m_stemMute[stemIdx]->set(deckToClone->m_stemMute[stemIdx]->get());