Prevent possible dangling pointers to Project from Clipboard

src/Clipboard.cpp

@@ -34,7 +34,7 @@ void Clipboard::Clear()
 {
    mT0 = 0.0;
    mT1 = 0.0;
-   mProject = nullptr;
+   mProject.reset();
    mTracks->Clear();
 
    // Emit an event for listeners
@@ -42,7 +42,7 @@ void Clipboard::Clear()
 }
 
 void Clipboard::Assign( TrackList && newContents,
-   double t0, double t1, AudacityProject *pProject )
+   double t0, double t1, const std::weak_ptr<AudacityProject> &pProject )
 {
    newContents.Swap( *mTracks );
    newContents.Clear();

src/Clipboard.h

@@ -35,20 +35,20 @@ public:
    double T1() const { return mT1; }
    double Duration() const { return mT1 - mT0; }
 
-   AudacityProject *Project() const { return mProject; }
+   const std::weak_ptr<AudacityProject> &Project() const { return mProject; }
 
    void Clear();
    
    void Assign(
      TrackList && newContents, double t0, double t1,
-     AudacityProject *pProject );
+     const std::weak_ptr<AudacityProject> &pProject );
 
 private:
    Clipboard();
    ~Clipboard();
 
    std::shared_ptr<TrackList> mTracks;
-   AudacityProject *mProject{};
+   std::weak_ptr<AudacityProject> mProject{};
    double mT0{ 0 };
    double mT1{ 0 };
 };

src/Project.h

@@ -103,6 +103,7 @@ class AUDACITY_DLL_API AudacityProject final
    : public wxEvtHandler
    , public AttachedObjects
    , public AttachedWindows
+   , public std::enable_shared_from_this<AudacityProject>
 {
  public:
    using AttachedObjects = ::AttachedObjects;

src/menus/EditMenus.cpp

@@ -85,6 +85,7 @@ bool DoPasteNothingSelected(AudacityProject &project)
    else
    {
       const auto &clipboard = Clipboard::Get();
+      auto clipboardProject = clipboard.Project().lock();
       auto clipTrackRange = clipboard.GetTracks().Any< const Track >();
       if (clipTrackRange.empty())
          return true; // nothing to paste
@@ -97,7 +98,7 @@ bool DoPasteNothingSelected(AudacityProject &project)
          Track *pNewTrack;
          pClip->TypeSwitch(
             [&](const WaveTrack *wc) {
-               if ((clipboard.Project() != &project))
+               if ((clipboardProject.get() != &project))
                   // Cause duplication of block files on disk, when copy is
                   // between projects
                   locker.emplace(wc);
@@ -277,7 +278,7 @@ void OnCut(const CommandContext &context)
        std::move( newClipboard ),
        selectedRegion.t0(),
        selectedRegion.t1(),
-       &project
+       project.shared_from_this()
    );
 
    // Proceed to change the project.  If this throws, the project will be
@@ -369,7 +370,7 @@ void OnCopy(const CommandContext &context)
 
    // Survived possibility of exceptions.  Commit changes to the clipboard now.
    clipboard.Assign( std::move( newClipboard ),
-      selectedRegion.t0(), selectedRegion.t1(), &project );
+      selectedRegion.t0(), selectedRegion.t1(), project.shared_from_this() );
 
    //Make sure the menus/toolbar states get updated
    trackPanel.Refresh(false);
@@ -415,6 +416,7 @@ void OnPaste(const CommandContext &context)
 
    auto pC = clipTrackRange.begin();
    size_t nnChannels=0, ncChannels=0;
+   auto clipboardProject = clipboard.Project().lock();
    while (*pN && *pC) {
       auto n = *pN;
       auto c = *pC;
@@ -507,7 +509,7 @@ void OnPaste(const CommandContext &context)
          n->TypeSwitch(
             [&](WaveTrack *wn){
                const auto wc = static_cast<const WaveTrack *>(c);
-               if (clipboard.Project() != &project)
+               if (clipboardProject.get() != &project)
                   // Cause duplication of block files on disk, when copy is
                   // between projects
                   locker.emplace(wc);
@@ -581,7 +583,7 @@ void OnPaste(const CommandContext &context)
       const auto wc =
          *clipboard.GetTracks().Any< const WaveTrack >().rbegin();
       Optional<WaveTrack::Locker> locker;
-      if (clipboard.Project() != &project && wc)
+      if (clipboardProject.get() != &project && wc)
          // Cause duplication of block files on disk, when copy is
          // between projects
          locker.emplace(static_cast<const WaveTrack*>(wc));
@@ -702,7 +704,7 @@ void OnSplitCut(const CommandContext &context)
 
    // Survived possibility of exceptions.  Commit changes to the clipboard now.
    clipboard.Assign( std::move( newClipboard ),
-      selectedRegion.t0(), selectedRegion.t1(), &project );
+      selectedRegion.t0(), selectedRegion.t1(), project.shared_from_this() );
 
    ProjectHistory::Get( project )
       .PushState(XO("Split-cut to the clipboard"), XO("Split Cut"));

src/menus/LabelMenus.cpp

@@ -4,6 +4,7 @@
 #include "../LabelTrack.h"
 #include "../Menus.h"
 #include "../Prefs.h"
+#include "../Project.h"
 #include "../ProjectAudioIO.h"
 #include "../ProjectHistory.h"
 #include "../ProjectWindow.h"
@@ -266,7 +267,7 @@ void EditClipboardByLabel( AudacityProject &project,
 
    // Survived possibility of exceptions.  Commit changes to the clipboard now.
    clipboard.Assign( std::move( newClipboard ),
-      regions.front().start, regions.back().end, &project );
+      regions.front().start, regions.back().end, project.shared_from_this() );
 }
 
 }