From 0c4514efb0788e5f19913802e1aa011cfcc24321 Mon Sep 17 00:00:00 2001
From: Paul Licameli <paul.licameli@audacityteam.org>
Date: Wed, 26 Aug 2020 16:01:54 -0400
Subject: [PATCH] Avoid some unexpected recursions because of yields to event
 loop...

... See code comments.

Not proved to be a cause of data loss bugs, but they caused surprises when
trying to step in the debugger.
---
 src/ProjectAudioManager.cpp | 13 +++++++++----
 src/SqliteSampleBlock.cpp   |  9 +++++++++
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/src/ProjectAudioManager.cpp b/src/ProjectAudioManager.cpp
index a4cb83fca..148e4db5a 100644
--- a/src/ProjectAudioManager.cpp
+++ b/src/ProjectAudioManager.cpp
@@ -910,16 +910,21 @@ void ProjectAudioManager::OnAudioIOStopRecording()
 
             history.ModifyState( true ); // this might fail and throw
 
-            ShowWarningDialog(&window, wxT("DropoutDetected"), XO("\
+            // CallAfter so that we avoid any problems of yielding
+            // to the event loop while still inside the timer callback,
+            // entering StopStream() recursively
+            wxTheApp->CallAfter( [&] {
+               ShowWarningDialog(&window, wxT("DropoutDetected"), XO("\
 Recorded audio was lost at the labeled locations. Possible causes:\n\
 \n\
 Other applications are competing with Audacity for processor time\n\
 \n\
 You are saving directly to a slow external storage device\n\
 "
-               ),
-               false,
-               XXO("Turn off dropout detection"));
+                  ),
+                  false,
+                  XXO("Turn off dropout detection"));
+            });
          }
       }
    }
diff --git a/src/SqliteSampleBlock.cpp b/src/SqliteSampleBlock.cpp
index 589d7df51..39e51df55 100644
--- a/src/SqliteSampleBlock.cpp
+++ b/src/SqliteSampleBlock.cpp
@@ -268,6 +268,15 @@ SqliteSampleBlock::SqliteSampleBlock(
 
 SqliteSampleBlock::~SqliteSampleBlock()
 {
+   if (mBlockID == 0) {
+      // The block object was constructed but failed to Load() or Commit().
+      // Just let the stack unwind.  Don't violate the assertion in
+      // Delete(), which may do odd recursive things in debug builds when it
+      // yields to the UI to put up a dialog, but then dispatches timer
+      // events that try again to finish recording.
+      return;
+   }
+
    // See ProjectFileIO::Bypass() for a description of mIO.mBypass
    if (!mLocked && !Conn()->ShouldBypass())
    {