From 887d270a8327da46a89d8e5375f172db778f0ff9 Mon Sep 17 00:00:00 2001
From: "Matthias P. Braendli" <matthias.braendli@mpb.li>
Date: Sat, 25 Mar 2017 18:21:12 +0100
Subject: Fix race condition for PipelinedModCodec thread startup

The thread could start before the vtable containing the subclass function is ready, leading
to a crash because the thread calls a pure virtual function.
---
 src/FIRFilter.cpp   |  2 ++
 src/FIRFilter.h     |  2 +-
 src/GainControl.cpp |  2 ++
 src/ModPlugin.cpp   | 10 ++++++++--
 src/ModPlugin.h     |  9 +++++++--
 5 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/src/FIRFilter.cpp b/src/FIRFilter.cpp
index 0e85e0f..4296822 100644
--- a/src/FIRFilter.cpp
+++ b/src/FIRFilter.cpp
@@ -83,6 +83,8 @@ FIRFilter::FIRFilter(const std::string& taps_file) :
     RC_ADD_PARAMETER(tapsfile, "Filename containing filter taps. When written to, the new file gets automatically loaded.");
 
     load_filter_taps(m_taps_file);
+
+    start_pipeline_thread();
 }
 
 void FIRFilter::load_filter_taps(const std::string &tapsFile)
diff --git a/src/FIRFilter.h b/src/FIRFilter.h
index 1fe0004..fb6b4d6 100644
--- a/src/FIRFilter.h
+++ b/src/FIRFilter.h
@@ -65,7 +65,7 @@ public:
 
 
 protected:
-    int internal_process(Buffer* const dataIn, Buffer* dataOut);
+    virtual int internal_process(Buffer* const dataIn, Buffer* dataOut);
     void load_filter_taps(const std::string &tapsFile);
 
     std::string m_taps_file;
diff --git a/src/GainControl.cpp b/src/GainControl.cpp
index 9eb1678..f363d20 100644
--- a/src/GainControl.cpp
+++ b/src/GainControl.cpp
@@ -69,6 +69,8 @@ GainControl::GainControl(size_t framesize,
     RC_ADD_PARAMETER(digital, "Digital Gain");
     RC_ADD_PARAMETER(mode, "Gainmode (fix|max|var)");
     RC_ADD_PARAMETER(var, "Variance setting for gainmode var (default: 4)");
+
+    start_pipeline_thread();
 }
 
 GainControl::~GainControl()
diff --git a/src/ModPlugin.cpp b/src/ModPlugin.cpp
index 34ad797..74db5f9 100644
--- a/src/ModPlugin.cpp
+++ b/src/ModPlugin.cpp
@@ -74,10 +74,11 @@ int ModOutput::process(
 
 PipelinedModCodec::PipelinedModCodec() :
     ModCodec(),
+    m_number_of_runs(0),
     m_input_queue(),
     m_output_queue(),
-    m_number_of_runs(0),
-    m_thread(&PipelinedModCodec::process_thread, this)
+    m_running(false),
+    m_thread()
 {
 }
 
@@ -89,6 +90,11 @@ PipelinedModCodec::~PipelinedModCodec()
     }
 }
 
+void PipelinedModCodec::start_pipeline_thread()
+{
+    m_thread = std::thread(&PipelinedModCodec::process_thread, this);
+}
+
 int PipelinedModCodec::process(Buffer* dataIn, Buffer* dataOut)
 {
     if (!m_running) {
diff --git a/src/ModPlugin.h b/src/ModPlugin.h
index f3a8e2a..d3aa780 100644
--- a/src/ModPlugin.h
+++ b/src/ModPlugin.h
@@ -83,15 +83,20 @@ public:
     virtual const char* name() = 0;
 
 protected:
-    void process_thread(void);
+    // Once the instance implementing PipelinedModCodec has been constructed,
+    // it must call start_pipeline_thread()
+    void start_pipeline_thread(void);
     virtual int internal_process(Buffer* const dataIn, Buffer* dataOut) = 0;
 
+private:
+    size_t m_number_of_runs;
+
     ThreadsafeQueue<std::shared_ptr<Buffer> > m_input_queue;
     ThreadsafeQueue<std::shared_ptr<Buffer> > m_output_queue;
 
     std::atomic<bool> m_running;
-    size_t m_number_of_runs;
     std::thread m_thread;
+    void process_thread(void);
 };
 
 
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