Using A C++ Class In Windows Form Leads to System.AccessViolationException - c++

Question

I have written a few C++ classes which employ a variety C++ libraries. I made a Windows Form project, and set it up to use my classes successfully. However, I recently made another C++ class and now I consistently get:
A first chance exception of type 'System.AccessViolationException' occurred in TEST_OCU.exe
which leads to:
An unhandled exception of type 'System.TypeInitializationException' occurred in Unknown Module.
Additional information: The type initializer for '<Module>' threw an exception.
The program hasn't even started running yet, and the new, problem-causing C++ class hasn't even been constructed yet. If I comment out the new call, and only have a pointer to this new C++ class, everything compiles just fine. BUT, if somewhere I do something like:
if(new_class_ptr != NULL)
new_class_ptr->SomeFunction() //It doesn't matter what function this is
This will throw those violations again
Some facts:
Compiling and linking is fine, this seems to be a run-time problem.
My solution employs unmanaged C++ libraries and classes (that I have written), and one managed C++ Form.
So far I haven't had any problems, I've used a few C++ libraries successfully for a while. This is caused by a new C++ class I recently wrote.
The C++ class which causes these violations uses std::ifstream to read in a file. If I comment out the std::ifstream input_file(filename); my Forms project runs successfully.
If I use the C++ class in a simple Win32 project, it compiles and runs just fine with the std::ifstream.
I have a strong feeling it is related to this question
Could anyone offer any advice? Thank you
EDIT: I'm providing some parts of my form code I have. RTSPConnection works just fine, the offending class is RTPStream
public ref class Form1 : public System::Windows::Forms::Form
{
public:
// ... Lots of generated code here ...
//Calls I've written
private: static RTSPConnection * rtsp_connection_ = NULL; //This class works
private: static RTPStream * rtp_connection_ = NULL; //This class does not
bool streaming_;
System::Threading::Thread^ streaming_thread_;
private: System::Void Form1_Load(System::Object^ sender, System::EventArgs^ e) {
if(rtsp_connection_ == NULL)
{
rtsp_connection_ = new RTSPConnection("rtsp://192.168.40.131:8554/smpte");
streaming_ = false;
}
//if(rtp_connection_ == NULL)
// rtp_connection_ = new RTPStream("test");
}
private: System::Void Form1_FormClosing(System::Object^ sender, System::Windows::Forms::FormClosingEventArgs^ e) {
if(rtsp_connection_ != NULL)
rtsp_connection_->StopStreaming();
}
private: System::Void button1_MouseClick(System::Object^ sender, System::Windows::Forms::MouseEventArgs^ e) {
if(!streaming_)
{
//Start Streaming
streaming_thread_ = gcnew Thread(gcnew ThreadStart(&Form1::WorkerThreadFunc));
streaming_thread_->Start();
this->button1->Text = L"Stop Streaming";
streaming_ = true;
}
else
{
//Stop Streaming
if(rtsp_connection_ != NULL)
rtsp_connection_->StopStreaming();
//THIS CALL RIGHT HERE WILL THROW AN ACCESS VIOLATION
if(rtp_connection_ != NULL)
rtp_connection_->StopStreaming();
this->button1->Text = L"Start Streaming";
streaming_ = false;
}
}
};

Answer 1

These two statements appear to contradict each other:
The program hasn't even started running yet, and the new,
problem-causing C++ class hasn't even been constructed yet.
If I comment out the new call, and only have a pointer to this new C++
class, everything compiles just fine.
Q: Could you please post the code where you're calling "new"? Or are you calling "new" - perhaps you just meant "if I comment out my new class"?
Q: Could you please set a breakpoint in your constructor, look at the stack trace, and see who's invoking it? And when?
========== ADDENDUM ==========
I strongly disagree with this statement:
It all hinges on this line: std::ifstream input_file(filename);
where filename is a std::string.
I strong AGREE with this statement:
You get almost the same error in C# if you have static class members
that depend on each other and they aren't initialised in the order you
expect. In C++, if you had a static singleton and another static
member that referred to it
Calling "ifstream" isn't the problem per se. Rather, somehow invoking the class that invokes ifstream before the program has initialized is the problem.
Q: Are you calling "new" on this class? If so, where. Please cut/paste that code.
Per MSDN, you should be able to set "mixed mode debugging". I have lots of different copies of MSVS :) ... but MSVS 2010/C++ doesn't happen to be one of them. Please look at this documentation:
http://msdn.microsoft.com/en-us/library/fz5w87ad.aspx
http://msdn.microsoft.com/en-us/library/cktt23yw