Re: CxxFrameHandler problem

[Steven Edwards]

> That's a start, yes, thanks. I'll need a more
> complete example with
> nested try blocks, destructors all over the place,
> typed exceptions,
> etc. to make sure I understand all the compiler
> internal structures;
> but I can at least try to make that simple case not
> crash...

Taken from MSDN (see fair use) here is the msdn
example page.

------

The following example demonstrates C++ exception
handling using classes with destructor semantics. It
declares two C++ classes; one (class CTest) for
defining the exception object itself, and the second
(class CDtorDemo) for demonstrating the destruction of
a separate frame object during stack unwinding:
Example

// exceptions_Exception_Examples.cpp
// compile with: /EHsc
#include <iostream>

using namespace std;
void MyFunc( void );

class CTest
{
public:
    CTest(){};
    ~CTest(){};
    const char *ShowReason() const { return "Exception
in CTest class."; }

};

class CDtorDemo
{
public:
    CDtorDemo();
    ~CDtorDemo();
};

CDtorDemo::CDtorDemo()
{
    cout << "Constructing CDtorDemo." << endl;
}

CDtorDemo::~CDtorDemo()
{
    cout << "Destructing CDtorDemo." << endl;
}

void MyFunc()
{

CDtorDemo D;
    cout<< "In MyFunc(). Throwing CTest exception." <<
endl;
    throw CTest();
}

int main()
{
    cout << "In main." << endl;
    try
    {
        cout << "In try block, calling MyFunc()." <<
endl;
        MyFunc();
    }
    catch( CTest E )
    {
        cout << "In catch handler." << endl;
        cout << "Caught CTest exception type: ";
        cout << E.ShowReason() << endl;
    }
    catch( char *str )
    {
        cout << "Caught some other exception: " << str
<< endl;
    }
    cout << "Back in main. Execution resumes here." <<
endl;
    return 0;
}

If a matching catch handler is found, and it catches
by value, its formal parameter is initialized by
copying the exception object. If it catches by
reference, the parameter is initialized to refer to
the exception object. After the formal parameter is
initialized, the process of "unwinding the stack"
begins. This involves the destruction of all automatic
objects that were constructed (but not yet destructed)
between the beginning of the try block associated with
the catch handler and the exception's throw site.
Destruction occurs in reverse order of construction.
The catch handler is executed and the program resumes
execution following the last handler (that is, the
first statement or construct that is not a catch
handler).
Output

In main.
In try block, calling MyFunc().
Constructing CDtorDemo.
In MyFunc(). Throwing CTest exception.
Destructing CDtorDemo.
In catch handler.
Caught CTest exception type: Exception in CTest class.
Back in main. Execution resumes here.

Note the declaration of the exception parameter in
both catch handlers:

catch( CTest E )
{ // ... }
catch( char *str )
{ // ... }

You do not need to declare this parameter; in many
cases it may be sufficient to notify the handler that
a particular type of exception has occurred. However,
if you do not declare an exception object in the
exception declaration, you will not have access to the
object in the catch handler clause. For example:

catch( CTest )
{ 
    // No access to a CTest exception object in this
handler.
}

A throw expression with no operand re-throws the
exception currently being handled. Such an expression
should appear only in a catch handler or in a function
called from within a catch handler. The re-thrown
exception object is the original exception object (not
a copy). For example:

try
{
    throw CSomeOtherException();
}
catch(...)      // Handle all exceptions
{
    // Respond (perhaps only partially) to exception
    //...

throw;      // Pass exception to some other
handler
}

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