C++ Exception-Handling Tricks for Linux
By Sachin O. Agrawal2005-04-12
Managing Exceptions in Constructors and Destructors
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Managing exceptions in constructors and destructors
Per ANSI C++, during construction and destruction of global (static global) variables, catching exceptions is not possible. Hence, ANSI C++ does not recommend throwing exceptions in the constructor and destructor of a class whose instances may be defined globally (static-globally). The other way to say it is, never define a global (static global) instance of a class whose constructor or destructor may throw exceptions. However, if you assume a specific compiler and a specific system, it may be doable, and fortunately, with GCC on Linux, it is.
This is demonstrated using the ExceptionHandler class, which again adopts a singleton design pattern. Its constructor registers an un-caught handler. Since there can be only one un-caught handler per process active at a time, the constructor should be invoked only once; hence, the reason for the singleton pattern. A global (static global) instance of ExceptionHandler should be defined prior to the definition of the actual global (static global) variable in question.
Listing 3. Handling exceptions in a constructor
class ExceptionHandler
{
private:
class SingleTonHandler
{
public:
SingleTonHandler()
{
set_terminate(Handler);
}
static void Handler()
{
// Exception from construction/destruction of global variables
try
{
// re-throw
throw;
}
catch (SegmentationFault &)
{
cout << "SegmentationFault" << endl;
}
catch (FloatingPointException &)
{
cout << "FloatingPointException" << endl;
}
catch (...)
{
cout << "Unknown Exception" << endl;
}
//if this is a thread performing some core activity
abort();
// else if this is a thread used to service requests
// pthread_exit();
}
};
public:
ExceptionHandler()
{
static SingleTonHandler s_objHandler;
}
};
//////////////////////////////////////////////////////////////////////////
class A
{
public:
A()
{
//int i = 0, j = 1/i;
*(int *)0 = 0;
}
};
// Before defining any global variable, we define a dummy instance
// of ExceptionHandler object to make sure that
// ExceptionHandler::SingleTonHandler::SingleTonHandler() is invoked
ExceptionHandler g_objExceptionHandler;
A g_a;
//////////////////////////////////////////////////////////////////////////
int main(int argc, char* argv[])
{
return 0;
}
Tutorial Pages:
» Four Techniques for Dealing with Built-in Language Limitations
» Retaining exception source information
» Managing Signals
» Managing Exceptions in Constructors and Destructors
» Handling Exceptions in Multi-Threaded Programs
» Conclusion
» Resources
First published by IBM DeveloperWorks
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