MSDN Documentation

Handling Crashes

Dealing with application crashes is a critical part of software development. This guide outlines common causes of crashes and strategies for effective handling and debugging.

Common Causes of Crashes

• Unhandled Exceptions: Errors in your code that are not caught by exception handling mechanisms.
• Memory Corruption: Issues like buffer overflows, use-after-free, or double-free errors that corrupt the program's memory space.
• Stack Overflow: Occurs when a program's call stack exceeds its allocated memory, often due to infinite recursion.
• External Dependencies: Problems with third-party libraries, drivers, or system services that your application relies on.
• Resource Exhaustion: Running out of system resources such as CPU, memory, or file handles.

Strategies for Crash Handling

1. Graceful Shutdown and Error Reporting

Implement mechanisms to catch critical errors and shut down your application gracefully. This often involves using global exception handlers or signal handlers. When a crash is imminent, attempt to:

• Save any unsaved user data.
• Log detailed error information (call stack, last known state).
• Inform the user that an error occurred and that the application needs to close.
• Optionally, collect diagnostic data or send a crash report to a central server.

void Application_Error(object sender, EventArgs e)
{
    // Get the exception object.
    Exception exc = Server.GetLastError();

    // Log the exception.
    // Consider using a robust logging framework.
    Console.Error.WriteLine("Unhandled exception occurred:");
    Console.Error.WriteLine($"Message: {exc.Message}");
    Console.Error.WriteLine($"Stack Trace: {exc.StackTrace}");

    // Clear the error to prevent a default ASP.NET error page.
    Server.ClearError();

    // Redirect to a user-friendly error page.
    Response.Redirect("error.aspx?handler=Application_Error");
}
                

2. Memory Management and Debugging

Many crashes are memory-related. Tools like Valgrind (for C/C++), AddressSanitizer, or memory profilers in IDEs can help detect these issues:

• Static Analysis: Tools that analyze code without executing it to find potential bugs.
• Dynamic Analysis: Tools that monitor your program during execution to find runtime errors.
• Memory Leak Detection: Identify objects that are no longer needed but are still held in memory.
• Bounds Checking: Ensure array accesses and buffer operations stay within their allocated boundaries.

3. Logging and Diagnostics

Comprehensive logging is invaluable for diagnosing crashes that occur in the wild. Implement logging for:

• Critical events and state changes.
• User actions that precede the crash.
• Errors encountered during operation.
• System information (OS version, hardware).

Consider using structured logging to make it easier to query and analyze logs.

4. Reproducing Crashes

The most effective way to fix a crash is to reliably reproduce it. Work with users or QA teams to gather steps that lead to the crash. If possible, try to:

• Simplify the test case to isolate the problematic code path.
• Use debugging tools to step through the execution flow leading up to the crash.
• Examine the system's state (memory, threads, handles) at the time of failure.

Tools and Techniques

• Debuggers: Essential for stepping through code, inspecting variables, and analyzing call stacks.
• Profilers: Help identify performance bottlenecks and memory issues.
• Crash Dump Analyzers: Tools like WinDbg or LLDB can analyze crash dumps generated by the operating system to understand the state of the application at the time of the crash.
• Unit and Integration Tests: Well-written tests can catch many bugs early in the development cycle, preventing crashes.