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Showing posts from July, 2009

Finding CLR exceptions without visual studio

(If you want to understand what exception code 0xe0434352 is, read this post ) Often exceptions are thrown and caught and you don't see them. You probably know how to debug this in Visual Studio, so let me show you how to do it in cdb. Sample Code: class Program { static void Main(string[] args) { foreach (var x in Enumerable.Range(0,2000)) { Thread.Sleep(TimeSpan.FromSeconds(1)); Console.WriteLine("Hello World"); ThrowAndCatchException(); } } private static void ThrowAndCatchException() { try { throw new NotImplementedException(); } catch(Exception) { } } } Output of the application: Hello World Hello World Hello World Nothing about an exception, but you're sure it's happening behind the covers -- fire up cdb: C:\Program Files\Debugging Tools for Windows (x64)>cdb -pn consoleapplication3.exe <SNIP> ModLoad: 000007fe`f7e90000 000007fe`f7eb4000 C:\Windows\Mi

Why write programs that don't modify variables?

Slews of bugs happen because variable have values you aren't expecting. To minimize this class of bugs I use a technique a lot of people find surprising. I try to only assign and never modify variables. In C++, I make almost all my variables const. C++ people are now saying -- Um if all your values are const how do you write a for loop? In C++ I can't help myself, I'm stuck with a variable modification eg: for (size_t x=0;x<6;x++) printf("%d",x) In python the for loop naturally iterates over a sequence so you don't need to modify a value: for x in range(6): print x In C#, you can use either the C++ syntax or a more python syntax via foreach: for (int x=0;x<6;x++) Console.WriteLine(x); or foreach (var x in Enumerable.Range(0,6)) Console.WriteLine(x) I use the foreach syntax which people initially find confusing. But its value starts to shine when using non zero starting values. Assume I need to generate 113 numbers starting at 27. Which

How to attach to an already running debugger target using cdb.

For the last year when I wanted to attach to a process using cdb, I'd attach by PID. This meant i'd need to the following dance: C:\Program Files\Debugging Tools for Windows (x64)>tlist |findstr firefox 9128 cmd.exe findstr firefox 276 firefox.exe Restore Session - Vimperator C:\Program Files\Debugging Tools for Windows (x64)>cdb -p 276 It turns out you can just do: C:\Program Files\Debugging Tools for Windows (x64)>cdb -pn firefox.exe Microsoft (R) Windows Debugger Version 6.11.0001.404 AMD64 Copyright (c) Microsoft Corporation. All rights reserved. If there are multiple instances of your process, you'll still need to use tlist to find the PID you're interested in.