Igor's Computer Blog

In this post I'll show you how to use CDB to intercept CreateFile and see what files your application is opening. For this problem, Process Monitor is often a better tool, but the techniques I demonstrate work for any API you should learn them. This won't take much time, so if you've never done this before I recommend you follow along. First Load CDB against cmd: C:\Program Files\Debugging Tools for Windows (x64)>cdb.exe cmd.exe Microsoft (R) Windows Debugger Version 6.12.0000.526 AMD64 Copyright (c) Microsoft Corporation. All rights reserved. CommandLine: cmd.exe Symbol search path is: *** Invalid *** **************************************************************************** * Symbol loading may be unreliable without a symbol search path. * * Use .symfix to have the debugger choose a symbol path. * * After setting your symbol path, use .reload to refresh symbol locations. * ******************...

(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...

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 ...

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.

Maybe I'm weird, but I giggle when people talk about databases crying. The Flickr search api justifies a requirement as follows: Geo queries require some sort of limiting agent in order to prevent the database from crying.