Sunday 6 September 2009

Dependency Walker for Windows binaries

I find Dependency Walker a very useful utility. This helps us to scan any of windows binaries (exe, dll ...).

It can dissect almost any type of windows binary file, to show up all possible details hidden within.

Listing few of the details this utility can provide,

  • Basic binary properties Ex: physical path, version info, etc.
  • Exported functions with their signatures and ordinal numbers.
  • Recursive list of dependent libraries and their details.

It didn’t took much time for me to discover the power of this tiny tool which is distributed as apart of MS Visual Studio Tools. This can also be downloaded for free at http://www.dependencywalker.com/.

Below is one of such situation, where this tool helped me to rapidly identify and debug the problem.

I was building Qt for Win with ‘-openssl-linked’ option and this required me to download the openSSL libraries separately. I had downloaded and copied ‘libeay32.dll’ under Qt’s bin folder.

Even though Qt compiled without any problems, I had issues with launching few of the processes which had dependency over libeay32.dll. For some reasons, loader started complaining about missing ordinal in libeay32.dll.

Dependency walker came into rescue. I simply loaded the failing process into DependencyWalker and it listed all dependent DLLs with respective details. I could just walk to the libeay32.dll and examine its version.

There you go! It was loading an older version of DLL which had been installed as part of Wireless monitor app. Since PATH variable had the wireless app’s path occurring before Qt’s bin path, it was always picking the older DLL from wrong location which caused the issue.

It hardly took me few minutes to identify and fix the issue.

Hope this is useful :)