What’s a Release Build compared to a Debug build

Release builds of a .NET application (by default) add optimizations, remove any debug code from the build, i.e. anything inside #if DEBUG is remove as well as Trace. and Debug. calls being removed. You also have reduced debug information. However you will still have .PDB files…

PDB files are generated by the compiler if a project’s properties allow for .PDB file to be generated. Simply check the project properties, select the Build tab and the Advanced… button. You’ll see Debug Info, which can be set to full, pdb-only or none. Obviously none will not produce any .PDB files.

At this point, I do not know the differences between pdb-only and full, if I find out I’ll amend this post, but out of the box, Release builds used pdb-only whilst Debug use full.

So what are .PDB files ?

Simply put – PDB files contain symbol information which allows us to map debug information to source files when we attach a debugger and step through the code.

Debugging a Release Build

It’s often the case that we’ll create a deployment of a Release build without the PDB files, this may be due to a desire to reduce the deployment foot print or some other reason. If you cannot or do not wish to deploy the PDB’s with an application then we should store them for a specific version of a release.

Before attaching our debugger (Visual Studio) we ned to add the PDB file locations to Visual Studio. So select the Debug menu, then Options and Settings. From here select Debugging | Symbols from the tree view on the left of the Options dialog. Click on the add folder button and type in (or paste) the folder name for the symbols for the specific Release build.

Now attach Visual Studio using Debug | Attach Process and the symbols will get loaded for the build and you can now step through the source code.

Let’s look at a real example

An application I work on deploys over the network and we do not include PDB files with it so we can reduce the size of the deployment. If we find a bug only repeatable “production” we cannot step through the source code related to the build without both a version of the code related to the release and without the PDB files for that release.

What we do is, when our continuous integration server runs, it builds a specific version of the application as a release build. We embed the source repository revision into the EXE version number. This allows us to easily check out the source related to that build if need be.

During the build process, we the copy the release build to a deployment folder, again using the source code revision in the folder name. We (as already mentioned) remove the PDB files (and Tests and other such files are also obviously removed). However we don’t just throw away the PDB’s, we instead copy them to a folder similarly named to the release build but with the name Symbols within the folder name (and ofcourse with the same version number). The PDB’s are all copied to this folder and now accessible if we need to debug a release build.

Now if the Release (or a production) build is executed and an error occurs or we just need to step through code for some other reason, we can get the specific source for the deployed version, direct Visual Studio to the PDB files for that build and now step through our code.

So don’t just delete your PDB’s store them in case you need to use them in the future.

Okay, how do we use the symbol/PDB files

So, in Visual Studio (if you’re using that to debug/step through your code). Obviously open your project with the correct source for your release build.

In the Tools | Options dialog, select the Debugging parent node in the dialog and then select Symbols or ofcourse just type Symbols into the search text box in Visual Studio 2013.

Now press the folder button and type in the location of your PDB files folder. Note that this option doesn’t have a folder browse option so you’ll need to type (or copy and paste) the folder name yourself.

Ensure the folder is checked so that Visual Studio will load the symbols.

Now attach the debugger to your release build and Visual Studio will (as mentioned) locate the correct symbols and attach them and then allow you to step through your source.

See Specify Symbol (.pdb) and Source Files in the Visual Studio Debugger for more information and some screen shots of the process just described.