Using a good debugger can save you a lot of development time.
The debugger you use must match the C compiler Wireshark was compiled with, otherwise the debugger will simply fail or you will only see a lot of garbage.
You can use the integrated debugger of Visual Studio if your toolchain includes it. Open the solution in your build directory and build and debug as normal with a Visual Studio solution.
To set the correct paths for Visual Studio when running Wireshark under the debugger, add the build output directory to the path before opening Visual Studio from the same command prompt, e.g.
C:\Development\wsbuild64>set PATH="%PATH%;C:\Development\wsbuild64\run\RelwithDebInfo" C:\Development\wsbuild64>wireshark.sln
for PowerShell use
PS C:\Development\wsbuild64>$env:PATH += ";$(Convert-Path run\RelWithDebInfo)" PS C:\Development\wsbuild64>wireshark.sln
When Visual Studio has finished loading the solution, set the executable to be run in the debugger, e.g. Executables\Wireshark, by right clicking it in the Solution Explorer window and selecting "Set as StartUp Project". Also set the Solution Configuration (usually RelWithDebInfo) from the droplist on the toolbar.
Currently Visual Studio regards a command line build as incomplete, so will report that some items need to be built when starting the debugger. These can either be rebuilt or ignored as you wish.
The normal build is an optimised release version so debugging can be a bit difficult as variables are optimised out into registers and the execution order of statements can jump around.
If you require a non-optimised version, then build using a debug configuration.
You can also use the Microsoft Debugging Tools for Windows toolkit, which is a standalone GUI debugger. Although it’s not that comfortable compared to debugging with the Visual Studio integrated debugger it can be helpful if you have to debug on a machine where an integrated debugger is not available.
You can get it free of charge from Microsoft in several ways, see the Debugging tools for Windows page.
You can also use Chocolatey to install WinDbg:
PS:\> choco install windbg
To debug Wireshark using WinDbg, open the built copy of Wireshark using the File → Open Executable… menu, i.e. C:\Development\wsbuild64\run\RelWithDebInfo\Wireshark.exe. To set a breakpoint open the required source file using the File → Open Source File… menu and then click on the required line and press F9. To run the program, press F5.
If you require a non-optimised version, then build using a debug configuration, e.g.
msbuild /m /p:Configuration=Debug Wireshark.sln. The build products will be found