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Advanced dnSpy tips and tricks

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Digi edited this page Jun 20, 2022 · 9 revisions

These are if you're already a bit comfortable with what dnSpy is and how to use its decompiled code navigation and basic debugging.

Breakpoints

These pause the code execution at a specific line just like exceptions, but you don't need an error or to edit the code to do it, just right-click on any code line to add a breakpoint.

When dnSpy is attached and the game goes over your breakpoints it will pause the execution just like an exception (relevant: Navigating paused code).

Breakpoints for PB/mod scripts.

Mods and PB scripts are compiled in memory and can be found in Debug -> Windows -> Modules (Ctrl+Alt+U, requires dnSpy to be attached) at the end, PB scripts have <EntityId>-<CustomName>.dll name format.

When you recompile a PB or reload a world the scripts are compiled into new modules, that means you need to open the new one.

Or you can avoid that module fiddling and just throw exceptions inside a try-catch in your own code to act like a breakpoint (relevant: Catching errors (exceptions)).

Seeing local variables when code is paused

Local variables are optimized out so in order to see their values when execution is paused you need to have the libraries start as unoptimized.

dnSpy locals window - variables can't be evaluated

Note: Simply attaching dnSpy to the game will cause any future in-game compilations to be built unoptimized for the duration of the game session. (mods recompile on world load, PBs can be recompiled in terminal), that means you don't need to launch the game through dnSpy to debug PB/mod code effectively.

But for game's code you need to start the game with dnSpy in order to load its libraries as unoptimized, see below on how to properly do that.

Note: Starting the game with dnSpy will run noticeably slower.

Starting the game with dnSpy:

  1. Download: steam_appid.txt as a file

  2. Place steam_appid.txt in the game's Bin64 (e.g. <Steam>/SteamApps/common/SpaceEngineers/Bin64)

  3. Start dnSpy (but not the game).

  4. dnSpy: Debug -> Start Debugging (F5)

  5. In the Executable field press [...] and go to game's Bin64 again and pick SpaceEngineers.exe

    Optional: add -skipintro -nosplash in the Arguments field.

    dnSpy start window example

  6. Do your exception catching or breakpoint stuff.

  7. Local variables now have values!

A big thank you goes to Digi for writing this tutorial.

Do you have questions, comments, suggestions for improvements? Is there something I can do better? Did I make a mistake? Please add an issue here, and prefix your issue title with Wiki. Thank you, your help will be very appreciated!

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