Rider ↔ Unity IL2CPP Debugger: Why do breakpoints sometimes fail to resolve?

Why IL2CPP breakpoints sometimes fail to resolve

When Rider’s Enable IL2CPP debugging setting is turned on, breakpoints in managed C# scripts may still be missed. The issue usually stems from how Unity emits and places the generated .pdb symbol files, and from Riders symbol‑loading logic.

Likely explanation

• Rider expects the .pdb files to be alongside the players assembly or in a known intermediate folder. Unity moves this folder between 2020, 2021 and 2022 releases, so a path that worked in one version may be wrong in another.
• Even with the setting enabled, Rider does not auto‑discover the PDB for player builds unless the build is a Development Build and Script Debugging is turned on in Unity Player Settings.
• IL2CPP AOT optimisations, code stripping or inlining can remove the method body, causing breakpoints to appear hollow or be skipped entirely.

Confirmed facts

• The Enable IL2CPP debugging checkbox is required but not sufficient.
• Unity must have Script Backend = IL2CPP, Script Debugging = true, and the project must be built as a Development Build for player targets; otherwise Unity does not emit the managed PDBs Rider needs.
• PDB location is version‑sensitive and platform‑specific. Assuming a fixed path across Unity 2022.x releases or between Editor and Windows/Android/iOS builds will cause missed symbols.
• Stale or mismatched PDBs (different timestamps or names than the loaded assemblies) prevent breakpoint resolution.

Steps to try (in order)

1. In Unity Player Settings set Script Backend to IL2CPP, enable Script Debugging, and check Development Build for the target platform.
2. Perform a clean rebuild (delete Library and obj folders or use Build > Clean) so that PDB timestamps match the freshly built assemblies.
3. Start a Rider debug session and open the Debugger Show Log window. Look for Symbol load messages that list the PDB path and name.
4. If the PDB is not listed or points to a wrong folder, manually add the build output folder containing the .pdb files as a symbol path in Riders Edit Preferences Build Execution Deployment Debugger Symbols.
5. Test a breakpoint in a simple method that is not inlined or stripped (e.g., a method with no MethodImplOptions.NoInlining attribute).

If you are debugging a standalone player, please confirm whether the build is a Development Build; the recommended steps differ for Release builds because Unity does not emit debug symbols.