Killing Floor UnrealScript Decompilation

Decompilation is useful for learning from old packages, recovering behavior, and maintaining abandoned mods. It should not be used as an excuse to steal work. Credit authors and respect their work.

Bytecode Versus UnrealScript

UnrealScript compilation turns readable script into engine bytecode. That conversion loses some structure. A decompiler can reconstruct behavior, but it often cannot recover the original style.

Expect output that works but looks worse than the original code.

Loop Cleanup

for loops may decompile into labels and goto statements. The behavior can be correct, but readability suffers.

When you see repeated patterns such as:

J0x07:
if (...)
{
  ...
  goto J0x07;
}

convert them back into normal for or while loops. Also replace explicit break and continue comments with real break and continue statements when the intent is clear.

Replication Blocks

Replication statements can miss semicolons. If you see a replicated variable without ;, add it manually:

replication
{
  reliable if (bNetInitial && Role == ROLE_Authority)
    CsHDRI;
}

Defaultproperties

defaultproperties shown by a decompiler may be incomplete or unreliable, especially when subobjects are involved. A safer workflow is to export classes manually and compare output.

Useful command pattern:

ucc.exe batchexport PACKAGENAME.u class uc ../DIRECTORY/
pause

Else If Cleanup

Decompiled code can turn else if into nested else { if (...) { ... } } blocks. Simplify them back into normal else if chains when behavior matches.

Enumeration Detection

Enum values may appear as raw integers. Replace numeric constants with meaningful enum names by checking class definitions.

Examples:

Raw value	Better expression
Level.NetMode == 3	Level.NetMode == NM_Client
RemoteRole = 2	RemoteRole = ROLE_SimulatedProxy

Cleanup Checklist

1. Export or inspect package classes.
2. Restore readable loops.
3. Add missing replication semicolons.
4. Verify defaultproperties.
5. Convert nested if blocks back to else if where appropriate.
6. Replace enum integers with named constants.
7. Compile and test behavior before publishing changes.

Related Pages

• UnrealScript modding setup
• UnrealScript profiling