Methodology and Census Internals

Methodology and Census Internals

This document details the internal logic of tools/measure-bodies.py and tools/measure-owned.py, the four classifier bugs discovered during testing, and the complete benchmark data for Unity IL2CPP vs Mono builds.

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Benchmark Findings

To verify whether a 0.00% survival rate is an IL2CPP characteristic or a decompiler defect, the census scripts were run across four commercial Unity titles spanning both scripting backends and Unity versions from 2017 to Unity 6 (2026).

Whole-Project Benchmark Results

Game	Unity Version	Scripting Backend	Extractor Tool	Files	Total Methods	Empty	Stubs	Live Bodies	Live %
House Flipper	2019.4	Mono	ilspycmd	4,528	231,243	5,120	6,448	219,675	95.00%
Car Mechanic Simulator 2018	2017.4	Mono	ilspycmd	114	1,040	18	55	967	92.98%
MiSide	2021.3	IL2CPP	AssetRipper	1,225	4,899	3,408	1,491	0	0.00%
Data Center	6000.4 (Unity 6)	IL2CPP	Cpp2IL	282	2,549	0	2,549	0	0.00%

Game-Owned Code vs Vendor Middleware Split

Whole-project numbers flatten studio code and third-party libraries together. In Mono games, middleware libraries (written for distribution) survive at higher rates than game code, inflating the overall score. In IL2CPP games, IL2CPP compiles everything to native code regardless of whether a library is open-source.

measure-owned.py separates studio code from vendor middleware (Steamworks, Rewired, Sirenix, Odin, I2.Loc, etc.):

Game	Backend	Category	Files	Methods	Live Bodies	Live %
House Flipper	Mono	Studio Owned	4,210	218,860	208,216	95.14%
	Mono	Vendor Middleware	318	12,383	11,459	92.54%
Car Mechanic Simulator 2018	Mono	Studio Owned	22	130	108	83.08%
	Mono	Vendor Middleware	92	910	859	94.40%
MiSide	IL2CPP	Studio Owned	781	3,309	0	0.00%
	IL2CPP	Vendor Middleware	444	1,590	0	0.00%
Data Center	IL2CPP	Studio Owned	258	2,366	0	0.00%
	IL2CPP	Vendor Middleware	24	183	0	0.00%

Note: On Car Mechanic Simulator 2018 (Mono), studio code is 83.08% live while bundled middleware is 94.40%. Third-party libraries inflate whole-project averages.

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How the Census Classifier Works (measure-bodies.py)

tools/measure-bodies.py uses regex parsing to classify every recovered method into one of three categories:

1. Empty: 0 statements between braces {}.
2. Trivial Stub: Contains only dummy default return values, throw null;, or out parameter default assignments.
3. Real Body: Contains actionable programming logic.

1. Signature Recognition Regex

sig = re.compile(
    r'^[ \t]*(?:\[[^\]]*\][ \t]*)*'
    r'(?:public|private|protected|internal)[ \t]+'
    r'(?:(?:static|virtual|override|sealed|abstract|extern|async|new|unsafe)[ \t]+)*'
    r'(?![ \t]*(?:class|struct|enum|interface|delegate)\b)'
    r'[\w<>\[\],\.\?]+[ \t]+\w+[ \t]*\([^;{]*\)[ \t]*$'
)

2. Stub Statement Classifier

TRIVIAL_ZERO = (r"(?:0[uUlLfFdDmM]{0,2}|0\.0[fFdDmM]?|'\\0'"
                r'|""|string\.Empty|null|default|false|true)')

TRIVIAL_VALUE = (r'(?:default\([^()]*\)'
                 r'|\((?:[\w\.]+)\)\s*' + TRIVIAL_ZERO +
                 r'|' + TRIVIAL_ZERO +
                 r'|new [\w<>\[\],\. ]+\(\))')

TRIVIAL_STMT = re.compile(
    r'(?:return(?:\s+' + TRIVIAL_VALUE + r')?'
    r'|throw null'
    r'|throw new (?:System\.)?NotImplementedException\(\)'
    r'|[\w\.\[\]]+\s*=\s*' + TRIVIAL_VALUE + r')\s*;'
)

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History of Four Classifier Corrections

Before reaching the validated 0.00% figure, the headline number was published wrong three times. Every error was caught by opening the decompiled files and reading them by hand rather than trusting script output:

1. 8.22% — Working Copy Leak

• Cause: Measured a working project directory that already contained hand-written replacement code.
• Correction: Always measure pristine, untouched decompiler exports directly out of AssetRipper or Cpp2IL.

2. 7.70% — Multi-Statement out Parameter Stubs

• Cause: The original classifier only recognized single-statement method bodies. When IL2CPP strips a method with out parameters, C# decompilers emit stub assignments for every parameter before returning:

  public static bool GetAutoResolution(out int width, out int height)
  {
      width = default(int);
      height = default(int);
      return false;
  }

  Because this body contains three statements, single-statement matching misclassified it as real code.
• Correction: Updated is_trivial(txt) to verify if all statements in the body match stub assignment/return patterns.

3. 3.04% — Missing Literal Stub Patterns

• Cause: The original stub regex matched 0 and null, but missed type-casted zero values such as (IntPtr)0, 0uL, 0.0, or '\0'. This credited 149 Steamworks P/Invoke stub functions as live code.
• Correction: Expanded TRIVIAL_ZERO to cover explicitly typed zero literals, unsigned longs, floats, null pointers, and empty strings.

4. Vendor Namespace Prefix Matching Bug

• Cause: measure-owned.py originally checked string prefixes using segment.startswith(vendor). The entry gog (for GOG Galaxy) matched GogoGaga.OptimizedRopesAndCables, and properties matched every assembly's Properties/AssemblyInfo.cs.
• Correction: Namespace matching was rewritten to enforce dot-separated namespace boundaries (comps[:len(vc)] == vc). unity now matches Unity.Entities but never a game namespace starting with those letters (like UnityChanFanGame).