Unity3D 降低IL2CPP编译可执行文件大小

项目开始使用IL2CPP编译，后果是可执行文件急剧增加。

google后发现国外一大神写的方法，原帖在这http://forum.unity3d.com/threads/suggestion-for-reducing-the-size-of-il2cpp-generated-executable.338986/

懒得愿意看原帖的直接看我的方法吧

1、新建一个Mono工程，命名成UnusedByteCodeStripper2，贴如下面代码，编译出 UnusedByteCodeStripper2.exe

using System;
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Reflection;
using System.Text;
using Mono.Cecil;
using Mono.Collections.Generic;

namespace RemoveAttributesTool
{
internal class Program
{
private static readonly string[] RemoveAttributesNames =
{
// Just information
"System.Runtime.CompilerServices.CompilerGeneratedAttribute",
"System.Runtime.CompilerServices.ExtensionAttribute",
"System.ParamArrayAttribute",
"System.Reflection.DefaultMemberAttribute",
"System.Diagnostics.DebuggerStepThroughAttribute",
"System.Diagnostics.DebuggerHiddenAttribute",
"System.Diagnostics.DebuggerDisplayAttribute",
"System.Diagnostics.CodeAnalysis.SuppressMessageAttribute",
"System.ObsoleteAttribute",
"System.AttributeUsageAttribute",
"System.MonoTODOAttribute",
// Not relative
"System.CLSCompliantAttribute",
"System.Runtime.InteropServices.ComVisibleAttribute",
"System.Runtime.ConstrainedExecution.ReliabilityContractAttribute",
// Editor only
"UnityEngine.AddComponentMenu",
"UnityEditor.MenuItem",
"UnityEngine.ContextMenu",
"UnityEngine.ExecuteInEditMode",
"UnityEngine.HideInInspector",
"UnityEngine.TooltipAttribute",
"UnityEngine.DisallowMultipleComponent",
"UnityEngine.Internal.ExcludeFromDocsAttribute",
};

private static readonly string[] AdditionalDllFileNames =
{
"UnityEngine.dll",
"mscorlib.dll",
"System.dll",
"System.Core.dll",
"System.Xml.dll",
"Mono.Security.dll",
};

private static void Main(string[] args)
{
// Process

for (var i = 0; i < args.Length; i++)
{
switch (args[i])
{
case "-a":
ProcessDll(args[i + 1]);
break;
}
}

foreach (var fileName in AdditionalDllFileNames)
{
if (File.Exists(fileName))
ProcessDll(fileName);
}

// Run original executables

var monoCfgDir = Environment.GetEnvironmentVariable("MONO_CFG_DIR");
var monoPath = monoCfgDir.Substring(0, monoCfgDir.Length - 3) + "bin/mono";

var currentModulePath = Assembly.GetExecutingAssembly().Location;
var orgModulePath = currentModulePath.Substring(0, currentModulePath.Length - 3) + "org.exe";

var orgArgs = '"' + orgModulePath + '"' + ' ' + string.Join(" ", args.Select(a => '"' + a + '"'));
var handle = Process.Start(monoPath, orgArgs);
handle.WaitForExit();
}

private static void ProcessDll(string dllPath)
{
AssemblyDefinition assemblyDef;

using (var assemblyStream = new MemoryStream(File.ReadAllBytes(dllPath)))
{
assemblyDef = AssemblyDefinition.ReadAssembly(assemblyStream);
}

ProcessAssembly(new[] {assemblyDef});

using (var assemblyStream = File.Create(dllPath))
{
assemblyDef.Write(assemblyStream);
}
}

private static void ProcessAssembly(AssemblyDefinition[] assemblyDefs)
{
foreach (var assemblyDef in assemblyDefs)
{
foreach (var moduleDef in assemblyDef.Modules)
{
foreach (var type in moduleDef.Types)
RemoveAttributes(type);
}
}
}

private static void RemoveAttributes(TypeDefinition typeDef)
{
RemoveAttributes(typeDef.FullName, typeDef.CustomAttributes);

foreach (var field in typeDef.Fields)
RemoveAttributes(field.Name, field.CustomAttributes);

foreach (var property in typeDef.Properties)
RemoveAttributes(property.Name, property.CustomAttributes);

foreach (var method in typeDef.Methods)
RemoveAttributes(method.Name, method.CustomAttributes);

foreach (var type in typeDef.NestedTypes)
RemoveAttributes(type);
}

private static void RemoveAttributes(string ownerName, Collection<CustomAttribute> customAttributes)
{
foreach (var attrName in RemoveAttributesNames)
{
var index = -1;
for (var i = 0; i < customAttributes.Count; i++)
{
var attr = customAttributes[i];
if (attr.Constructor != null && attr.Constructor.DeclaringType.FullName == attrName)
{
index = i;
break;
}
}

if (index != -1)
customAttributes.RemoveAt(index);
}
}
}
}

　　

2、进入Unity目录

Unity/Contents/Frameworks/Tools/UnusedByteCodeStripper2

3、把原来的UnusedByteCodeStripper2.exe命名成 UnusedByteCodeStripper2.org.exe

4、把刚生成 UnusedByteCodeStripper2.org.exe 贴进入。

5、用Unity生成xcode，测试结果