From 5debb46f0cac3d60043c7186b3028aa55e1c7492 Mon Sep 17 00:00:00 2001
From: Kouji Matsui <k@kekyo.net>
Date: Thu, 19 Jan 2023 11:28:51 +0900
Subject: [PATCH] Fixed explicitly applied maxstack being ignored.

---
 Mono.Cecil.Cil/CodeReader.cs             |  2 +-
 Mono.Cecil.Cil/CodeWriter.cs             |  3 ++-
 Mono.Cecil.Cil/MethodBody.cs             |  6 +++++-
 Test/Mono.Cecil.Tests/MethodBodyTests.cs | 27 ++++++++++++++++++++++++
 4 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/Mono.Cecil.Cil/CodeReader.cs b/Mono.Cecil.Cil/CodeReader.cs
index 89515d688..1e241857d 100644
--- a/Mono.Cecil.Cil/CodeReader.cs
+++ b/Mono.Cecil.Cil/CodeReader.cs
@@ -92,7 +92,7 @@ void ReadMethodBody ()
 			switch (flags & 0x3) {
 			case 0x2: // tiny
 				body.code_size = flags >> 2;
-				body.MaxStackSize = 8;
+				body.max_stack_size = 8;
 				ReadCode ();
 				break;
 			case 0x3: // fat
diff --git a/Mono.Cecil.Cil/CodeWriter.cs b/Mono.Cecil.Cil/CodeWriter.cs
index 0ec4cc6e2..e2d928664 100644
--- a/Mono.Cecil.Cil/CodeWriter.cs
+++ b/Mono.Cecil.Cil/CodeWriter.cs
@@ -341,7 +341,8 @@ void ComputeHeader ()
 			}
 
 			body.code_size = offset;
-			body.max_stack_size = max_stack;
+			body.max_stack_size = body.is_max_stack_size_set_explicitly
+				? body.max_stack_size : max_stack;
 		}
 
 		void ComputeExceptionHandlerStackSize (ref Dictionary<Instruction, int> stack_sizes)
diff --git a/Mono.Cecil.Cil/MethodBody.cs b/Mono.Cecil.Cil/MethodBody.cs
index 89bfc905c..018f42484 100644
--- a/Mono.Cecil.Cil/MethodBody.cs
+++ b/Mono.Cecil.Cil/MethodBody.cs
@@ -21,6 +21,7 @@ public sealed class MethodBody {
 
 		internal ParameterDefinition this_parameter;
 		internal int max_stack_size;
+		internal bool is_max_stack_size_set_explicitly;
 		internal int code_size;
 		internal bool init_locals;
 		internal MetadataToken local_var_token;
@@ -35,7 +36,10 @@ public MethodDefinition Method {
 
 		public int MaxStackSize {
 			get { return max_stack_size; }
-			set { max_stack_size = value; }
+			set {
+				max_stack_size = value;
+				is_max_stack_size_set_explicitly = true;
+			}
 		}
 
 		public int CodeSize {
diff --git a/Test/Mono.Cecil.Tests/MethodBodyTests.cs b/Test/Mono.Cecil.Tests/MethodBodyTests.cs
index 5af097bc9..becb1db8c 100644
--- a/Test/Mono.Cecil.Tests/MethodBodyTests.cs
+++ b/Test/Mono.Cecil.Tests/MethodBodyTests.cs
@@ -1,4 +1,5 @@
 using System;
+using System.IO;
 using System.Linq;
 
 using Mono.Cecil;
@@ -449,5 +450,31 @@ public void RemoveInstruction ()
 			Assert.AreEqual (first, third.Previous);
 			Assert.IsNull (third.Next);
 		}
+
+		[Test]
+		public void ApplyExplicitMaxStack ()
+		{
+			var path = Path.GetTempFileName ();
+			var module = ModuleDefinition.CreateModule ("FooFoo", ModuleKind.Dll);
+
+			var method = new MethodDefinition ("foo", MethodAttributes.Static, module.TypeSystem.Void);
+			var body = method.Body;
+
+			body.MaxStackSize = 100;
+
+			var il = body.GetILProcessor ();
+
+			var ret = il.Create (OpCodes.Ret);
+			body.Instructions.Add (ret);
+
+			var type = new TypeDefinition ("foo", "foo", TypeAttributes.Public | TypeAttributes.Class, module.TypeSystem.Object);
+			type.Methods.Add (method);
+			module.Types.Add (type);
+
+			module.Write (path);
+
+			using (var read_module = ModuleDefinition.ReadModule (path))
+				Assert.AreEqual (100, read_module.Types [1].Methods[0].Body.MaxStackSize);
+		}
 	}
 }