Issues creating a call to Nullable<Boolean>.Value

[Austin Brkich]

I am having issues trying to create a instruction to call Nullable<Boolean>.Value

The closest I have come is by using the following code as it will generate ILCode that appears to be almost identical to what it was originally. I have also included the Test.exe that I am modifying, In this example I am replacing a call to Nullable<Boolean>.Value that was generated from the compiler with one generated by Mono.Cecil, but I am getting the following error when trying to run the modified executable.

https://gist.github.com/7H3LaughingMan/311662c07b8bf8f8d2c6
https://dl.dropboxusercontent.com/u/7231478/Test.exe

Unhandled Exception: System.TypeLoadException: Could not load type 'System.Nullable`1' from assembly 'Test, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' due to value type mismatch.

   at Test.Program.Main(String[] args)

[Jb Evain]

Hi Austin,

Yeah dealing with generics is not always a pleasant experience right now.

Here's code that works:

http://paste2.org/YeD09NEI

Always work with definitions until you need to create references in
your module, it's much easier. In this case, retrieve the definition
from get_Value, up until the point where you create a reference.

And then there's the MakeGeneric method that should be in
Mono.Cecil.Rocks but isn't.

Jb

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[Austin Brkich]

Somewhat related to this issue is that I am having issued making a call now to Nullable<Boolean>.HasValue but I am only able to replicate this in my actual program. The program is an attempt to add a Modding API to a game and it does this by parsing an XML file to figure out what needs to be inserted and where.

This file represents how Call OpCodes are handled.
https://github.com/7H3LaughingMan/PhiScript/blob/master/PhiPatcher/Instructions/Call.cs

This is the actual XML file with all the modifications. I will include the part that I am having issues with.

https://github.com/7H3LaughingMan/PhiScript/blob/master/PhiPatcher/Modifications.xml

<Instruction OpCode="Call" Assembly="CoreLibrary" Type="System.Nullable`1" Method="get_HasValue">

<GenericParameter Assembly="CoreLibrary" Type="System.Boolean" />

</Instruction>

This is the exception I am getting.
InvalidProgramException: Invalid IL code in Planetbase.ConstructionComponent:canProduce (): IL_000a: call      0x0a0001bc

And using ILSpy this is the resulting IL code.
IL_000a: call instance bool valuetype [mscorlib]System.Nullable`1<bool>::get_HasValue()

[Jb Evain]

Hi,

I'm not going to be able to debug your entire program I'm afraid.

What happens if you run peverify on your modified binary?

Thanks,
Jb

[Austin Brkich]

This is what I get when running peverify

[IL]: Error: [C:\Program Files (x86)\Steam\SteamApps\common\Planetbase\Planetbase_Data\Managed\Assembly-CSharp.dll : Planetbase.ConstructionComponent::canProduce][offset 0x0000000A][found value 'System.Nullable`1[System.Boolean]'][expected address of value 'System.Nullable`1[System.Boolean]'] Unexpected type on the stack.

[IL]: Error: [C:\Program Files (x86)\Steam\SteamApps\common\Planetbase\Planetbase_Data\Managed\Assembly-CSharp.dll : Planetbase.ConstructionComponent::canProduce][offset 0x00000013][found value 'System.Nullable`1[System.Boolean]'][expected address of value 'System.Nullable`1[System.Boolean]'] Unexpected type on the stack.

2 Error(s) Verifying Assembly-CSharp.dll

[Jb Evain]

Hi Austin,

Peverify is telling you that the semantic of the code is wrong.

Can you pastebin the entire IL of the method?

Jb

[Austin Brkich]

IL_0000: ldarg.0
IL_0001: call valuetype [mscorlib]System.Nullable`1<bool> [PhiScript]PhiScript.Manager.ConstructionComponentManager::OnCanProduce(class ['Assembly-CSharp']Planetbase.ConstructionComponent)
IL_0006: stloc.s 8
IL_0008: ldloc.s 8

IL_000a: call instance bool valuetype [mscorlib]System.Nullable`1<bool>::get_HasValue()

IL_000f: brfalse.s IL_0019

IL_0011: ldloc.s 8
IL_0013: call instance !0 valuetype [mscorlib]System.Nullable`1<bool>::get_Value()
IL_0018: ret

This is my section of code that I am inserting. The rest of the Method is code that doesn't really matter, but if you need that let me know.

[Jb Evain]

You need to:

ldloca
call get_HasValue

Nullable are value types.

Jb

[Austin Brkich]

Thanks for the help, that fixed the issue. Didn't realize there was a
difference between ldloc and ldloca.

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