Bug in Mono.Cecil

By | 2010-03-20

I’m encountering this annoying bug in Mono.Cecil… It seems that when modifying the assembly it calculates wrong offset, depending on what I add…
Basically Mono.Cecil adds a jump out of the method.


Which in short leads to broken assemblies:

[IL]: Error: [C:\…\Tedd.Fibres\Tedd.Fibres.Test.GUI\bin\Debug\Tedd.Fibres.TestModule_out.dll : Tedd.Fibres.TestModule.TestClass::Test][offset 0x00000028] Branch out of the method.

I managed to Google some other people having the same problem, and Mono.Cecil doesn’t seem to be under active development for the past 3 years or so… Hmm…. :/

UPDATE: This is not a bug!
As the good Jb Evain explained, simply add method.Body.Simplify() before and method.Body.Optimize() after the method processing and it works fine.

One thought on “Bug in Mono.Cecil

  1. Jb Evain

    Cecil is being developed and maintained. And the bug is not directly in Cecil, but in how you use it. You’re injecting code inside a branch which is a short form, and hence the offset offerflows. Call .Simplify () on the MethodBody before instrumenting it, and call Optimize () on it when you’re done. Here, the «bug» is gone.


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