Bug 52489 - ilasm fails with "Circular definition of class" for Generic Singleton<T> designs
Summary: ilasm fails with "Circular definition of class" for Generic Singleton<T> designs
Status: NEW
Alias: None
Product: Compilers
Classification: Mono
Component: IL assembler ()
Version: unspecified
Hardware: PC Windows
: --- normal
Target Milestone: ---
Assignee: Bugzilla
: 8745 ()
Depends on:
Reported: 2017-02-14 03:25 UTC by pushedx
Modified: 2018-01-10 02:11 UTC (History)
3 users (show)

Is this bug a regression?: ---
Last known good build:

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Description pushedx 2017-02-14 03:25:23 UTC

This bug had been previously filed on the Novell bugtracker a long time ago, but has not been fixed or migrated to this bugtracker since: https://bugzilla.novell.com/show_bug.cgi?id=443159

I added a few extra key words to the Summary for search visibility, as the Singleton pattern is just one example of where this bug happens in practice when round-tripping mono assemblies.

[Steps to Reproduce]

-- Program.cs --

namespace bug_report_generic_self
	public class Singleton<T> { }

	public class TestClass : Singleton<TestClass> { }

	class Program
		static void Main(string[] args)
			var obj = new TestClass();

-- Example disasm generation (note: I used msvc to compile the exe for simplicity) --

ikdasm.exe bug_report_generic_self.exe /OUT=bug_report_generic_self.il /COMPAT=2.0


-- Example (mono) ilasm generation

ilasm.exe /exe /output:bug_report_generic_self_ilasm.exe bug_report_generic_self.il

	Assembling 'bug_report_generic_self.il' , no listing file, to exe --> 'bug_report_generic_self_ilasm.exe'

	bug_report_generic_self.il : Error : Circular definition of class: bug_report_generic_self.TestClass

	***** FAILURE *****

[Expected Results]

For this code scenario to be handled correctly like .Net's ilasm does.

[Additional Information]

I cloned mono master earlier today, because I needed some other fixes in ilasm that are not in Releases, and followed the "http://www.mono-project.com/docs/compiling-mono/windows" guide to get all this setup.

$ git log -1
commit 9433d2c80a59f54cb43452adfe49a9c2a3a674d1
Author: <removed>
Date:   Mon Feb 13 09:56:11 2017 -0500

    Bump bockbuild

Just including that information for completeness though, as the issue has been around for so long it's not specific to anything new.

I really would like to implement a solution for this myself, but I don't understand what actually needs to be done to solve the circular definition lookup. I tried adding in a parent-less type definition, resolved the parent, remove the parent-less type definition, and continue, but that didn't work because I'd also need to modify PEAPI as well to remove the temp definition, and then re-fix the referenced type. That seemed a bit convoluted, so I was hoping there'd be a better way.
Comment 1 Alexander Köplinger [MSFT] 2018-01-10 02:11:08 UTC
Given the age of the issue it probably won't show up on our radar anytime soon so a community fix would be greatly appreciated :)

I'd reach out to the mono-devel mailing list for questions (https://lists.dot.net/mailman/listinfo/mono-devel-list).
Comment 2 Alexander Köplinger [MSFT] 2018-01-10 02:11:14 UTC
*** Bug 8745 has been marked as a duplicate of this bug. ***