chore: add test to demonstrate PrevRealm var block bug

[n0izn0iz]

This adds a test to demonstrate the PrevRealm bug in var block outlined in #941

• Added new tests, or not needed, or not feasible
• Provided an example (e.g. screenshot) to aid review or the PR is self-explanatory
• Updated the official documentation or not needed
• No breaking changes were made, or a BREAKING CHANGE: xxx message was included in the description
• Added references to related issues and PRs
• Provided any useful hints for running manual tests
• Added new benchmarks to generated graphs, if any. More info here.

[tbruyelle]

thanks for the issue and the PR, it would be nice if your test reports something like

Suggested change

	t.Errorf("initRealm != varRealm")
	t.Errorf("expect initRealm '%s' to be equal to varRealm '%s'", initRealm.Addr(), varRealm.Addr() )

Same for following t.Errorf, thanks in advance!

[n0izn0iz]

done

[tbruyelle]

I put some logs in std.PrevRealm and the issue is because then test.GetPrevRealm() is invoked inside var (), the frames doesn't contain gno.land/r/demo/bugs/var_prev_realm. It contains only a single frame, which is gno.land/r/demo/tests. Because of that, test.GetPrevReam() returns the user address.

I assume it's something that needs to be fixed in the gnovm, so probably a little tricky!

[moul]

@tbruyelle do you think we can use the txtar stuff for storing known bugs in the repo somewhere?

[tbruyelle]

@tbruyelle do you think we can use the txtar stuff for storing known bugs in the repo somewhere?

Ideally it should go to gnovm/tests/challenges but it's not possible since gno.land/r/demo/tests is required and isn't available for the challenges.

Else txtar can be used also, it just need a proper setup for this kind of bugs.

[n0izn0iz]

if other challenges realms are available I could add two realms in challenges

[tbruyelle]

if other challenges realms are available I could add two realms in challenges

I'm not sure you can interact with more than one realm in the challenges, but maybe that's possible. The code is in gnovm/tests/file_test.go#TestChallenges if you want to have a look.

[leohhhn]

closing as #941 has been resolved.