App exited with exit code 1 - what does it mean and what causes it?

Bodevinaat

Can't find that in the documentation and the debugger is not able to catch it.

Bodevinaat

You can see the actual error on de </> pane. In my case:

Fatal VM exception: System.InvalidCastException: Expected Class but got DateTime
.                                                                                                                                                                                                                                                    at Objo.VM.Value.ThrowInvalidCast(ObjoType expected)
   at Objo.VM.Value.get_AsClass()
   at Objo.VM.VM.Run(Int32 exitAtFp)
   at Objo.VM.VM.Execute(ObjoClosure closure, VMExecutionEntryPoint entryPoint)
   at Objo.Host.Desktop.Program.<>c__DisplayClass0_0.<Main>b__5()
[Runtime Error] App exited with code 1.

Still hard to find where the error is actually located...

Syntec

Bodevinaat I had something similar, App exited with exit code 1, it turned out to be a For loop structure below

Var x As Integer = 0 To Width
# Do something
Next

Width was a double, the debugger didn't catch it and it exits with code 1.

I believe some type exception catching needs to be tightened up. Honestly if you didn't write too much code before this error popped up, put a break point at the new code and look for the exact line that is causing the crash and look for a type cast mismatch.

bgrommes

Some dialects of Basic would truncate or round a double implicitly and otherwise strive to "help" the developer in situations like this, but this is a strongly typed dialect that shouldn't do that. Width As Double should be illegal and should be caught at compile time (by which I really mean, in real time by the Analyser when you are writing the code).

Garry

Thanks. I’ve identified and fixed two problems here for the next release:

https://feedback.objo.dev/bug/1187

https://feedback.objo.dev/bug/1188

The For x As Integer = 0 To Width case is confirmed: Width is a Double, but the compiler was allowing it into an Integer loop and the VM then failed internally. This will now produce a clear compile-time error. Integer(Width) can be used when truncation is intentional.

I’ve also fixed the VM error handling so an unexpected mismatch such as Expected Class but got DateTime reports the failing Objo source line and call stack instead of only “exit code 1”.

The DateTime error appears to have a separate underlying cause. Could you please provide:

Your exact Objo Studio version and operating system.
The smallest project or source that still reproduces the problem.
Whether it happens with Run, Debug, or both.
Whether any watches, watchpoints, or conditional breakpoints are enabled—and whether disabling them changes the result.
The complete contents of the </> output pane and the steps needed to trigger the failure.

Please remove any private data or API keys before attaching the project.

Bodevinaat

Hi Garry,
enclosed my app. I stripped all unnecessary code. I normally use the GIT repo but saved this one as .objo.
I'm running 26.8.3 and I get the error in both Windows 11 and macOS 26.5.2

urenregistratie.objo

5kB

It happens with Run and Debug. Enabling watchpoints makes no difference. The debugger isn't able to catch this error.

Fatal VM exception: System.InvalidCastException: Expected Class but got DateTime
.                                                                                                                                                                                                                                                    at Objo.VM.Value.ThrowInvalidCast(ObjoType expected)
   at Objo.VM.Value.get_AsClass()
   at Objo.VM.VM.Run(Int32 exitAtFp)
   at Objo.VM.VM.Execute(ObjoClosure closure, VMExecutionEntryPoint entryPoint)
   at Objo.Host.Desktop.Program.<>c__DisplayClass0_0.<Main>b__5()
[Runtime Error] App exited with code 1.

Just running the program is enough to trigger the failure.

Garry

Thank you. The supplied project was exactly what I needed to identify the cause.

The problem is this declaration directly inside HourEntryContainer:

Var ThisWeek As DateTime = DateTime.Now

Class data in Objo must be declared using Property; Var is for local variables and module members. In this project, ThisWeek is already declared locally inside FakeOpening(), so the class-level declaration can simply be removed.

The compiler had a bug where it accepted this invalid class member and generated incorrect initialisation bytecode. That ultimately caused the application to exit with code 1. The earlier fixes exposed the underlying internal type mismatch, which made this much easier to diagnose.

This compiler bug is now fixed: https://feedback.objo.dev/bug/1196

In the next release, the same code will produce a clear compile-time error:

Class fields must use 'Property' instead of 'Var'.

If persistent class state was intended, the alternative is:

Private Property ThisWeek As DateTime

and then assign DateTime.Now inside a method such as FakeOpening(), since runtime expressions cannot be used as property defaults.

Thanks again for providing the complete project - it was extremely helpful.