V9020

Code

V9020

Message

VM call frame stack has no frame where the dispatch loop requires one

The VM needed the topmost call frame and the call frame stack was empty. The dispatch loop stores the program counter back into the topmost frame after each instruction and before a call, and pops that frame on a return. It runs only while a frame is live, so an empty frame stack at one of those points means the VM broke its own invariant: no program, well-formed or not, is expected to cause it. The VM halts the program rather than continue with no frame to execute.

This error should not occur during normal operation. It indicates a bug in the IronPLC compiler or VM.

Report this as a bug at https://github.com/ironplc/ironplc/issues with the .iplc file and the source program that produced it.

Think IronPLC is wrong about this?

If you believe this diagnostic is incorrect, open an issue on GitHub with a small sample that demonstrates the problem.