cooldome
commented
3 years ago I was thinking towards more general solution of extending Nim plugin infrastructure to be able to extend VM not just sempass. All done with hooks. Number of hooks available to plugin developers will extend with time. Sempass and VM for a start.
The idea that plugins should be as easy to use as:
nim --plugin:a,b,c
Nim uses standard library path resolution to find plugins a, b, c to compile them and load them before compiling your project.
Araq
github-actions[bot]
Nim VM Execute Loop Hooks
Abstract
Support hooking into the Nim VM execute loop, to enable things like suspend/resume, breakpoints and watches.
Motivation
Enu is a live-coding/IDE for game development in Nim that uses the VM extensively. I'm currently using a Nim fork to enable pausing and resuming script execution, and in the future I'd like to support breakpoints and watches.
Description
This needs consideration from people more knowledgable than myself, but I'm looking at providing 3 hooks:
enterHook- Run at the top of the interpreter loop. This could be used to bail out of the loop for breakpoints, or start a timer for profiling.leaveHook- Run at the bottom of the interpreter loop. This could be used to capture variable values for watches, and stop the profiling timer.exitHook- Run when the interpreter loop exits. This could be used to capture the stack and program counter, for suspend/resume support.The hooks should be inside
whenblocks, or some similar mechanism to ensure they have no performance cost if they're not being used.I have an initial implementation that is working for me for suspend/resume, but I haven't tried breakpoints or watches yet. It needs tests and docs, but I'll provide those if there's interest in merging it.
The cost to supporting this should be small, but it's also pretty ad-hoc, and requires a fair bit of work by the user to be used for anything useful. It would be better to spec out a real breakpoint/watchpoint/suspend/resume API, but I don't think I can take that on right now.