iPlug2 Forum

Question about building vst3 plugin with reaper

Hi all,
I’ve been using the iplug2 to build my custom vst3 plugin. I have an issue with debugging and testing. It seems that once I build the vst3 project, I need to close the reaper. Otherwise, the build will fail due to the failure of post-build.bat. It influences my productivity somehow. So, I wonder if there is any workaround for me to build the project but let the reaper open?

The problem is that when REAPER is open, REAPER is using your VST3 plugin. Windows knows this, and won’t let you overwrite the file while REAPER has it open, which is the correct thing to do. Changing a file like that out from under REAPER could crash it, depending on what the file is. So Windows prevents you from doing that.

The only way is to close REAPER and re-build. It MAY be possible to implement a REAPER-specific extension that would allow this to work, but that would be difficult, and require time that the devs need to put towards bug fixes and finalizing features.

That being said, I’ll put in a feature request for you, as I agree it’s a “nice-to have”. Maybe I can investigate making it work at a later date.

Apparently with Bitwig you can rebuild plugins without closing and reopening, since it runs the plugins in a different process. IIRC reaper can do that too, perhaps in that case it wouldn’t require closing and reopening reaper.

Possibly. The problem is that it’s still open in some process, and Windows doesn’t like people modifying binary files while they’re running. Give me a few minutes and I’ll see if I can test it.

Okay, I got it to work, sorta. First you have to go into Preferences and enable “Allow complete unload of VST plug-ins”. Once you do that, you’ll have to remove the plugin from REAPER before re-building the project. Then you can re-add the plugin. Given this, it would definitely be possible to make some sort of automation that would save your plugin state, unload it, run the build, then re-add the plugin. However, it’s more work than I’m willing to do right now. From my experience at least, REAPER loads pretty quickly, so it’s not an issue for me. Then again, I have a very fast computer, so it may be more of an issue for other people.


Thank you. That’s a pretty neat trick which resolves my problem