I am not familar what exactly to do to compile 64Bit app/plugin on MAC. From my understanding a univrsal binary (Intel 32/64) does already include a 64Bit version, right? Do I need to compile a 64Bit version then in addition or is a universal binar 32/64 enough?


Thank you!

The universal binary should be what you need.  

(I stick a check in my build script to make sure I've actually got a universal binary each time.  The number of times I've thought I had one, but had accidentially changed a setting somewhere ...)

If You make some plugins. You can easly check if You perform correct setting (universal binary 32/64) when You run 32 and than 64 bit host. I always check differences in Reaper 32 and 64. If Your plugin have only one architecture than You'll see it in plugin list.
For example:

I compile my plugin as 32 bit bundle.
When I open 32 reaper I will see plugin name on the list :  "myplugin.vst"
When I open 64 reaper I will see : "myplugin.vst (x86)"

Thank you!  I finally made my way into the 64Bit world and managed to compile both, 32 and 64Bit versions of my plugin.

For 32Bit I've used the universal binary, for 64Bit I set the project settings to 64Bit. Reason why I did that was just because

Reaper64 didn't find the universal binary. But now, after reading your comments I may have to review this :-)

Anyway, my beta tester were all able to load the plugin successfully except one issue with Multiclient driver but I will open a new thread for this.

Thanks again!