How to protect extension against compilation ?

It generates an exception. Basically it crashes the application, that's what the VC debugger does when you set a break point (it replaces the current instruction by an int 3). As the exceptions are filtered in the calling routine (the MMF2 Build routine), the program doesn't crash and the build is stopped.

Wow ! Ok. :)

So maybe it could be nice to add this tip in SDK by default for Edit-time version of extensions ? Because, some extensions are actually released without runtime version...