I'm in the process of migrating an Objective-C project to MacRuby (0.5 trunk) and am seeing this error when I run the application: *Assertion failed: (castIsValid(getOpcode(), S, Ty) && "Illegal SExt"), function SExtInst, file Instructions.cpp, line 2508.* * * The stack looks like this: ** * #0 0x9870d912 in __kill #1 0x9870d904 in kill$UNIX2003 #2 0x987a0b99 in raise #3 0x987b6c50 in abort #4 0x987a37f8 in __assert_rtn #5 0x0090ab1a in llvm::SExtInst::SExtInst #6 0x001528b3 in RoxorCompiler::compile_conversion_to_ruby #7 0x00158847 in RoxorCompiler::compile_stub #8 0x0017e173 in RoxorCore::gen_stub #9 0x0018b4cd in rb_vm_dispatch #10 0x00e432a2 in ?? #11 0x0004c2cb in ruby_run_node #12 0x00186a61 in macruby_main #13 0x00002c64 in main at main.m:13 I was following the (admittedly quite old) page covering this sort of activity at http://www.macruby.org/trac/wiki/MacRubyFromObjC. My main.m and rb_main.rb are vanilla and copied from the FlickrDemo (which runs on my system). If I reduce rb_main.rb to the bare minimum of the following, I still get the error. framework 'Cocoa' NSApplicationMain(0, nil) I'm assuming it's something in my ObjC code that is causing the problem -- is there a good way to zero in on it? My llvm and MacRuby knowledge is pretty rough, so I'm not sure where to drop breakpoints. If there's a "don't use <datatype>" rule of thumb, that would be great, too, as that appears to be where things may be hung up. Thanks! -a. *