Hi, I've pretty much hit a wall on this, so I will have to ask for help now. The attached is what I have so far in my attempt to frame-ify avr-tdep.c. As it stands, things kinda work. I can 'step' around a program fine. Things go wrong as soon as I try to 'next' over a function call, gdb goes into an infinite loop. If I 'step' down into a function called from main(), a backtrace never gets me back to main. Here's a dump of the backtrace output (I'll forego the infinite loop output to save some bandwidth 8-): func1 () at tst.c:23 23 struct cc var = {0}; /* This uses memset()! */ (gdb) bt #0 func1 () at tst.c:23 { get_prev_frame (this_frame=0) { frame_id_p (l={stack=0x8010f9,code=0xd0}) -> 1 } { frame_register_unwind (frame=0,regnum="PC",...) { frame_register_unwind (frame=-1,regnum="PC",...) -> *optimizedp=0 *lvalp=2 *addrp=0x23 *bufferp=[fffffff0000000] } -> *optimizedp=0 *lvalp=2 *addrp=0x23 *bufferp=[fffffff0000000] } { frame_pc_unwind (this_frame=0) -> 0xf0 } -> {level=1,type=UNKNOWN_FRAME,unwind=,pc=0xf0,id=,func=} } #1 0x000000f0 in func1 () at tst.c:22 { get_prev_frame (this_frame=1) { get_frame_id (fi=1) { frame_func_unwind (fi=0) -> 0xd0 } Sending packet: $md0,27#96...Ack Packet received: cf92df92ef92ff920f931f93cf93df93cdb7deb726970fb6f894debf0fbecdbf86e0fe01319611 Sending packet: $mf7,11#98...Ack Packet received: 928a95e9f719821a82ed80fe80cc24dd24 { frame_register_unwind (frame=0,regnum="r28",...) Sending packet: $m801100,1#f4...Ack Packet received: 00 -> *optimizedp=0 *lvalp=1 *addrp=0x801100 *bufferp=[00] } { frame_register_unwind (frame=0,regnum="r29",...) Sending packet: $m801101,1#f5...Ack Packet received: 00 -> *optimizedp=0 *lvalp=1 *addrp=0x801101 *bufferp=[00] } { frame_id_eq (l={stack=0x8010f9,code=0xd0},r={stack=0x80000e,code=0xd0}) -> 0 } -> {stack=0x80000e,code=0xd0} } { frame_id_p (l={stack=0x80000e,code=0xd0}) -> 1 } { frame_id_inner (l={stack=0x80000e,code=0xd0},r={stack=0x8010f9,code=0xd0}) -> 1 } This frame inner-to next frame (corrupt stack?) (gdb) I'm pretty confused as to how frames are getting chained up and unwound. I suspose that I'm not thinking about the the SP in the proper manner in relation to the frames. Could some kind soul lend me some insight? Thanks. Ted Roth