> This logic works fine - except when gcc tells me that this sibcall > function is a leaf, despite the fact that it calls out to another function > that probably clobbers the call_used regs.
A leaf function is one that doesn't make any function calls. Technically speaking, a sibcall isn't really a function call, it's "returning" to somewhere other than the caller. For most purposes it's as if foo4's caller made the function call, not foo4. As you say, the correct solution is to disallow sibcalls on isr routines. Paul
