I'm still totally not understanding your claim that call/cc should have the same overhead as an ordinary function call.
I read the Clinger "Implementation Strategies for Continuations" paper and they found call/cc about 10 times slower than function calls on the tak/ctak tests. I tried those tests on PLT Scheme and the overhead I saw is even worse: .7 seconds with function calls vs 51.8 seconds with continuations on (tak 24 16 8).
Clinger says about the stack strategy: "When a continuation is captured, however, a copy of the entire stack is made and stored in the heap. ... Variations on the stack strategy are used by most implementations of Scheme and Smalltalk-80."
Components of function call: (1) put arguments somewhere (2) put return address somewhere (3) jump to function.
Components of call/cc: (1) put return address as argument somewhere (2) put return address somewhere (3) jump to function.
That said, continuations generally assume that "put X somewhere" means somewhere != stack. Yes, even return addresses are not intended to be on the stack when using continuations. The main problem is when compiling down to C, which always assumes that somewhere == stack. If you're compiling down to machine language where you have access to everything, then you can just ignore the stack, but not in C, which inherently expects the stack.
