This is a question that has bothered me for more than twenty-five years. Blame it on my being one of those forthies, I guess. Recent posts encourage me to ask again.
Is there any good reason for interleaving the return addresses with data on the data/parameter stack in C? I know it's the tradition, from back when it was all we could hope for to have one page per process, but that has not been the case for many years, I think. Adding code to the program preamble to reserve space for another stack with mmap shouldn't be hard at all. Default address separation of about a quarter to a half a gig should be reasonable in 32 bit address space, at any rate. New compiler switches would be needed to tune the separation. I'm pretty sure openbsd has the means to keep a largish no-access region between the stacks. The call protocol itself should be simpler, although I might expect some debate about which stack to push frame pointers to when pushing frame pointers. The problem, I think, is in convincing the compiler to refrain from moving the frame pointer to the stack pointer on function entry. Maybe. To those on the list who are intimate with the compiler(s), how difficult would it be to change the function call protocol to push the program counter to a separate stack from the parameters and locals? Or am I speculating about a different world, still? Joel Rees Computer memory is just fancy paper, CPUs just fancy pens. All is a stream of text flowing from the past into the future.
