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    <p>If one is debugging, not all optimizations need to be turned on unless you are debugging the optimization itself. So tail recursion optimization (TRO) doesn't have to disable backtraces during debugging unless the development environment is braindead (eg., doesn't have a "disable optimizations" option). </p> <p>The <em>space</em> occupied by the metadata if you did record it is pretty small; basically its says, "a recursive call was made". A linked list with elements of a small number of bytes would do the trick. But I don't think it would make sense to record backtrace metadata in the face of TRO; if you are optimizing, you probabaly don't want to pay the extra time cost of recording the metadata, either, just because somebody <em>might</em> want to debug later. </p> <p>I'm not sure what <em>you</em> mean by "minimize the size of stack frame" since you ask in the context of TRO. In general, a good compiler will minimize the size by automatically by only assigning enough space to do the the entire computation of the (sub)routine which the stack frame instance represents. One standard optimization is letting variables with non-overlapping lifetimes share the same space in the stack frame. One can do this a couple of different ways: a) nested scopes inside the body of the subroutine which don't overlap can trivially share their space in a stack-like discipline, and b) treating the "stack frame" not so much as a stack, but as a bunch of registers for storing spilled values; a register coloring algorthim can handle this pretty nicely.</p> <p>Sometimes stack frame minimization is damaged by the (lack of) support by the OS. See <a href="https://stackoverflow.com/q/994555/120163">this</a> for a discussion of how Windows traps damage stack frame size considerably.</p>
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    1. POStack traces vs. TCO: Do non-tail recursive languages generally have efficient stack frames?
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    1. CO+1 That's a very interesting link. I find it weird that Windows would push the CPU context on the user-mode stack, though -- shouldn't it be pushed on the kernel-mode stack? What if the stack pointer is bad -- would the system then crash?
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    2. CO@Mehrdad: It makes sense that the full process context is stored in the user space, especially since one can write user trap routines to inspect/modify/restart after a trap. (We do this for divide-by-zero traps, etc. in our PARLANSE language). What is stupid is pushing it into the user stack; my point was that the application could tell the OS where to put trap data (including the stack for backwards compatibility) to avoid this rediculous demand on stack frame size. ...
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    3. CO@Mehrdad: ... Regardless, if the SP is bad and a trap occurs, presumably the hardware produces a "Double Fault" and Windws simply aborts your process. If the SP is good to take the hardware-pushed trap data, but not enough space remains to hold the additional stuff MS pushes, yes, Windows might crash; presumably MS thought about (or experienced) this and has a defense.
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