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To me it just seems that you're arguing semantics... The most important type of argument to have. If you don't agree on semantics, no other discussion is worth

To me it just seems that you're arguing semantics... The most important type of argument to have. If you don't agree on semantics, no other discussion is worth having, as you will never know if the other party actually agrees with you or not. I mean, what is the difference between "stack memory" and "heap memory allocated to store the stack", other than the fact that the OS preallocates the first one for you by default? That is a pretty major difference with wide-ranging effects on program performance right there. To me, "the stack" and "a stack-like data structure stored in the heap that is used as a stack to replace what would otherwise be the stack" is functionally the same thing... System-level error messages and memory managers both disagree. You know that (given appropriate conditions) you can just allocate stack frames wherever you want and point your stack pointer to whatever you want, whenever you want, right? Yes. And once you do, that memory becomes functionally privileged from the perspective of your allocation strategy. This is what the Go compiler does to prevent Go programs from running out of the stack space provided by the OS by default. But AFAIK they don't advertise that Go programs use constant stack space and you don't have to worry about out-of-stack issues... Of course not. Because they actually use that space as stack space, to store function activation records.

wizeman 6y ago
> That is a pretty major difference with wide-ranging effects on program performance right there. It really isn't. The only difference is that in the second case you have to call mmap() at the beginning of your program to allocate stack space and then change the stack pointer to point to it, the rest of the execution would remain the same. > That is a pretty major difference with wide-ranging effects on program performance right there. > And once you do, that memory becomes functionally privileged from the perspective of your allocation strategy. So you're saying that the transformation you mentioned gives you better error messages at the expense of performance, because now instead of using the stack, you have to keep allocating a stack-like structure on the heap? If so, that's not entirely true, as you can have the same error messages without doing this transformation (that's why some kernels and runtimes can detect stack overflow and even resize the stack), so the only observable functional difference is that you replace a simple stack-like allocation mechanism with one that is slower without much benefit. And it would still be a bit disingenuous to say that the transformation would make your program use constant stack space, as if replacing stack space with heap space somehow makes stack usage on a recursive function irrelevant...

wizeman 6y ago

> That is a pretty major difference with wide-ranging effects on program performance right there. It really isn't. The only difference is that in the second case you have to call mmap() at the beginning of your program to allocate stack space and then change the stack pointer to point to it, the rest of the execution would remain the same. > That is a pretty major difference with wide-ranging effects on program performance right there. > And once you do, that memory becomes functionally privileged from the perspective of your allocation strategy. So you're saying that the transformation you mentioned gives you better error messages at the expense of performance, because now instead of using the stack, you have to keep allocating a stack-like structure on the heap? If so, that's not entirely true, as you can have the same error messages without doing this transformation (that's why some kernels and runtimes can detect stack overflow and even resize the stack), so the only observable functional difference is that you replace a simple stack-like allocation mechanism with one that is slower without much benefit. And it would still be a bit disingenuous to say that the transformation would make your program use constant stack space, as if replacing stack space with heap space somehow makes stack usage on a recursive function irrelevant...