[anyfoo]

That seems to be what -fstack-check for gcc is doing:

"If neither of the above are true, GCC will generate code to periodically “probe” the stack pointer using the values of the macros defined below."[1]

I guess I'm wondering why this isn't always on if it solves the problem with negligible cost? Genuine question, not trying to make a point.

[1] https://gcc.gnu.org/onlinedocs/gccint/Stack-Checking.html

[Dylan16807]

What I'm finding in a quick search is:

* It should be fast, but I haven't found a benchmark.

* There appear to be some issues of signals hitting at the wrong time vs. angering valgrind, depending on probe timing.

* Probes like this are mandatory on windows to make sure the stack is allocated, so it can't be that bad.

[anyfoo]

I'm mostly interested in it for kernel code though, so the second point at least does not apply, at least not directly. Maybe there is something analogous when preempting kernel threads, I haven't thought it through at all. But interesting.

[Joker_vD]

Because it's on by default in MSVC [0], and we all know that whatever technical decisions MS makes, they're superior to whatever technical decision the GNU people make. /s

Speaking seriously, I too would like an answer.

[0] https://docs.microsoft.com/en-us/windows/win32/devnotes/-win...

[pjmlp]

One decision Microsoft made was not to support VLAs at all, even after their new found C love.