PSA: Increase your stack size before the Meta Hacker Cup, here's how

This post was originally written on Codeforces; relevant discussion can be found here.

Disclaimer: Please verify that whichever of the following solutions you choose to use indeed increases the stack limit for the execution of the solution, since different OSes/versions can behave differently.

On Linux (and probably MacOS), running ulimit -s unlimited in every instance of the shell you use to execute your program will work just fine (assuming you don’t have a hard limit). On some compilers, passing -Wl,--stack=268435456 to the compiler options should give you a 256MB stack.

But a much easier way from my comment a couple of years ago, originally from here, is to do this in your Meta Hacker Cup template:

#include <bits/stdc++.h>
using namespace std;
void main_() {
    // implement your solution here
}
static void run_with_stack_size(void (*func)(void), size_t stsize) {
    char *stack, *send;
    stack = (char *)malloc(stsize);
    send = stack + stsize - 16;
    send = (char *)((uintptr_t)send / 16 * 16);
    asm volatile(
        "mov %%rsp, (%0)\n"
        "mov %0, %%rsp\n"
        :
        : "r"(send));
    func();
    asm volatile("mov (%0), %%rsp\n" : : "r"(send));
    free(stack);
}
int main() {
    run_with_stack_size(main_, 1024 * 1024 * 1024); // run with a 1 GiB stack
    return 0;
}

It apparently works with Windows as well, as a commenter confirmed, and I believe it should work with MacOS as well.

UPD: To use this on 32 bit systems/compilers, replacing %rsp with %esp works. I haven’t tried changing this for ARM, so any solutions which do the same thing for ARM would be appreciated.