线程“<main>"使用 Box 分配大数组时堆栈溢出 [英] Thread '<main>' has overflowed its stack when allocating a large array using Box

问题描述

我正在实施 combsort.我想在堆栈上创建固定大小的数组，但它显示 stack overflow.当我将它更改为在堆上时(Rust by Example 说 在堆中分配我们必须使用 Box)，还是显示stack overflow.

I'm implementing combsort. I'd like to create fixed-size array on the stack, but it shows stack overflow. When I change it to be on the heap (Rust by Example says to allocate in the heap we must use Box), it still shows stack overflow.

fn new_gap(gap: usize) -> usize {
    let ngap = ((gap as f64) / 1.3) as usize;
    if ngap == 9 || ngap == 10 {
        return 11;
    }
    if ngap < 1 {
        return 1;
    }
    return ngap;
}

fn comb_sort(a: &mut Box<[f64]>) {
    // previously: [f64]
    let xlen = a.len();
    let mut gap = xlen;
    let mut swapped: bool;
    let mut temp: f64;
    loop {
        swapped = false;
        gap = new_gap(gap);
        for i in 0..(xlen - gap) {
            if a[i] > a[i + gap] {
                swapped = true;
                temp = a[i];
                a[i] = a[i + gap];
                a[i + gap] = temp;
            }
        }
        if !(gap > 1 || swapped) {
            break;
        }
    }
}

const N: usize = 10000000;

fn main() {
    let mut arr: Box<[f64]> = Box::new([0.0; N]); // previously: [f64; N] = [0.0; N];
    for z in 0..(N) {
        arr[z] = (N - z) as f64;
    }
    comb_sort(&mut arr);
    for z in 1..(N) {
        if arr[z] < arr[z - 1] {
            print!("!")
        }
    }
}

输出:

thread '<main>' has overflowed its stack
Illegal instruction (core dumped)

或

thread 'main' has overflowed its stack
fatal runtime error: stack overflow

我知道我的堆栈大小不够，在创建一个函数内部太大的非堆数组时与C++相同，但是这段代码使用了堆但仍然显示堆栈溢出.这段代码到底有什么问题?

I know that my stack size is not enough, the same as C++ when creating a non-heap array that is too big inside a function, but this code is using heap but still shows stack overflow. What's really wrong with this code?

推荐答案

据我所知，似乎该代码仍在尝试先在堆栈上分配数组，然后再将其移入框中.

As far as I can tell, it seems like that code is still trying to allocate the array on the stack first, and then move it into the box after.

如果我像这样切换到 Vec 代替 Box<[f64]> 对我有用:

It works for me if I switch to Vec<f64> in place of Box<[f64]> like this:

fn new_gap(gap: usize) -> usize {
    let ngap = ((gap as f64) / 1.3) as usize;
    if ngap == 9 || ngap == 10 {
        return 11;
    }
    if ngap < 1 {
        return 1;
    }
    return ngap;
}

fn comb_sort(a: &mut [f64]) {
    // previously: [f64]
    let xlen = a.len();
    let mut gap = xlen;
    let mut swapped: bool;
    let mut temp: f64;
    loop {
        swapped = false;
        gap = new_gap(gap);
        for i in 0..(xlen - gap) {
            if a[i] > a[i + gap] {
                swapped = true;
                temp = a[i];
                a[i] = a[i + gap];
                a[i + gap] = temp;
            }
        }
        if !(gap > 1 || swapped) {
            break;
        }
    }
}

const N: usize = 10000000;

fn main() {
    let mut arr: Vec<f64> = std::iter::repeat(0.0).take(N).collect();
    //let mut arr: Box<[f64]> = Box::new([0.0; N]); // previously: [f64; N] = [0.0; N];
    for z in 0..(N) {
        arr[z] = (N - z) as f64;
    }
    comb_sort(arr.as_mut_slice());
    for z in 1..(N) {
        if arr[z] < arr[z - 1] {
            print!("!")
        }
    }
}

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