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// run-pass
#![allow(dead_code)]
// check that we don't have linear stack usage with multiple calls to `push`
#![feature(test)]
extern crate test;
use std::mem;
fn meal() -> Big {
if test::black_box(false) {
panic!()
}
Big { drop_me: [
None, None, None, None, None, None, None, None,
None, None, None, None, None, None, None, None,
None, None, None, None, None, None, None, None,
None, None, None, None, None, None, None, None,
None, None, None, None, None, None, None, None,
None, None, None, None, None, None, None, None,
]}
}
pub struct Big {
drop_me: [Option<Box<u8>>; 48],
}
#[inline]
fn push(out: &mut Vec<Big>) {
out.push(meal());
}
#[inline(never)]
pub fn supersize_me(out: &mut Vec<Big>) {
push(out);
push(out);
push(out);
push(out);
push(out);
push(out);
push(out);
push(out);
push(out);
push(out);
push(out);
push(out);
push(out);
push(out);
push(out);
push(out); // 16 calls to `push`
verify_stack_usage(out);
push(out);
push(out);
push(out);
push(out);
push(out);
push(out);
push(out);
push(out);
push(out);
push(out);
push(out);
push(out);
push(out);
push(out);
push(out);
push(out); // 16 calls to `push`
}
#[inline(never)]
fn verify_stack_usage(before_ptr: *mut Vec<Big>) {
// To check stack usage, create locals before and after
// and check the difference in addresses between them.
let mut stack_var: Vec<Big> = vec![];
test::black_box(&mut stack_var);
let stack_usage = isize::abs(
(&mut stack_var as *mut _ as isize) -
(before_ptr as isize)) as usize;
// Give space for 2 copies of `Big` + 272 "misc" bytes
// (value observed on x86_64-pc-windows-gnu).
if stack_usage > mem::size_of::<Big>() * 2 + 272 {
panic!("used {} bytes of stack, but `struct Big` is only {} bytes",
stack_usage, mem::size_of::<Big>());
}
}
pub fn main() {
let mut v = vec![];
test::black_box(&mut v);
supersize_me(&mut v);
}
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