生成返回字符串的函数时，为啥 wasm-opt 在 wasm-pack 构建中失败？

Posted 2023-02-19

【中文标题】生成返回字符串的函数时，为啥 wasm-opt 在 wasm-pack 构建中失败？

【英文标题】：Why does wasm-opt fail in wasm-pack builds when generating a function returning a string?生成返回字符串的函数时，为什么 wasm-opt 在 wasm-pack 构建中失败？

【发布时间】：2021-02-06 23:22:50

【问题描述】：

我正在处理Rust WASM tutorial for Conway's game of life。

文件中最简单的函数之一称为Universe.render（它用于渲染表示游戏状态的字符串）。当我运行wasm-pack build 时，它会导致错误：

Fatal: error in validating input
Error: failed to execute `wasm-opt`: exited with exit code: 1
  full command: "/home/vaer/.cache/.wasm-pack/wasm-opt-4d7a65327e9363b7/wasm-opt" "/home/vaer/src/learn-rust/wasm-game-of-life/pkg/wasm_game_of_life_bg.wasm" "-o" "/home/vaer/src/learn-rust/wasm-game-of-life/pkg/wasm_game_of_life_bg.wasm-opt.wasm" "-O"
To disable `wasm-opt`, add `wasm-opt = false` to your package metadata in your `Cargo.toml`.

如果我删除该函数，则代码构建不会出错。如果我用以下函数替换它，构建会失败并出现同样的错误：

pub fn wtf() -> String 
    String::from("wtf")

似乎任何返回 String 的函数都会导致此错误。为什么？

以下是我的全部代码：

mod utils;

use wasm_bindgen::prelude::*;

// When the `wee_alloc` feature is enabled, use `wee_alloc` as the global
// allocator.
#[cfg(feature = "wee_alloc")]
#[global_allocator]
static ALLOC: wee_alloc::WeeAlloc = wee_alloc::WeeAlloc::INIT;

// Begin game of life impl

use std::fmt;

#[wasm_bindgen]
#[repr(u8)]
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum Cell 
    Dead = 0,
    Alive = 1,


#[wasm_bindgen]
pub struct Universe 
    width: u32,
    height: u32,
    cells: Vec<Cell>,


impl fmt::Display for Universe 
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result 
        for line in self.cells.as_slice().chunks(self.width as usize) 
            for &cell in line 
                let symbol = if cell == Cell::Dead  '◻'  else  '◼' ;
                write!(f, "", symbol)?;
            
            write!(f, "\n")?;
        

        Ok(())
    


impl Universe 
    fn get_index(&self, row: u32, column: u32) -> usize 
        (row * self.width + column) as usize
    

    fn live_neighbor_count(&self, row: u32, column: u32) -> u8 
        let mut count = 0;
        for delta_row in [self.height - 1, 0, 1].iter().cloned() 
            for delta_col in [self.width - 1, 0, 1].iter().cloned() 
                if delta_row == 0 && delta_col == 0 
                    continue;
                

                let neighbor_row = (row + delta_row) % self.height;
                let neighbor_col = (column + delta_col) % self.width;
                let idx = self.get_index(neighbor_row, neighbor_col);
                count += self.cells[idx] as u8;
            
        
        count
    


/// Public methods, exported to javascript.
#[wasm_bindgen]
impl Universe 
    pub fn tick(&mut self) 
        let mut next = self.cells.clone();

        for row in 0..self.height 
            for col in 0..self.width 
                let idx = self.get_index(row, col);
                let cell = self.cells[idx];
                let live_neighbors = self.live_neighbor_count(row, col);

                let next_cell = match (cell, live_neighbors) 
                    // Rule 1: Any live cell with fewer than two live neighbours
                    // dies, as if caused by underpopulation.
                    (Cell::Alive, x) if x < 2 => Cell::Dead,
                    // Rule 2: Any live cell with two or three live neighbours
                    // lives on to the next generation.
                    (Cell::Alive, 2) | (Cell::Alive, 3) => Cell::Alive,
                    // Rule 3: Any live cell with more than three live
                    // neighbours dies, as if by overpopulation.
                    (Cell::Alive, x) if x > 3 => Cell::Dead,
                    // Rule 4: Any dead cell with exactly three live neighbours
                    // becomes a live cell, as if by reproduction.
                    (Cell::Dead, 3) => Cell::Alive,
                    // All other cells remain in the same state.
                    (otherwise, _) => otherwise,
                ;

                next[idx] = next_cell;
            
        

        self.cells = next;
    

    pub fn new() -> Universe 
        let width = 64;
        let height = 64;

        let cells = (0..width * height)
            .map(|i| 
                if i % 2 == 0 || i % 7 == 0 
                    Cell::Alive
                 else 
                    Cell::Dead
                
            )
            .collect();

        Universe 
            width,
            height,
            cells,
        
    

    pub fn render(&self) -> String 
        self.to_string()
    

只需删除此文件底部的render 函数即可使构建成功。将render 函数替换为任何返回String 的函数会导致构建失败。为什么？

【问题讨论】：

由于这个问题只与wasm-opt当前版本中的错误有关，是否应该关闭这个问题？

这是一个很好的问题和一个很好的答案。从 github 问题来看，该错误已经存在了一段时间，尚未修复。您的回答可能会帮助其他人。

【参考方案1】：

事实证明这不是预期的行为；而不是 it is a bug 和 wasm-pack。

现在可以通过将以下内容添加到项目的cargo.toml 来解决此问题：

[package.metadata.wasm-pack.profile.release]
wasm-opt = ["-Oz", "--enable-mutable-globals"]