Question

我最近遇到了文章Tail call optimization in ECMAScript 6。我对测试TCO行为很感兴趣（尽管后来我发现文章提到的nodejs 8+不支持TCO），并且发现了我无法理解的行为。

普通循环功能

'use strict';

process.on('SIGTERM', () =>
{
    console.log('SIGTERM received');
    process.exit(0);
})

process.on('SIGINT', () =>
{
    console.log('SIGINT received');
    process.exit(0);
})

process.on('uncaughtException', (error) =>
{
    console.error('Uncaught exception', error);
    process.exit(1);
})

process.on('unhandledRejection', (error) =>
{
    console.error('Unhandled rejection', error);
    process.exit(0);
})

let counter = 0;

function test()
{
    console.log(`Counter: ${counter++}`);
    test();
}

console.log('Test started');

test();

console.log('Test ended');

此版本的代码产生：

Test started
Counter: 0
...
Counter: 10452
Uncaught exception RangeError: Maximum call stack size exceeded
    at WriteStream.removeListener (events.js:306:28)
    at write (console.js:130:12)
    at Console.log (console.js:135:3)
    at test (/test.js:31:13)
    at test (/test.js:32:5)
    at test (/test.js:32:5)
    at test (/test.js:32:5)
    at test (/test.js:32:5)
    at test (/test.js:32:5)
    at test (/test.js:32:5)
    at test (/test.js:32:5)
    at test (/test.js:32:5)
    at test (/test.js:32:5)
    at test (/test.js:32:5)
    at test (/test.js:32:5)
    at test (/test.js:32:5)

异步循环功能，功能内无任何等待

'use strict';

process.on('SIGTERM', () =>
{
    console.log('SIGTERM received');
    process.exit(0);
})

process.on('SIGINT', () =>
{
    console.log('SIGINT received');
    process.exit(0);
})

process.on('uncaughtException', (error) =>
{
    console.error('Uncaught exception', error);
    process.exit(1);
})

process.on('unhandledRejection', (error) =>
{
    console.error('Unhandled rejection', error);
    process.exit(0);
})

let counter = 0;

async function test()
{
    console.log(`Counter: ${counter++}`);
    test();
}

console.log('Test started');

test();

console.log('Test ended');

此版本的代码产生：

Test started
Counter: 0
...
Counter: 6967
Test ended

异步循环功能，该功能在功能内处于等待状态

'use strict';

const bluebird = require('bluebird');

process.on('SIGTERM', () =>
{
    console.log('SIGTERM received');
    process.exit(0);
})

process.on('SIGINT', () =>
{
    console.log('SIGINT received');
    process.exit(0);
})

process.on('uncaughtException', (error) =>
{
    console.error('Uncaught exception', error);
    process.exit(1);
})

process.on('unhandledRejection', (error) =>
{
    console.error('Unhandled rejection', error);
    process.exit(0);
})

let counter = 0;

async function test()
{
    await bluebird.delay(1);
    console.log(`Counter: ${counter++}`);
    test();
}

console.log('Test started');

test();

console.log('Test ended');

此版本的代码不间断运行。

摘要：

普通循环功能：在计数器10452处停止并抛出RangeError：超出了最大调用堆栈大小
该函数内没有任何等待的异步循环功能：在计数器6967处停止，没有任何错误
函数中具有await的异步循环功能：不间断运行

有人能解释这种行为差异或将我指向可以谷歌搜索的任何关键字吗？

对nodejs无限循环函数执行的奇怪观察

0 个答案: