src: emit warnings from V8

[devsnek]

Currently the only place V8 does this is asm.js compilation:

function AsmModule() {
  'use asm';

  function add(a, b) {
    a = a | 0;
    b = b | 0;

    // should be `return (a + b) | 0;`
    return a + b; // (node:18940) V8: test.js:9 Invalid asm.js: Invalid return type
  }

  return { add: add };
}

In chromium:

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• commit message follows commit guidelines

[nodejs-github-bot]

@devsnek build started: https://ci.nodejs.org/blue/organizations/jenkins/node-test-pull-request-lite-pipeline/detail/node-test-pull-request-lite-pipeline/1610/pipeline

[targos]

Is it testable? Maybe with a message test?

[addaleax]

Would you mind adding the test case from the PR description as a test here?

[devsnek]

@targos @addaleax tests added 👍

[devsnek]

CI https://ci.nodejs.org/job/node-test-pull-request/18610/

[refack]

👍

[refack]

refack added the wasm label

_{I know it's not wasm but it's the most relevant label.}

[joyeecheung]

It would probably be even better if ProcessEmitWarningGeneric is less generic on the C++ side and we can just do the overload in JS...but anyway LGTM

(off-topic: we have a wasm label? AND a asm.js label? and they are both green?)

[refack]

a wasm label? AND a asm.js label? and they are both green

The asm.js is brand new. And like their subjects, if you look from a distance they look the same ;)

[devsnek]

CI https://ci.nodejs.org/job/node-test-pull-request/18619/

[codebytere]

@devsnek do you think that this can/should be backported to v10.x? I added the label but feel free to remove!