:Ms2ger (he/him; ⌚ UTC+1/+2) Reporter
	Description • 6 years ago

Per spec: https://webassembly.github.io/spec/js-api/#dom-global-global step 3

Tested in:

wasm/jsapi/global/constructor.any.js

(which runs in jstests and wpt).

	Chris Mills [:cmills]
	Comment 1 • 6 years ago

Note for when I update the docs to account for this — If value is not specified, use a default value as specified at https://webassembly.github.io/spec/js-api/#defaultvalue

	Lars T Hansen [:lth] Assignee
	Comment 2 • 6 years ago

WasmGlobalObject::construct() does not treat an undefined 2nd argument the way it treats a missing 2nd argument.

	:Ms2ger (he/him; ⌚ UTC+1/+2) Reporter
	Comment 4 • 6 years ago

Comment on attachment 9009077 [details] [diff] [review]
bug1490286-ignore-undefined-value-for-global.patch

Review of attachment 9009077 [details] [diff] [review]:
-----------------------------------------------------------------

::: js/src/wasm/WasmJS.cpp
@@ +2463,2 @@
>      if (args.length() >= 2) {
>          RootedValue valueVal(cx, args.get(1));

args.get(1) will give you undefined on out-of-bounds access, so the length check is no longer necessary.

	Julian Seward [:jseward]
	Comment 5 • 6 years ago

Comment on attachment 9009077 [details] [diff] [review]
bug1490286-ignore-undefined-value-for-global.patch

Review of attachment 9009077 [details] [diff] [review]:
-----------------------------------------------------------------

Looks OK to me.  If you choose to remove the bounds check per comment 4,
maybe add a 1-liner comment which is essentially the last line of comment 4.

	Lars T Hansen [:lth] Assignee
	Comment 6 • 6 years ago

Changes our own test cases to conform as well.  Carrying jseward's r+.

	Pulsebot
	Comment 7 • 6 years ago

Pushed by lhansen@mozilla.com:
https://hg.mozilla.org/integration/mozilla-inbound/rev/ce36705acf73
Ignore 'undefined' value when constructing wasm global. r=jseward

	Cristian Brindusan [:cbrindusan]
	Comment 8 • 6 years ago
bugherder

https://hg.mozilla.org/mozilla-central/rev/ce36705acf73

	Chris Mills [:cmills]
	Comment 9 • 6 years ago

I've documented this by adding a description of the default value to:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WebAssembly/Global#Constructor_Syntax

I've also added a note about it to the Fx 64 rel notes:
https://developer.mozilla.org/en-US/docs/Mozilla/Firefox/Releases/64#JavaScript