1321437 - Differential Testing: Different output message involving Object.freeze

Status: RESOLVED FIXED

(Core :: JavaScript Engine: JIT, defect, P1)

Description

[Gary Kwong [:gkw] [:nth10sd] (NOT official MoCo now)]

(function() {
    "use strict";
    for (let z of [0, [1], 0]) {
        try {
            Object.freeze(z);
            for (var h in z) {};
            z[1] = 0;
        } catch (e) {
            print(e);
        }
    }
}());

$ ./js-dbg-64-dm-clang-darwin-8f1e42069983 --fuzzing-safe --no-threads --ion-eager testcase.js
TypeError: can't assign to properties of (new Number(0)): not an object
TypeError: 1 is read-only
TypeError: can't assign to properties of (new Number(0)): not an object

$ ./js-dbg-64-dm-clang-darwin-8f1e42069983 --fuzzing-safe --no-threads --baseline-eager --no-ion testcase.js
TypeError: can't assign to properties of (new Number(0)): not an object
TypeError: can't define array index property past the end of an array with non-writable length
TypeError: can't assign to properties of (new Number(0)): not an object
$


Tested this on m-c rev 8f1e42069983.

My configure flags are:

CC="clang -Qunused-arguments" CXX="clang++ -Qunused-arguments" AR=ar AUTOCONF=/usr/local/Cellar/autoconf213/2.13/bin/autoconf213 sh /Users/skywalker/trees/mozilla-central/js/src/configure --target=x86_64-apple-darwin14.5.0 --disable-jemalloc --enable-debug --enable-more-deterministic --with-ccache --enable-gczeal --enable-debug-symbols --disable-tests

python -u ~/funfuzz/js/compileShell.py -b "--enable-debug --enable-more-deterministic" -r 8f1e42069983

autoBisect shows this is probably related to the following changeset:

The first bad revision is:
changeset:   https://hg.mozilla.org/mozilla-central/rev/26e6632de510
user:        Leo Gaspard
date:        Thu Aug 25 16:28:31 2016 -0700
summary:     Bug 1283334 - Part 3: Do not sparsify dense arrays when freezing - Ion. r=nbp 

Jan, you last fixed bug 1314545 and bug 1317943 (which might be related), is bug 1283334 a likely regressor?

Comment 1

[Jan de Mooij [:jandem]]

Attachment: Patch

There are at least 3 different error messages we can throw for |frozenObject[x] = y| in strict mode. This patch changes ThrowReadOnlyError to call SetProperty to make sure we behave exactly the same as the interpreter. A bit lame but I can't think of a simpler fix.

Comment 2

[Gary Kwong [:gkw] [:nth10sd] (NOT official MoCo now)]

Jan, what might be next here?

Comment 3

[Jan de Mooij [:jandem]]

(In reply to Gary Kwong [:gkw] [:nth10sd] from comment #2)
> Jan, what might be next here?

I have to Try-server and land this, working on it...

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/7aef8faa6666
Fix ThrowReadOnlyError to match the error message we would throw in the VM. r=nbp

Comment 5

[Phil Ringnalda (:philor)]

https://hg.mozilla.org/mozilla-central/rev/7aef8faa6666