1204165 - Assertion failure: this->is<T>(), at jsobj.h

Status: RESOLVED FIXED

(Core :: JavaScript Engine: JIT, defect)

Description

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

var x;
function f() {
    x = [];
    for (var i = 0; i < 1; ++i) {
        x.push("");
    }
    [0].concat(x);
}
f();
f();

asserts js debug shell on m-c changeset 7671701d15ca with --fuzzing-safe --no-threads --ion-eager --unboxed-arrays at Assertion failure: this->is<T>(), at jsobj.h

Configure options:

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-darwin12.5.0 --enable-debug --enable-nspr-build --enable-more-deterministic --with-ccache --enable-gczeal --enable-debug-symbols --disable-tests

python -u ~/funfuzz/js/compileShell.py -b "--enable-debug --enable-more-deterministic --enable-nspr-build" -r 7671701d15ca

autoBisect shows this is probably related to the following changeset:

The first bad revision is:
changeset:   https://hg.mozilla.org/mozilla-central/rev/e671afb66591
user:        Brian Hackett
date:        Fri Aug 21 11:49:50 2015 -0600
summary:     Bug 1176451 - Optimize Array.concat when used on different types of boxed vs. unboxed arrays, r=jandem.

Brian, is bug 1176451 a likely regressor?

Thanks Jesse for helping me reduce this.

Comment 1

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

Attachment: stack

(lldb) bt 5
* thread #1: tid = 0x46ce50, 0x0000000100096b38 js-dbg-64-dm-nsprBuild-darwin-7671701d15ca`js::DenseElementResult ArrayConcatDenseKernel<(JSValueType)4, (JSValueType)5>(JSContext*, JSObject*, JSObject*, JSObject*) + 52 at jsobj.h:547, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0x0)
  * frame #0: 0x0000000100096b38 js-dbg-64-dm-nsprBuild-darwin-7671701d15ca`js::DenseElementResult ArrayConcatDenseKernel<(JSValueType)4, (JSValueType)5>(JSContext*, JSObject*, JSObject*, JSObject*) + 52 at jsobj.h:547
    frame #1: 0x0000000100096b04 js-dbg-64-dm-nsprBuild-darwin-7671701d15ca`js::DenseElementResult ArrayConcatDenseKernel<(JSValueType)4, (JSValueType)5>(JSContext*, JSObject*, JSObject*, JSObject*) at UnboxedObject-inl.h:375
    frame #2: 0x0000000100096b04 js-dbg-64-dm-nsprBuild-darwin-7671701d15ca`js::DenseElementResult ArrayConcatDenseKernel<(JSValueType)4, (JSValueType)5>(cx=0x000000010075cae1, obj1=<unavailable>, obj2=<unavailable>, result=<unavailable>) + 708 at jsarray.cpp:2540
    frame #3: 0x000000010007efad js-dbg-64-dm-nsprBuild-darwin-7671701d15ca`js::array_concat_dense(cx=<unavailable>, obj1=<unavailable>, obj2=<unavailable>, result=<unavailable>) + 77 at jsarray.cpp:2570
    frame #4: 0x0000000100758ce4 js-dbg-64-dm-nsprBuild-darwin-7671701d15ca`js::jit::ArrayConcatDense(cx=0x000000010284c400, obj1=<unavailable>, obj2=<unavailable>, objRes=<unavailable>) + 52 at VMFunctions.cpp:357
(lldb)

Comment 2

[Fuzzing Team]

JSBugMon: Cannot process bug: Unable to automatically reproduce, please track manually.

Comment 3

[Brian Hackett [Laid off!]]

Attachment: patch

:(

Comment 4

[Pulsebot]

https://hg.mozilla.org/integration/mozilla-inbound/rev/ba7ce37de12e

Comment 5

[Wes Kocher (:KWierso) (Not reading bugmail; email directly if needed)]

https://hg.mozilla.org/mozilla-central/rev/ba7ce37de12e