1300193 - Assertion failure: getDenseCapacity() == 0, at js/src/vm/NativeObject-inl.h:164

Status: RESOLVED FIXED

Description

[Gary Kwong [:gkw] [:nth10sd]]

The following testcase crashes on mozilla-central revision d5f20820c805 (build with --enable-debug --enable-more-deterministic, run with --fuzzing-safe --no-threads --no-baseline --no-ion):

x = [0];
x.length = 9;
Object.freeze(x);
x.reverse();


Backtrace:

0   js-dbg-64-dm-clang-darwin-d5f20820c805	0x000000010d74df63 js::NativeObject::extendDenseElements(js::ExclusiveContext*, unsigned int, unsigned int) + 531 (NativeObject-inl.h:164)
1   js-dbg-64-dm-clang-darwin-d5f20820c805	0x000000010d74d79b js::NativeObject::ensureDenseElements(js::ExclusiveContext*, unsigned int, unsigned int) + 587 (NativeObject-inl.h:229)
2   js-dbg-64-dm-clang-darwin-d5f20820c805	0x000000010cda7936 js::DenseElementResult ArrayReverseDenseKernel<(JSValueType)4>(JSContext*, JS::Handle<JSObject*>, unsigned int) + 86 (jsarray.cpp:1366)
3   js-dbg-64-dm-clang-darwin-d5f20820c805	0x000000010cd880fb js::array_reverse(JSContext*, unsigned int, JS::Value*) + 363 (jsarray.cpp:1420)
4   js-dbg-64-dm-clang-darwin-d5f20820c805	0x000000010d5a90cc js::InternalCallOrConstruct(JSContext*, JS::CallArgs const&, js::MaybeConstruct) + 716 (jscntxtinlines.h:236)
/snip

For detailed crash information, see attachment.

Comment 1

[Gary Kwong [:gkw] [:nth10sd]]

Created attachment 8787760 [details]
Detailed Crash Information

Comment 2

[Gary Kwong [:gkw] [:nth10sd]]

autoBisect shows this is probably related to the following changeset:

The first bad revision is:
changeset:   https://hg.mozilla.org/mozilla-central/rev/f95b25ae990d
user:        Leo Gaspard
date:        Mon Aug 29 15:00:35 2016 -0700
summary:     Bug 1283334 - Part 1: Do not sparsify dense arrays when freezing - Interpreter. r=jandem

Leo, is bug 1283334 a likely regressor?

Comment 3

[Leo Gaspard [:ekleog]]

It is, the assertion is too strict here as we no longer enforce frozen objects to be sparse, and I didn't notice it writing bug 1283334.

Comment 4

[Leo Gaspard [:ekleog]]

Created attachment 8787793 [details] [diff] [review]
freezing-dense-reverse.patch

Here is a patch that should fix the crash. The assertion relied on the enclosing `if` to assert that elements must be sparse. This patch makes accept frozen objects that have dense elements, as it was the point of bug 1283334.

Comment 5

[Leo Gaspard [:ekleog]]

Try run is available at https://treeherder.mozilla.org/#/jobs?repo=try&revision=ddc13ba3ae31

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/ba853a36a973
Make existing assertion that no longer holds more flexible. r=jandem

Comment 7

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/ba853a36a973