1683217 - Crash in [@ webrender::screen_capture::AsyncScreenshotGrabber::get_screenshot] while profiling

Status: RESOLVED FIXED

(Core :: Graphics: WebRender, defect)

Description

[Andrew McCreight [:mccr8]]

Crash report: https://crash-stats.mozilla.org/report/index/89088588-70fa-4ef8-9534-a24f10201216

MOZ_CRASH Reason: called `Option::unwrap()` on a `None` value

Top 10 frames of crashing thread:

0 libxul.so RustMozCrash mozglue/static/rust/wrappers.cpp:17
1 libxul.so mozglue_static::panic_hook mozglue/static/rust/lib.rs:89
2 libxul.so core::ops::function::Fn::call /builds/worker/fetches/rustc/lib/rustlib/src/rust/library/core/src/ops/function.rs:70
3 libxul.so std::panicking::rust_panic_with_hook library/std/src/panicking.rs:581
4 libxul.so std::panicking::begin_panic_handler::{{closure}} library/std/src/panicking.rs:484
5 libxul.so std::sys_common::backtrace::__rust_end_short_backtrace library/std/src/sys_common/backtrace.rs:153
6 libxul.so rust_begin_unwind library/std/src/panicking.rs:483
7 libxul.so core::panicking::panic_fmt library/core/src/panicking.rs:85
8 libxul.so core::panicking::panic library/core/src/panicking.rs:50
9 libxul.so webrender::screen_capture::AsyncScreenshotGrabber::get_screenshot gfx/wr/webrender/src/screen_capture.rs:121

user comments: " when trying to catch a performance profiles while webrender is on and scale is 125%" and "while profiling on firefox"

Comment 1

[Jamie Nicol [:jnicol]]

Crash while profiling reported in bug 1682135.

Comment 2

[Markus Stange [:mstange]]

Better stack:

core::option::Option<T>::unwrap
/builds/worker/fetches/rustc/lib/rustlib/src/rust/library/core/src/option.rs:383
euclid::size::Size2D<T,U>::cast
/builds/worker/checkouts/gecko/third_party/rust/euclid/src/size.rs:285
euclid::size::Size2D<T,U>::to_i32
/builds/worker/checkouts/gecko/third_party/rust/euclid/src/size.rs:351
webrender::screen_capture::AsyncScreenshotGrabber::get_screenshot
/builds/worker/checkouts/gecko/gfx/wr/webrender/src/screen_capture.rs:121

So (window_rect.size.to_f32() * scale).round() is not an integer.
Maybe there is divide by zero in the computation of scale? If window_rect were zero-sized, this could happen.

Barret, could you take a look?

Comment 3

[Beth Rennie [:beth] (she/her)]

yeah it looks like we're dividing by zero here, ending up with infinity, and not being able to stuff that into an i32. We should probably bail before way before here if we are going to be recording a 0-sized window and maybe assert here that scale is not infinite.

Comment 4

[Beth Rennie [:beth] (she/her)]

Attachment: Bug 1683217 - Require non-zero window size for profiler screenshots in WebRender r?mstange

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/3c4f4a60fa40
Require non-zero window size for profiler screenshots in WebRender r=mstange

Comment 6

[Sebastian Hengst [:aryx] (needinfo me if it's about an intermittent or backout)]

https://hg.mozilla.org/mozilla-central/rev/3c4f4a60fa40