764254 - "ASSERTION: GetInputStream on invalid context?" after memory-pressure

Status: NEW

(Core :: Graphics: CanvasWebGL, defect, P3)

Description

[Jesse Ruderman]

Attachment: testcase

1. Install https://www.squarefree.com/extensions/domFuzzLite3.xpi
2. Load the testcase.

Result:

###!!! ASSERTION: GetInputStream on invalid context?: 'gl', file content/canvas/src/WebGLContext.cpp, line 607

Comment 1

[Jesse Ruderman]

Attachment: stack trace

Comment 2

[Benoit Jacob [:bjacob] (mostly away)]

This assertion, and the check below returning NS_ERROR_FAILURE if gl is null, seem bogus to me:

    NS_ASSERTION(gl, "GetInputStream on invalid context?");
    if (!gl)
        return NS_ERROR_FAILURE;

Indeed, if we just proceed, we're not going to dereference this gl pointer here, all what will happen is we'll call Render() which will immediately return without doing anything, so we'll be left with a gfxImageSurface in default state which is cleared (this constructor takes a aClear optional parameter that defaults to true). So the resulting image will be blank transparent black which seems like a very reasonable choice for a lost context. I don't see anywhere in the spec where we say what should be done in this case?

Comment 3

[Benoit Jacob [:bjacob] (mostly away)]

Attachment: remove apparently bad assert in GetInputStream