1420382 - WGL context creation doesn't free the dummy context

Status: RESOLVED DUPLICATE of bug 1347731

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

Description

[Shimmer Huang]

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:57.0) Gecko/20100101 Firefox/57.0
Build ID: 20171112125346

Steps to reproduce:

The bug is located in source code @reateWindowOffscreenContext() in gfx\gl\GLContextProviderWGL.cpp, looks like a typo .

When the mozillar firefox creates WGL context via CreateWindowOffscreenContext(), it will call into OpenGL driver to create OpenGl context twice, and assign the context handler returned by OpenGL driver to a same variable twice, which means the 1st one would become a *zombie* context which will never be used/deleted. After tens of contexts have been created, OpenGL driver will fail to create new context due to out-of-memory.


Actual results:

In gfx\gl\GLContextProviderWGL.cpp

static already_AddRefed<GLContextWGL>
CreateWindowOffscreenContext()
{
    ....

    HGLRC context = sWGLLib.mSymbols.fCreateContext(dc);                      ------------>1st time to call wglCreateContext to create context
    if (sWGLLib.HasRobustness()) {
        int attribs[] = {
            LOCAL_WGL_CONTEXT_FLAGS_ARB, LOCAL_WGL_CONTEXT_ROBUST_ACCESS_BIT_ARB,
            LOCAL_WGL_CONTEXT_RESET_NOTIFICATION_STRATEGY_ARB, LOCAL_WGL_LOSE_CONTEXT_ON_RESET_ARB,
            0
        };

        context = sWGLLib.mSymbols.fCreateContextAttribsARB(dc, nullptr, attribs);
    } else {
        context = sWGLLib.mSymbols.fCreateContext(dc);    ------------>2nd time to call wglCreateContext to create context

    }

    if (!context) {
        return nullptr;
    }

    SurfaceCaps caps = SurfaceCaps::ForRGBA();
    RefPtr<GLContextWGL> glContext = new GLContextWGL(CreateContextFlags::NONE, caps,
                                                      true, dc, context, win);
    return glContext.forget();
}


Expected results:

We should not do the 1st call for wglCreateContext().

Comment 1

[Shimmer Huang]

More information, this issue would result some WebGL CTS cases fail in Win7.

Comment 2

[Aria Beingessner [:Gankra]]

(Don't know this code well) Jeff, does this look right to you? As easy to fix as it looks?

Comment 3

[Kelsey Gilbert [:jgilbert]]

We must have lost the delete somewhere.

Comment 4

[Pandurang Katkar]

Issue still observed with latest Firefox v.57.0.2