GLContext: if creating a context fails, deleting it causes crash

[Gerry Boland]

See here:
http://paste.ubuntu.com/16343869/

this is the relevant code from qsgthreadedrendererloop.cpp:

        if (!w->thread->gl) {
            w->thread->gl = new QOpenGLContext();
            if (qt_gl_global_share_context())
                w->thread->gl->setShareContext(qt_gl_global_share_context());
            w->thread->gl->setFormat(w->window->requestedFormat());
            w->thread->gl->setScreen(w->window->screen());
            if (!w->thread->gl->create()) {
                const bool isEs = w->thread->gl->isOpenGLES();
                delete w->thread->gl;
                w->thread->gl = 0;
                handleContextCreationFailure(w->window, isEs);
                return;
            }

Qt is creating a GL context object, but creation fails. In cleaning up, QtUbuntu crashes as it's tries to release an invalid context.

[Albert Astals Cid (aacid)]

FWIW

(gdb) print mEglDisplay
$1 = (EGLDisplay) 0x9de8ad8
(gdb) print mEglContext
$2 = (EGLContext) 0x0

[Albert Astals Cid (aacid)]

Interestingly we have
    Q_ASSERT(mEglContext != EGL_NO_CONTEXT);
in the constructor of UbuntuOpenGLContext, and
    ./EGL/egl.h:98:#define EGL_NO_CONTEXT ((EGLContext)0)

but since it's a Q_ASSERT and not an ASSERT is not crashing there

[Gerry Boland (gerboland)]

True. We also shouldn't even try to call eglDestroyContext on a null context.

[Daniel van Vugt (vanvugt)]

I was thinking the same thing in bug 1549455. Shouldn't this just be a qtubuntu task under bug 1549455 instead?

[Gerry Boland (gerboland)]

@vanvugt I wish it were, this is a fairly simple "don'd delete something that wasn't created" issue. Bug 1549455 is a bigger problem, it seems qt is unable to choose a good egl config to render at. More details given there.

[Emanuele Antonio Faraone (emanueleant03)]

And now?

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.