My app crashed inside Qt internal function

[jiandingzhe]

I want to make a QtQuick app that show some 3D model. However when I run the program, the main window will show for a blink, then it crashes instantly. The debugger shows it is inside Qt inner rendering function, so I have no idea of how to find it out.

The model is contained in a QSGGeometry:
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// Profile3DWidget is my subclass of QQuickItem
void Profile3DWidget::build_shape()
{
std::printf("begin Profile3DWidget::build_shape\n");
QSGGeometry::Attribute attrs[] = {
QSGGeometry::Attribute::create(0, 4, GL_FLOAT, true),
QSGGeometry::Attribute::create(1, 4, GL_FLOAT, false),
};

QSGGeometry::AttributeSet attr_set = {2, sizeof(float)*8, attrs};

std::printf("create geometry\n");
shape = new QSGGeometry(attr_set, 4, 4, GL_UNSIGNED_INT);
node->setGeometry(shape);
shape->setDrawingMode(GL_TRIANGLE_STRIP);

std::printf("set vertex data\n");
MyVertex* vertices = (MyVertex*)shape->vertexData();
vertices[0].set_position(-10, -10, 0, 1);
vertices[0].set_color(1, 0, 0, 1);
vertices[1].set_position(10, -10, 0, 1);
vertices[1].set_color(0, 1, 0, 1);
vertices[2].set_position(10, 10, 0, 1);
vertices[2].set_color(0, 0, 1, 1);
vertices[3].set_position(-10, 10, 0, 1);
vertices[3].set_color(0.5, 0.5, 0.5, 1);

std::printf("set index data\n");
uint* indices = shape->indexDataAsUInt();
indices[0] = 0;
indices[1] = 1;
indices[2] = 2;
indices[3] = 3;

std::printf("end Profile3DWidget::build_shape\n");

}
@

This is the implemented updatePaintNode function. The node is already created in Profile3DWidget constructor. We simply update its matrix, and return it.
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QSGNode* Profile3DWidget::updatePaintNode(QSGNode * old_node, UpdatePaintNodeData * data)
{
std::printf("begin Profile3DWidget::updatePaintNode\n");
if (!shape)
build_shape();

QSGTransformNode* transform_node = data->transformNode;

QMatrix4x4 mat = matrix_project;
mat *= matrix_camera;
mat *= matrix_object;
transform_node->setMatrix(mat);

std::printf("end Profile3DWidget::updatePaintNode: return %p\n", node);
return node;

}
@
And these are some key functions of the re-implemented shader class. The GLSL code is a simple vertex and color processor, so I don't post it here:
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char const* const* DataProfileShader::attributeNames() const
{
static const char* const names[] = {"vtx", "vtx_color", 0};
return names;
}

void DataProfileShader::updateState(const RenderState &state, QSGMaterial *newMaterial, QSGMaterial *oldMaterial)
{
Q_ASSERT(program()->isLinked());

if (state.isMatrixDirty())
{
    program()->setUniformValue(id_matrix, state.combinedMatrix());
}

}
void DataProfileShader::initialize()
{
QSGMaterialShader::initialize();
id_matrix = program()->uniformLocation("matrix");
}
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This is the crash back trace:
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0 ?? /home/yangxi/software/Qt/5.3/gcc_64/lib/libQt5Quick.so.5 0x7ffff79554d6
1 QSGBatchRenderer::Renderer::renderBatches() /home/yangxi/software/Qt/5.3/gcc_64/lib/libQt5Quick.so.5 0x7ffff79566bd
2 QSGBatchRenderer::Renderer::render() /home/yangxi/software/Qt/5.3/gcc_64/lib/libQt5Quick.so.5 0x7ffff795cfea
3 QSGRenderer::renderScene(QSGBindable const&) /home/yangxi/software/Qt/5.3/gcc_64/lib/libQt5Quick.so.5 0x7ffff796918e
4 QSGRenderer::renderScene() /home/yangxi/software/Qt/5.3/gcc_64/lib/libQt5Quick.so.5 0x7ffff7969587
5 QSGRenderContext::renderNextFrame(QSGRenderer*, unsigned int) /home/yangxi/software/Qt/5.3/gcc_64/lib/libQt5Quick.so.5 0x7ffff7976e48
6 QQuickWindowPrivate::renderSceneGraph(QSize const&) /home/yangxi/software/Qt/5.3/gcc_64/lib/libQt5Quick.so.5 0x7ffff79b5d78
7 ?? /home/yangxi/software/Qt/5.3/gcc_64/lib/libQt5Quick.so.5 0x7ffff7993326
8 ?? /home/yangxi/software/Qt/5.3/gcc_64/lib/libQt5Quick.so.5 0x7ffff7993e9e
9 QWindow::event(QEvent*) /home/yangxi/software/Qt/5.3/gcc_64/lib/libQt5Gui.so.5 0x7ffff6034909
10 QQuickWindow::event(QEvent*) /home/yangxi/software/Qt/5.3/gcc_64/lib/libQt5Quick.so.5 0x7ffff79c00cb
11 QApplicationPrivate::notify_helper(QObject*, QEvent*) /home/yangxi/software/Qt/5.3/gcc_64/lib/libQt5Widgets.so.5 0x7ffff6b15724
12 QApplication::notify(QObject*, QEvent*) /home/yangxi/software/Qt/5.3/gcc_64/lib/libQt5Widgets.so.5 0x7ffff6b18d46
13 QCoreApplication::notifyInternal(QObject*, QEvent*) /home/yangxi/software/Qt/5.3/gcc_64/lib/libQt5Core.so.5 0x7ffff5ae0fc4
14 QGuiApplicationPrivate::processExposeEvent(QWindowSystemInterfacePrivate::ExposeEvent*) /home/yangxi/software/Qt/5.3/gcc_64/lib/libQt5Gui.so.5 0x7ffff6028587
15 QGuiApplicationPrivate::processWindowSystemEvent(QWindowSystemInterfacePrivate::WindowSystemEvent*) /home/yangxi/software/Qt/5.3/gcc_64/lib/libQt5Gui.so.5 0x7ffff602f665
16 QWindowSystemInterface::sendWindowSystemEvents(QFlagsQEventLoop::ProcessEventsFlag) /home/yangxi/software/Qt/5.3/gcc_64/lib/libQt5Gui.so.5 0x7ffff60145b8
17 ?? /home/yangxi/software/Qt/5.3/gcc_64/plugins/platforms/libqxcb.so 0x7fffeeeeca70
18 g_main_context_dispatch /lib/x86_64-linux-gnu/libglib-2.0.so.0 0x7ffff4277c5d
19 ?? /lib/x86_64-linux-gnu/libglib-2.0.so.0 0x7ffff4277f48
20 g_main_context_iteration /lib/x86_64-linux-gnu/libglib-2.0.so.0 0x7ffff4277ffc
...
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