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tst_QGraphicsItem: check that qgraphicsitem_cast casts correctly

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GCC, with ubsan and optimization enabled, issues -Warray-bounds for
the cast from &polygonItem to QGraphicsTextItem*, because the latter
is-a QObject and the former is not, so the cast has to adjust the
pointer value to correct for the fact that QGraphicsItem is not the
first base class of QGraphicsTextItem:

  qgraphicsitem.h:973:56: warning: array subscript -1 is outside array bounds of ‘QGraphicsPolygonItem [1]’ [-Warray-bounds]
    973 |         || (item && int(Item::Type) == item->type()) ? static_cast<T>(item) : nullptr;
        |                                                        ^~~~~~~~~~~~~~~~~~~~
  tst_qgraphicsitem.cpp:3193:26: note: while referencing ‘polygonItem’

Check the implementation is correct in this respect by not just
checking for nullptr or non-nullptr, but checking that the result
matches what dynamic_cast produces.

We can assume dynamic_cast works on QGraphicsItems because QPA is
using dynamic_cast, so both QtGui and QtWidgets need to have been
compiled with RTTI enabled.

This doesn't eliminate the GCC warning, but confirms that it is a
False Positive.

Pick-to: 6.8 6.5
Change-Id: Ifc262cb6e715e8e68c180855adc2467960da89a1
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
(cherry picked from commit 101427957b59b715d0865cbdba12590fe11d1d10)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
This commit is contained in:
Marc Mutz 2025-03-25 13:53:00 +01:00 committed by Qt Cherry-pick Bot
parent a50425de58
commit c5beecbcc0
1 changed files with 64 additions and 32 deletions
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96
tests/auto/widgets/graphicsview/qgraphicsitem/tst_qgraphicsitem.cpp
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@ -3191,46 +3191,78 @@ void tst_QGraphicsItem::graphicsitem_cast()
QGraphicsTextItem textItem;
const QGraphicsTextItem *pTextItem = &textItem;
QVERIFY(qgraphicsitem_cast<QGraphicsPathItem *>(&pathItem));
//QVERIFY(qgraphicsitem_cast<QAbstractGraphicsPathItem *>(&pathItem));
QVERIFY(qgraphicsitem_cast<QGraphicsItem *>(&pathItem));
QVERIFY(qgraphicsitem_cast<const QGraphicsItem *>(pPathItem));
QVERIFY(qgraphicsitem_cast<const QGraphicsPathItem *>(pPathItem));
QCOMPARE_EQ(qgraphicsitem_cast<QGraphicsPathItem *>(&pathItem),
dynamic_cast<QGraphicsPathItem *>(&pathItem));
//QCOMPARE_EQ(qgraphicsitem_cast<QAbstractGraphicsPathItem *>(&pathItem),
// dynamic_cast<QAbstractGraphicsPathItem *>(&pathItem));
QCOMPARE_EQ(qgraphicsitem_cast<QGraphicsItem *>(&pathItem),
dynamic_cast<QGraphicsItem *>(&pathItem));
QCOMPARE_EQ(qgraphicsitem_cast<const QGraphicsItem *>(pPathItem),
dynamic_cast<const QGraphicsItem *>(pPathItem));
QCOMPARE_EQ(qgraphicsitem_cast<const QGraphicsPathItem *>(pPathItem),
dynamic_cast<const QGraphicsPathItem *>(pPathItem));
QVERIFY(qgraphicsitem_cast<QGraphicsRectItem *>(&rectItem));
QVERIFY(qgraphicsitem_cast<QGraphicsItem *>(&rectItem));
QVERIFY(qgraphicsitem_cast<const QGraphicsItem *>(pRectItem));
QVERIFY(qgraphicsitem_cast<const QGraphicsRectItem *>(pRectItem));
QCOMPARE_EQ(qgraphicsitem_cast<QGraphicsRectItem *>(&rectItem),
dynamic_cast<QGraphicsRectItem *>(&rectItem));
QCOMPARE_EQ(qgraphicsitem_cast<QGraphicsItem *>(&rectItem),
dynamic_cast<QGraphicsItem *>(&rectItem));
QCOMPARE_EQ(qgraphicsitem_cast<const QGraphicsItem *>(pRectItem),
dynamic_cast<const QGraphicsItem *>(pRectItem));
QCOMPARE_EQ(qgraphicsitem_cast<const QGraphicsRectItem *>(pRectItem),
dynamic_cast<const QGraphicsRectItem *>(pRectItem));
QVERIFY(qgraphicsitem_cast<QGraphicsEllipseItem *>(&ellipseItem));
QVERIFY(qgraphicsitem_cast<QGraphicsItem *>(&ellipseItem));
QVERIFY(qgraphicsitem_cast<const QGraphicsItem *>(pEllipseItem));
QVERIFY(qgraphicsitem_cast<const QGraphicsEllipseItem *>(pEllipseItem));
QCOMPARE_EQ(qgraphicsitem_cast<QGraphicsEllipseItem *>(&ellipseItem),
dynamic_cast<QGraphicsEllipseItem *>(&ellipseItem));
QCOMPARE_EQ(qgraphicsitem_cast<QGraphicsItem *>(&ellipseItem),
dynamic_cast<QGraphicsItem *>(&ellipseItem));
QCOMPARE_EQ(qgraphicsitem_cast<const QGraphicsItem *>(pEllipseItem),
dynamic_cast<const QGraphicsItem *>(pEllipseItem));
QCOMPARE_EQ(qgraphicsitem_cast<const QGraphicsEllipseItem *>(pEllipseItem),
dynamic_cast<const QGraphicsEllipseItem *>(pEllipseItem));
QVERIFY(qgraphicsitem_cast<QGraphicsPolygonItem *>(&polygonItem));
//QVERIFY(qgraphicsitem_cast<QAbstractGraphicsPathItem *>(&polygonItem));
QVERIFY(qgraphicsitem_cast<QGraphicsItem *>(&polygonItem));
QVERIFY(qgraphicsitem_cast<const QGraphicsItem *>(pPolygonItem));
QVERIFY(qgraphicsitem_cast<const QGraphicsPolygonItem *>(pPolygonItem));
QCOMPARE_EQ(qgraphicsitem_cast<QGraphicsPolygonItem *>(&polygonItem),
dynamic_cast<QGraphicsPolygonItem *>(&polygonItem));
//QCOMPARE_EQ(qgraphicsitem_cast<QAbstractGraphicsPathItem *>(&polygonItem),
// dynamic_cast<QAbstractGraphicsPathItem *>(&polygonItem));
QCOMPARE_EQ(qgraphicsitem_cast<QGraphicsItem *>(&polygonItem),
dynamic_cast<QGraphicsItem *>(&polygonItem));
QCOMPARE_EQ(qgraphicsitem_cast<const QGraphicsItem *>(pPolygonItem),
dynamic_cast<const QGraphicsItem *>(pPolygonItem));
QCOMPARE_EQ(qgraphicsitem_cast<const QGraphicsPolygonItem *>(pPolygonItem),
dynamic_cast<const QGraphicsPolygonItem *>(pPolygonItem));
QVERIFY(qgraphicsitem_cast<QGraphicsLineItem *>(&lineItem));
QVERIFY(qgraphicsitem_cast<QGraphicsItem *>(&lineItem));
QVERIFY(qgraphicsitem_cast<const QGraphicsItem *>(pLineItem));
QVERIFY(qgraphicsitem_cast<const QGraphicsLineItem *>(pLineItem));
QCOMPARE_EQ(qgraphicsitem_cast<QGraphicsLineItem *>(&lineItem),
dynamic_cast<QGraphicsLineItem *>(&lineItem));
QCOMPARE_EQ(qgraphicsitem_cast<QGraphicsItem *>(&lineItem),
dynamic_cast<QGraphicsItem *>(&lineItem));
QCOMPARE_EQ(qgraphicsitem_cast<const QGraphicsItem *>(pLineItem),
dynamic_cast<const QGraphicsItem *>(pLineItem));
QCOMPARE_EQ(qgraphicsitem_cast<const QGraphicsLineItem *>(pLineItem),
dynamic_cast<const QGraphicsLineItem *>(pLineItem));
QVERIFY(qgraphicsitem_cast<QGraphicsPixmapItem *>(&pixmapItem));
QVERIFY(qgraphicsitem_cast<QGraphicsItem *>(&pixmapItem));
QVERIFY(qgraphicsitem_cast<const QGraphicsItem *>(pPixmapItem));
QVERIFY(qgraphicsitem_cast<const QGraphicsPixmapItem *>(pPixmapItem));
QCOMPARE_EQ(qgraphicsitem_cast<QGraphicsPixmapItem *>(&pixmapItem),
dynamic_cast<QGraphicsPixmapItem *>(&pixmapItem));
QCOMPARE_EQ(qgraphicsitem_cast<QGraphicsItem *>(&pixmapItem),
dynamic_cast<QGraphicsItem *>(&pixmapItem));
QCOMPARE_EQ(qgraphicsitem_cast<const QGraphicsItem *>(pPixmapItem),
dynamic_cast<const QGraphicsItem *>(pPixmapItem));
QCOMPARE_EQ(qgraphicsitem_cast<const QGraphicsPixmapItem *>(pPixmapItem),
dynamic_cast<const QGraphicsPixmapItem *>(pPixmapItem));
QVERIFY(qgraphicsitem_cast<QGraphicsTextItem *>(&textItem));
QVERIFY(qgraphicsitem_cast<QGraphicsItem *>(&textItem));
QVERIFY(qgraphicsitem_cast<const QGraphicsItem *>(pTextItem));
QVERIFY(qgraphicsitem_cast<const QGraphicsTextItem *>(pTextItem));
QCOMPARE_EQ(qgraphicsitem_cast<QGraphicsTextItem *>(&textItem),
dynamic_cast<QGraphicsTextItem *>(&textItem));
QCOMPARE_EQ(qgraphicsitem_cast<QGraphicsItem *>(&textItem),
dynamic_cast<QGraphicsItem *>(&textItem));
QCOMPARE_EQ(qgraphicsitem_cast<const QGraphicsItem *>(pTextItem),
dynamic_cast<const QGraphicsItem *>(pTextItem));
QCOMPARE_EQ(qgraphicsitem_cast<const QGraphicsTextItem *>(pTextItem),
dynamic_cast<const QGraphicsTextItem *>(pTextItem));
// and some casts that _should_ fail:
QVERIFY(!qgraphicsitem_cast<QGraphicsEllipseItem *>(&pathItem));
QVERIFY(!qgraphicsitem_cast<const QGraphicsTextItem *>(pPolygonItem));
QCOMPARE_EQ(qgraphicsitem_cast<QGraphicsEllipseItem *>(&pathItem),
dynamic_cast<QGraphicsEllipseItem *>(&pathItem));
QCOMPARE_EQ(qgraphicsitem_cast<const QGraphicsTextItem *>(pPolygonItem),
dynamic_cast<const QGraphicsTextItem *>(pPolygonItem));
// and this shouldn't crash
QGraphicsItem *ptr = nullptr;