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QVectorND: make some constructors explicit

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QVector2D has implicit conversions towards QVector3D/4D, and
QVector3D has an implicit conversion towards QVector4D. Although
in principle this is fine because it's not a data loss, it's still
sketchy; for instance, it allows mixed operations to compile:

  vector2d + vector3d;
  vector4d - vector3d;
  vector3d * vector4d; // !

(Random observation: the conversion from QPoint(F) to QVectorND are
actually already marked as explicit.)

This is a leftover not done for Qt 6.0. I am not making these opt-out:
having an implicit conversion here is outright *dangerous*, and any usage
that fails to compile needs to be inspected to make sure it was the
intended behavior.

[ChangeLog][Potentially Source-Incompatible Changes] The
QVector2D/3D/4D converting constructors from another QVectorND
now explicit. This was done to prevent a category of bugs resulting
from operations accidentally mixing QVectorND objects.

Fixes: QTBUG-90327
Change-Id: Ifcd873f6a0d3fc10b9e68c935fe1f69f86a2340b
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
This commit is contained in:
Giuseppe D'Angelo 2020-12-28 02:06:41 +01:00 committed by Volker Hilsheimer
parent f1465c621c
commit 5a0e5521e4
1 changed files with 3 additions and 3 deletions
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6
src/gui/math3d/qvectornd.h
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@ -196,7 +196,7 @@ public:
constexpr explicit QVector3D(QPoint point) noexcept;
constexpr explicit QVector3D(QPointF point) noexcept;
#ifndef QT_NO_VECTOR2D
constexpr QVector3D(QVector2D vector) noexcept;
constexpr explicit QVector3D(QVector2D vector) noexcept;
constexpr QVector3D(QVector2D vector, float zpos) noexcept;
#endif
#ifndef QT_NO_VECTOR4D
@ -340,11 +340,11 @@ public:
constexpr explicit QVector4D(QPoint point) noexcept;
constexpr explicit QVector4D(QPointF point) noexcept;
#ifndef QT_NO_VECTOR2D
constexpr QVector4D(QVector2D vector) noexcept;
constexpr explicit QVector4D(QVector2D vector) noexcept;
constexpr QVector4D(QVector2D vector, float zpos, float wpos) noexcept;
#endif
#ifndef QT_NO_VECTOR3D
constexpr QVector4D(QVector3D vector) noexcept;
constexpr explicit QVector4D(QVector3D vector) noexcept;
constexpr QVector4D(QVector3D vector, float wpos) noexcept;
#endif