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authorMarc Mutz <marc.mutz@kdab.com>2017-04-14 12:39:20 +0200
committerMarc Mutz <marc.mutz@kdab.com>2017-04-14 12:29:35 +0000
commit5662234afaf23d88e1f3fa4bee2a59b61bd0c267 (patch)
treeb97cef8b7cad66e37b9f3900c7ec216e73cc2a88 /src
parent98e0cb0a28845fd6b808c25d2e049f8da1f9867c (diff)
QMatrix4x4: fix aliasing problem in operator*=
When multiplying a QMatrix4x4 by itself, we were clobbering the very matrix we read from. Employ read-caching to avoid this aliasing problem. [ChangeLog][QtGui][QMatrix4x4] operator*=() now calculates the correct result even if the RHS and LHS are the same object. Change-Id: I8534d56cfdd62c336577125127f05173fcec2873 Reviewed-by: Sean Harmer <sean.harmer@kdab.com>
Diffstat (limited to 'src')
-rw-r--r--src/gui/math3d/qmatrix4x4.h3
1 files changed, 2 insertions, 1 deletions
diff --git a/src/gui/math3d/qmatrix4x4.h b/src/gui/math3d/qmatrix4x4.h
index aca685920e..4db96d07c0 100644
--- a/src/gui/math3d/qmatrix4x4.h
+++ b/src/gui/math3d/qmatrix4x4.h
@@ -423,8 +423,9 @@ inline QMatrix4x4& QMatrix4x4::operator-=(const QMatrix4x4& other)
return *this;
}
-inline QMatrix4x4& QMatrix4x4::operator*=(const QMatrix4x4& other)
+inline QMatrix4x4& QMatrix4x4::operator*=(const QMatrix4x4& o)
{
+ const QMatrix4x4 other = o; // prevent aliasing when &o == this ### Qt 6: take o by value
flagBits |= other.flagBits;
if (flagBits < Rotation2D) {