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QVariantAnimation: fix UB (FP 0/0) in interpolated() arg calculation

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When startProgress, endProgress, and progress were all 0 (as provoked
by tst_QPropertyAnimation::startWithoutStartValue()), we'd calculate
0/0 and ubsan complained:

  qvariantanimation.cpp:284:60: runtime error: division by zero

Fix by detecting progress - startProgress == 0 and setting
localProgress = 0.0 in that case. This is a logical result, even
though it might not be what IEEE754 rules would have yielded.

A more comprehensive change that aims to reliably keep localProgress
∈ [0,1] and thus avoid the infinities when endProgress ==
startProgress, is outside the scope of this patch, which deals only
with the UBSan error.

Pick-to: 6.3 6.2 5.15
Change-Id: I5258b054a2060006795f49fb1cd7604aea3ed46b
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
Reviewed-by: Jan Arve Sæther <jan-arve.saether@qt.io>
This commit is contained in:
Marc Mutz 2021-12-16 09:04:01 +01:00
parent b330016cf2
commit 52da10f645
1 changed files with 3 additions and 1 deletions
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4
src/corelib/animation/qvariantanimation.cpp
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@ -278,7 +278,9 @@ void QVariantAnimationPrivate::setCurrentValueForProgress(const qreal progress)
const qreal startProgress = currentInterval.start.first;
const qreal endProgress = currentInterval.end.first;
const qreal localProgress = (progress - startProgress) / (endProgress - startProgress);
const qreal localProgress =
qIsNull(progress - startProgress) ? 0.0 // avoid 0/0 below
/* else */ : (progress - startProgress) / (endProgress - startProgress);
QVariant ret = q->interpolated(currentInterval.start.second,
currentInterval.end.second,