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Never assume anything

because when you do, reality will teach you better
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m-kuhn committed Mar 2, 2019
1 parent dcc92de commit 82ca2dd8731163b5d50f9344baae5d6bf19267a9
Showing with 9 additions and 1 deletion.
  1. +9 −1 src/analysis/vector/geometry_checker/qgsfeaturepool.cpp
@@ -38,7 +38,15 @@ QgsFeaturePool::QgsFeaturePool( QgsVectorLayer *layer )

bool QgsFeaturePool::getFeature( QgsFeatureId id, QgsFeature &feature, QgsFeedback *feedback )
{
QgsReadWriteLocker locker( mCacheLock, QgsReadWriteLocker::Read );
// Why is there a write lock acquired here? Weird, we only want to read a feature from the cache, right?
// A method like `QCache::object(const Key &key) const` certainly would not modify its internals.
// Mmmh. What if reality was different?
// If one reads the docs very, very carefully one will find the term "reentrant" in the
// small print of the QCache docs. This is the hint that reality is different.
//
// https://bugreports.qt.io/browse/QTBUG-19794

QgsReadWriteLocker locker( mCacheLock, QgsReadWriteLocker::Write );
QgsFeature *cachedFeature = mFeatureCache.object( id );
if ( cachedFeature )
{

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