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QMap: don't dereference nullptr

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root(), leftNode() and rightNode() can be nullptr.
These pieces of code happened to work because the first thing lowerBound()
does is

   Node *n = this;
   // ...
   while (n)
     // ...

But that is _after_ dereferencing nullptr, which is undefined behavior.

So, check first, then deref.

Change-Id: I9137bf6e21014cd68404a7e49a748910b1d768cf
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
This commit is contained in:
Marc Mutz 2013-09-15 18:51:36 +02:00 committed by The Qt Project
parent bc9c03a550
commit 250190b39b
1 changed files with 7 additions and 5 deletions
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12
src/corelib/tools/qmap.h
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@ -288,9 +288,11 @@ void QMapData<Key, T>::deleteNode(QMapNode<Key, T> *z)
template <class Key, class T>
QMapNode<Key, T> *QMapData<Key, T>::findNode(const Key &akey) const
{
Node *lb = root()->lowerBound(akey);
if (lb && !qMapLessThanKey(akey, lb->key))
return lb;
if (Node *r = root()) {
Node *lb = r->lowerBound(akey);
if (lb && !qMapLessThanKey(akey, lb->key))
return lb;
}
return 0;
}
@ -307,10 +309,10 @@ void QMapData<Key, T>::nodeRange(const Key &akey, QMapNode<Key, T> **firstNode,
} else if (qMapLessThanKey(n->key, akey)) {
n = n->rightNode();
} else {
*firstNode = n->leftNode()->lowerBound(akey);
*firstNode = n->leftNode() ? n->leftNode()->lowerBound(akey) : 0;
if (!*firstNode)
*firstNode = n;
*lastNode = n->rightNode()->upperBound(akey);
*lastNode = n->rightNode() ? n->rightNode()->upperBound(akey) : 0;
if (!*lastNode)
*lastNode = l;
return;