QMap::clear() crash

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QMap::clear() crash



I'm running Qt-4.8.6 on Linux i686



I have a


QMap<quint32, QTreeWidgetItem *> mymap;



and when I simply call


mymap.clear();



the program crashes with stacktrace


...
#7 <signal handler called>
#8 0x0806f50c in QBasicAtomicInt::deref (this=0x34) at /usr/local/Trolltech/Qt-4.8.6/include/QtCore/qatomic_i386.h:110
#9 0xa968c452 in QMap<unsigned int, QTreeWidgetItem*>::operator= (this=0xc53c51c, other=@0xbfa04b28)
at /usr/local/Trolltech/Qt-4.8.6/include/QtCore/qmap.h:412
#10 0xa968c4d1 in QMap<unsigned int, QTreeWidgetItem*>::clear (this=0xc53c51c)
at /usr/local/Trolltech/Qt-4.8.6/include/QtCore/qmap.h:424
...



Sorry I can't paste full stacktrace/code cuz I don't own the code.



This problem doesn't happen every time, or I should say it happens very rarely, but it did happen. I googled but only found things like "reinstall Qt", "use same compiler", etc.



Is there anything else I can do?



EDIT



I can paste some related Qt source code if that helps


// qmap.h
template <class Key, class T>
Q_INLINE_TEMPLATE void QMap<Key, T>::clear()

*this = QMap<Key, T>();


template <class Key, class T>
Q_INLINE_TEMPLATE QMap<Key, T> &QMap<Key, T>::operator=(const QMap<Key, T> &other)

if (d != other.d)
QMapData* o = other.d;
o->ref.ref();
if (!d->ref.deref())
freeData(d);
d = o;
if (!d->sharable)
detach_helper();

return *this;


// qatomic_i386.h
inline bool QBasicAtomicInt::deref()

unsigned char ret;
asm volatile("lockn"
"decl %0n"
"setne %1"
: "=m" (_q_value), "=qm" (ret)
: "m" (_q_value)
: "memory");
return ret != 0;





Without an MCVE there is not much we can do to help. Use a debugger and check where the code crashes exactly.
– Sebastian
Aug 10 at 8:58





If it doesn't happen every time, you have something undefined in your code. The this=0x34 suggests that there is a null pointer somewhere. That there is any kind of problem with clear suggests that the map itself has become corrupted somehow.
– molbdnilo
Aug 10 at 9:02


this=0x34


clear





The two lines posted do not crash so in actual code the map itself is either already destroyed or corrupted by something.
– Öö Tiib
Aug 10 at 9:08





@molbdnilo You're right, thanks for correcting me.
– lubgr
Aug 10 at 9:10









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