Wrong usage of QList::ConstIterator & QList::begin() ?

Thiago Macieira thiago at kde.org
Sat Oct 18 12:24:37 BST 2008

Albert Astals Cid wrote:
>A Dissabte 18 Octubre 2008, Christian Ehrlicher va escriure:
>> Hi,
>> While trying to fix some bugs in KFile* on windows I saw some places
>> like this:
>> for ( QStringList::ConstIterator it = m_dirList.begin();
>>        it != m_dirList.end() && !terminationRequested();
>>        ++it )
>> Imo the programmer here expects that m_dirList.detach() isn't called
>> but this is wrong.
>> m_dirList.begin() does a detach, returns a non-const iterator and then
>> the iterator is converted to a const iterator (see qlist.h:214 & 238).
>> Therefore I suggest to add QT_STRICT_ITERATORS to the kdelibs flags.
>> Or does this maybe break BC?
>This is not wrong, just not what the developer "really wanted" but it
> works just fine, albeit a bit slower.

In this case.

In some cases, mixing const and non-const iterators can lead to crashes, 
due to the container detaching in-between and pointers moving around.

QT_STRICT_ITERATORS is good for development, but not for release code.

  Thiago Macieira  -  thiago (AT) macieira.info - thiago (AT) kde.org
    PGP/GPG: 0x6EF45358; fingerprint:
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