CODEWITHSUNDEEP
regexqt
Arni Gudjonsson
Arni Gudjonsson

Reputation: 544

QT QRegularExpression QRegularExpressionMatchIterator not working (SIGSEGV)

I'm trying to use QRegularExpression and it's been working fine for all my patterns exept this.

I have this text:

TYPE "ASDF"
   some content
END_TYPE

TYPE "QWER"
   some other content
END_TYPE

TYPE "ZXCV"
   blablablabla
END_TYPE

and I want to match all TYPE...END_TYPE blocks (3 matches) in a QRegularExpression like this

QRegularExpression re("(TYPE(?:[^E]|E[^N]|EN[^D]|END[^_]|END_[^T])*END_TYPE)", QRegularExpression::DotMatchesEverythingOption);
QRegularExpressionMatchIterator i = re.globalMatch(text);
while (i.hasNext()) {
    QRegularExpressionMatch match = i.next();
    if (match.hasMatch()) {
        QString captured = match.captured(0);
        //.. and do some stuff with that string
    }
}

but when I build and debug the code I get a Segmentation fault error window at the QRegularExpressionMatchIterator:

The inferior stopped because it received a signal from the Operating System. Signal Name: SIGSEGV, Signal meaning: Segmentation fault

I've also tried using negative look-arounds: 

(TYPE ((?!END_TYPE))+END_TYPE)

This does not give me an error but also gives me no match.

Does any one have any idea what I'm doing wrong here or suggestion on how I can improve the regular expression? Any suggestions are greatly appreciated :)

Upvotes: 0

Views: 2050

Answers (1)

Arni Gudjonsson
Arni Gudjonsson

Reputation: 544

Ok with great help from RyanJ and CAustin I solved my problem. this is how the code looks now:

QRegularExpression re("(TYPE .+END_TYPE)");
re.setPatternOptions(QRegularExpression::DotMatchesEverythingOption | QRegularExpression::InvertedGreedinessOption);
QRegularExpressionMatchIterator i = re.globalMatch(text);
while (i.hasNext()) {
    QRegularExpressionMatch match = i.next();
    if (match.hasMatch()) {
        QString captured = match.captured(0);
    }
}

It looks like QRegularExpression does not support negative look-arounds like (TYPE ((?!END_TYPE))+END_TYPE) or grouping like (TYPE(?:[^E]|E[^N]|EN[^D]|END[^]|END[^T])*END_TYPE)

So the fix is to use the QRegularExpression::InvertedGreedinessOption (works the same as QRegExp::setMinimal()) for minimal matching.

Thank you RyanJ and CAustin for your help!

Upvotes: 2

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