CODEWITHSUNDEEP
c++qttaglib
shadowCODE
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Reputation: 213

can't read tag with TagLib

Downloaded taglib 1.9 from https://taglib.github.io/ and compiled with the instructions provided in the INSTALL file.

The code below crashes with error "The program has unexpectedly finished."

#include "mainwindow.h"
#include <QApplication>
#include <QDebug>

#include <taglib/mp4file.h> 
#include <taglib/mpegfile.h>
#include <taglib/fileref.h>
#include <taglib/taglib.h>
#include <taglib/tag.h>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    TagLib::FileName fn(QString("C:/Users/Bill/Desktop/02 Am I Wrong.mp3").toStdString().c_str());
    TagLib::FileRef ref(fn);

    qDebug() << QString::fromStdString(std::string(ref.tag()->artist().toCString()));
    return a.exec();
}

Running in debug mode show me null dereference fileref.cpp at 

bool FileRef::isNull() const
{
  return !d->file || !d->file->isValid();
}

Running Windows 10 insider preview with static built Qt 5.0.2

I've toiled and toiled and found no helpful result.

Upvotes: 0

Views: 1206

Answers (1)

Timo
Timo

Reputation: 1814

The Pointer returned by QString.toStdString()..c_str() is only valid while the QString object is still alive. In your case that's only on the line where you're creating it.
So either keep a reference to your QString or don't use QString at all.

TagLib::FileRef ref("C:/Users/Bill/Desktop/02 Am I Wrong.mp3");
qDebug() << ref.tag()->artist().toCString();

Furthermore you should add some error checks. Here's an example without using qt:

#include <taglib/fileref.h>
#include <taglib/taglib.h>
#include <taglib/tag.h>

int main(int argc, char *argv[])
{
    TagLib::FileRef ref("./Falco Benz - Hat Tricks (Original Mix).mp3");
    if(!ref.isNull() && ref.tag() != NULL) {
        std::cout << ref.tag()->artist().toCString() << std::endl;
    }
}

If I omit the error checks, and the file does not exists, I get a segfault.

Upvotes: 1

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