QMap iteration crash

[nullstellensatz]

I am using Qt 5.5 on Windows 8.1. When I run the code below, the application is able to get through one iteration, but crashes on the second one. 100% reproducible. (Copy/paste it into a Qt Creator instance and test; it might work for you).

#include <QCoreApplication>
#include <QDebug>
#include <utility>

using std::pair;

int main(int argc, char *argv[]) {
    QCoreApplication a(argc, argv);
    QMap<QString, pair<QString, QString> > table_def = {
        {"alpha", {"INTEGER", "PRIMARY KEY"}},
        {"beta", {"VARCHAR", ""}},
        {"gamma", {"VARCHAR", ""}},
        {"delta", {"REAL", "DEFAULT 0"}},
        {"epsilon", {"INTEGER", ""}},
        {"zeta", {"INTEGER", ""}},
        {"eta", {"INTEGER", ""}},
        {"theta", {"INTEGER", ""}},
        {"iota", {"VARCHAR", ""}},
        {"kappa", {"INTEGER", "DEFAULT 0"}},
        {"lambda", {"INTEGER", "DEFAULT 0"}}
    };

    QMapIterator<QString, pair<QString, QString> > it(table_def);
    while (it.hasNext()) {
      it.next();
      const QString& col_name = it.key();
      qDebug() << col_name;
      const QString& col_type = it.value().first;
      qDebug() << col_type;
      const QString& extra_def = it.value().second;
      qDebug() << extra_def;
    }
    return a.exec();
}

My Visual Studio debugger says: Unhandled exception at 0x000000006904E394 (Qt5Cored.dll) in helloqt.exe: 0xC0000005: Access violation reading location 0xFFFFFFFFFFFFFFFF.

If it is of any relevance, I added DEFINES += Q_COMPILER_INITIALIZER_LISTS in my project file to enable initialization of QContainers with initializer lists. Also, if I replace the STL pair with QPair, the application crashes at the first iteration.

I don't see anything wrong with this code. What could be happening?

[mrjj]

@nullstellensatz said:

qt 5.4.1 on win 7.
No crash with your code.
also added DEFINES += Q_COMPILER_INITIALIZER_LISTS

for test, if you change all "" (empty) to something , does it still crash ?
Just a thought since you say it crash on second. (first "")

Code looks perfectly valid to me.

[nullstellensatz]

The first entry to be printed is actually "theta" (since the entries are not ordered by key), which has an empty string as the second value.

[Chris Kawa]

Which version and update of VS are you using?
Initializer lists were infested with subtle but horrid bugs prior to VS2013 Update 3 and are not entirely standards conforming even in Update 4, although the above seems to compile and run fine with Qt5.5 in VS2013 Update 4 (the extra define seems not needed anymore?).

[nullstellensatz]

@Chris-Kawa The last time I updated Visual Studio was sometime in 2014. After getting the most recent version of Visual Studio this probelm went away.

[Chris Kawa]

Great.

Btw. you can check which update you're running by going to Help->About Microsoft Visual Studio.
For example the latest update reads
Microsoft Visual Studio 2013
Version 12.0.31101.00 Update 4

Btw 2. On monday (20.07.2015) VS 2015 comes out, which has greatly improved c++11 standard support.