QT4.2 corrupted double-linked list and QRadioButton existance

[mtrpoland]

Hi again,
I have encountered an odd obstacle.
I implement MVC pattern using subclassed QTreeView as myView and QAbstractItemModel as myModel. I place the myView object in MyMVC that contains combo box and line edit, which are used as filter input. Anyway, everything works perfect with the whole application.

But when I add a few (commented below in mymvc.cpp) lines I get Core Dumped and the main window of my program just shows for a while and dissapears.

Above the backtrace I receive:
*** glibc detected *** ./PL09: corrupted double-linked list: 0x08124aa8 ***
(PL09 is a name of a application file)

Here is the code of mymvc.h

#ifndef MTR_SAFETY_DECLARATION_FOR_MYMVC_H
#define MTR_SAFETY_DECLARATION_FOR_MYMVC_H
#include <QWidget>
namespace MTR {
class Book;
class SBook;
}
class myView;
class myModel;
class QGridLayout;
class QLabel;
class QComboBox;
class QLineEdit;
class QRadioButton;
 
class MyMVC : public QWidget {
	Q_OBJECT
public:
	MyMVC(QList<MTR::Book>* list = 0, QWidget* parent = 0);
	void prodModel(QList<MTR::Book>*);
public slots:
	bool getCaseSensitive(void) { return caseSensitive; }
	void setCaseSensitive(bool cs) { caseSensitive = cs; }
signals:
	void doubleClickInTreeView(int);
private:
	QList<MTR::SBook>* slist;
	QLineEdit* le;
	QComboBox* qcb;
	myModel* model;
	myView* qtv;
	QGridLayout* qvb;
	QLabel* label;
	bool caseSensitive;
        QRadioButton* radioOne;
	QRadioButton* radioTwo;
};
 
#endif

#ifndef MTR_SAFETY_DECLARATION_FOR_MYMVC_H
#define MTR_SAFETY_DECLARATION_FOR_MYMVC_H
#include <QWidget>
namespace MTR {
class Book;
class SBook;
}
class myView;
class myModel;
class QGridLayout;
class QLabel;
class QComboBox;
class QLineEdit;
class QRadioButton;

class MyMVC : public QWidget {
	Q_OBJECT
public:
	MyMVC(QList<MTR::Book>* list = 0, QWidget* parent = 0);
	void prodModel(QList<MTR::Book>*);
public slots:
	bool getCaseSensitive(void) { return caseSensitive; }
	void setCaseSensitive(bool cs) { caseSensitive = cs; }
signals:
	void doubleClickInTreeView(int);
private:
	QList<MTR::SBook>* slist;
	QLineEdit* le;
	QComboBox* qcb;
	myModel* model;
	myView* qtv;
	QGridLayout* qvb;
	QLabel* label;
	bool caseSensitive;
        QRadioButton* radioOne;
	QRadioButton* radioTwo;
};

#endif

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Then you have mymvc.cpp

#include "mymvc.h"
#include "myView.h"
#include "sbook.h"
#include "myModel.h"
#include "myHeaderView.h"
#include <QList>
#include <QGridLayout>
#include <QLabel>
#include <QLineEdit>
#include <QComboBox>
#include <QRadioButton>
 
MyMVC::MyMVC(QList<MTR::Book>* list, QWidget* parent) {
	slist = new QList<MTR::SBook>();
	for(int i = 0;i<list->size();++i) {
		slist->append(MTR::SBook(i,list->value(i)));
	}
   setFixedSize(590,400);
 
   le = new QLineEdit();
   qcb = new QComboBox();
   qcb->addItem(tr("filter by Title"));
   qcb->addItem(tr("filter by Author"));
   qcb->addItem(tr("filter by Publisher"));
   qcb->setCurrentIndex(0);
 
   model = new myModel(*slist,le,qcb);
	model->filter();
 
   qtv = new myView(model);
	qtv->header()->setSortIndicator(0,Qt::DescendingOrder);
 
   label = new QLabel(tr("Enter a character string below"));
   //radioOne = new QRadioButton(tr("Case Sensitive - TRUE"));
   //radioTwo = new QRadioButton(tr("Case Sensitive - FALSE"));
	//radioOne->setChecked(true);
	caseSensitive = true;
   qvb = new QGridLayout();
	//connect(radioOne,SIGNAL(toggled(bool)),this,SLOT(setCaseSensitive(bool)));
   connect(qcb,SIGNAL(currentIndexChanged(int)),le,SLOT(clear()));
   connect(qcb,SIGNAL(currentIndexChanged(int)),qtv,SLOT(filter()));
   connect(le,SIGNAL(textChanged(const QString &)),qtv,SLOT(filter()));
   connect(model,SIGNAL(fromTVtoVM(int)),this,SIGNAL(doubleClickInTreeView(int)));
 
   qvb->addWidget(label,0,0);
   //qvb->addWidget(radioOne,0,1);
   qvb->addWidget(le,1,0);
   //qvb->addWidget(radioTwo,1,1);
   qvb->addWidget(qcb,2,0,1,2);
   qvb->addWidget(qtv,3,0,1,2);
   setLayout(qvb);
}
 
void MyMVC::prodModel(QList<MTR::Book>* list) {
	slist->clear();
	for(int i = 0;i<list->size();++i) {
		slist->append(MTR::SBook(i,list->value(i)));
	}
	model->setInternalList(*slist);
   qcb->setCurrentIndex(0);
	qtv->filter();
 
}

#include "mymvc.h"
#include "myView.h"
#include "sbook.h"
#include "myModel.h"
#include "myHeaderView.h"
#include <QList>
#include <QGridLayout>
#include <QLabel>
#include <QLineEdit>
#include <QComboBox>
#include <QRadioButton>

MyMVC::MyMVC(QList<MTR::Book>* list, QWidget* parent) {
	slist = new QList<MTR::SBook>();
	for(int i = 0;i<list->size();++i) {
		slist->append(MTR::SBook(i,list->value(i)));
	}
   setFixedSize(590,400);

   le = new QLineEdit();
   qcb = new QComboBox();
   qcb->addItem(tr("filter by Title"));
   qcb->addItem(tr("filter by Author"));
   qcb->addItem(tr("filter by Publisher"));
   qcb->setCurrentIndex(0);

   model = new myModel(*slist,le,qcb);
	model->filter();
	
   qtv = new myView(model);
	qtv->header()->setSortIndicator(0,Qt::DescendingOrder);

   label = new QLabel(tr("Enter a character string below"));
   //radioOne = new QRadioButton(tr("Case Sensitive - TRUE"));
   //radioTwo = new QRadioButton(tr("Case Sensitive - FALSE"));
	//radioOne->setChecked(true);
	caseSensitive = true;
   qvb = new QGridLayout();
	//connect(radioOne,SIGNAL(toggled(bool)),this,SLOT(setCaseSensitive(bool)));
   connect(qcb,SIGNAL(currentIndexChanged(int)),le,SLOT(clear()));
   connect(qcb,SIGNAL(currentIndexChanged(int)),qtv,SLOT(filter()));
   connect(le,SIGNAL(textChanged(const QString &)),qtv,SLOT(filter()));
   connect(model,SIGNAL(fromTVtoVM(int)),this,SIGNAL(doubleClickInTreeView(int)));

   qvb->addWidget(label,0,0);
   //qvb->addWidget(radioOne,0,1);
   qvb->addWidget(le,1,0);
   //qvb->addWidget(radioTwo,1,1);
   qvb->addWidget(qcb,2,0,1,2);
   qvb->addWidget(qtv,3,0,1,2);
   setLayout(qvb);
}

void MyMVC::prodModel(QList<MTR::Book>* list) {
	slist->clear();
	for(int i = 0;i<list->size();++i) {
		slist->append(MTR::SBook(i,list->value(i)));
	}
	model->setInternalList(*slist);
   qcb->setCurrentIndex(0);
	qtv->filter();

}

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So my question is simple: what is going on... ?

[jpn]

Could you paste backtrace from debugger?

[mtrpoland]

Aye, here you have:

======= Backtrace: =========
/lib/tls/i686/cmov/libc.so.6[0xb72a6ceb]
/lib/tls/i686/cmov/libc.so.6[0xb72a8ecd]
/lib/tls/i686/cmov/libc.so.6(malloc+0x7f)[0xb72aa83f]
/lib/tls/i686/cmov/libc.so.6[0xb7258c79]
/lib/tls/i686/cmov/libc.so.6(iconv_open+0x1aa)[0xb725870a]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtCore.so.4[0xb7656094]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtCore.so.4[0xb76568d7]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtCore.so.4(_ZN7QString13fromLocal8BitEPKci+0x6a)[0xb75b395a]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtCore.so.4(_ZN16QCoreApplication9argumentsEv+0x73)[0xb762a2e3]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtGui.so.4[0xb79fae7d]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtGui.so.4[0xb79fbad6]
/usr/lib/libSM.so.6(_SmcProcessMessage+0xe3c)[0xb7876924]
/usr/lib/libICE.so.6(IceProcessMessages+0x3c0)[0xb78694c6]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtGui.so.4[0xb79f48f8]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtGui.so.4[0xb79f4977]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtCore.so.4(_ZN11QMetaObject8activateEP7QObjectiiPPv+0x688)[0xb7639908]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtCore.so.4(_ZN11QMetaObject8activateEP7QObjectPKS_iPPv+0x3a)[0xb763a28a]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtCore.so.4(_ZN15QSocketNotifier9activatedEi+0x43)[0xb7658f03]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtCore.so.4(_ZN15QSocketNotifier5eventEP6QEvent+0x24f)[0xb76409af]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtGui.so.4(_ZN19QApplicationPrivate13notify_helperEP7QObjectP6QEvent+0x180)[0xb79a7230]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtGui.so.4(_ZN12QApplication6notifyEP7QObjectP6QEvent+0x111)[0xb79a9961]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtCore.so.4[0xb764b51f]
/usr/lib/libglib-2.0.so.0(g_main_context_dispatch+0x182)[0xb74c9802]
/usr/lib/libglib-2.0.so.0[0xb74cc7df]
/usr/lib/libglib-2.0.so.0(g_main_context_iteration+0x65)[0xb74ccd45]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtCore.so.4(_ZN20QEventDispatcherGlib13processEventsE6QFlagsIN10QEventLoop17ProcessEventsFlagEE+0x58)[0xb764ba68]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtGui.so.4[0xb7a26595]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtCore.so.4(_ZN10QEventLoop13processEventsE6QFlagsINS_17ProcessEventsFlagEE+0x31)[0xb76272e1]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtCore.so.4(_ZN10QEventLoop4execE6QFlagsINS_17ProcessEventsFlagEE+0x7a)[0xb76273ea]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtCore.so.4(_ZN16QCoreApplication4execEv+0xa8)[0xb76297e8]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtGui.so.4(_ZN12QApplication4execEv+0x27)[0xb79a6cf7]
./PL09[0x80527ac]
/lib/tls/i686/cmov/libc.so.6(__libc_start_main+0xdc)[0xb72578cc]
./PL09(_ZN6QFrame10paintEventEP11QPaintEvent+0x31)[0x8051311]
======= Memory map: ========
(...)
Aborted (core dumped)

======= Backtrace: =========
/lib/tls/i686/cmov/libc.so.6[0xb72a6ceb]
/lib/tls/i686/cmov/libc.so.6[0xb72a8ecd]
/lib/tls/i686/cmov/libc.so.6(malloc+0x7f)[0xb72aa83f]
/lib/tls/i686/cmov/libc.so.6[0xb7258c79]
/lib/tls/i686/cmov/libc.so.6(iconv_open+0x1aa)[0xb725870a]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtCore.so.4[0xb7656094]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtCore.so.4[0xb76568d7]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtCore.so.4(_ZN7QString13fromLocal8BitEPKci+0x6a)[0xb75b395a]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtCore.so.4(_ZN16QCoreApplication9argumentsEv+0x73)[0xb762a2e3]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtGui.so.4[0xb79fae7d]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtGui.so.4[0xb79fbad6]
/usr/lib/libSM.so.6(_SmcProcessMessage+0xe3c)[0xb7876924]
/usr/lib/libICE.so.6(IceProcessMessages+0x3c0)[0xb78694c6]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtGui.so.4[0xb79f48f8]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtGui.so.4[0xb79f4977]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtCore.so.4(_ZN11QMetaObject8activateEP7QObjectiiPPv+0x688)[0xb7639908]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtCore.so.4(_ZN11QMetaObject8activateEP7QObjectPKS_iPPv+0x3a)[0xb763a28a]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtCore.so.4(_ZN15QSocketNotifier9activatedEi+0x43)[0xb7658f03]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtCore.so.4(_ZN15QSocketNotifier5eventEP6QEvent+0x24f)[0xb76409af]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtGui.so.4(_ZN19QApplicationPrivate13notify_helperEP7QObjectP6QEvent+0x180)[0xb79a7230]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtGui.so.4(_ZN12QApplication6notifyEP7QObjectP6QEvent+0x111)[0xb79a9961]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtCore.so.4[0xb764b51f]
/usr/lib/libglib-2.0.so.0(g_main_context_dispatch+0x182)[0xb74c9802]
/usr/lib/libglib-2.0.so.0[0xb74cc7df]
/usr/lib/libglib-2.0.so.0(g_main_context_iteration+0x65)[0xb74ccd45]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtCore.so.4(_ZN20QEventDispatcherGlib13processEventsE6QFlagsIN10QEventLoop17ProcessEventsFlagEE+0x58)[0xb764ba68]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtGui.so.4[0xb7a26595]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtCore.so.4(_ZN10QEventLoop13processEventsE6QFlagsINS_17ProcessEventsFlagEE+0x31)[0xb76272e1]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtCore.so.4(_ZN10QEventLoop4execE6QFlagsINS_17ProcessEventsFlagEE+0x7a)[0xb76273ea]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtCore.so.4(_ZN16QCoreApplication4execEv+0xa8)[0xb76297e8]
/usr/local/Trolltech/Qt-4.2.3/lib/libQtGui.so.4(_ZN12QApplication4execEv+0x27)[0xb79a6cf7]
./PL09[0x80527ac]
/lib/tls/i686/cmov/libc.so.6(__libc_start_main+0xdc)[0xb72578cc]
./PL09(_ZN6QFrame10paintEventEP11QPaintEvent+0x31)[0x8051311]
======= Memory map: ========
(...)
Aborted (core dumped)

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[mtrpoland]

and gdb backtrace:

(gdb) backtrace
#0  0xffffe410 in __kernel_vsyscall ()
#1  0xb72ab770 in raise () from /lib/tls/i686/cmov/libc.so.6
#2  0xb72acef3 in abort () from /lib/tls/i686/cmov/libc.so.6
#3  0xb72e0d0b in __fsetlocking () from /lib/tls/i686/cmov/libc.so.6
#4  0xb72e6ceb in malloc_usable_size () from /lib/tls/i686/cmov/libc.so.6
#5  0xb72e8ecd in free () from /lib/tls/i686/cmov/libc.so.6
#6  0xb72ea83f in malloc () from /lib/tls/i686/cmov/libc.so.6
#7  0xb7298c79 in iconv_close () from /lib/tls/i686/cmov/libc.so.6
#8  0xb729870a in iconv_open () from /lib/tls/i686/cmov/libc.so.6
#9  0xb7696094 in QIconvCodec::createIconv_t (to=0xb76c0ced "UTF-16",
    from=0x6 <Address 0x6 out of bounds>) at codecs/qiconvcodec.cpp:227
#10 0xb76968d7 in QIconvCodec::convertToUnicode (this=0x80a7260,
    chars=0xbf84a823 "/home/mtr/Programowanie/Projekty/PersonalLibrarianProject/PL09", len=62) at codecs/qiconvcodec.cpp:68
#11 0xb75f395a in QString::fromLocal8Bit (
    str=0xbf84a823 "/home/mtr/Programowanie/Projekty/PersonalLibrarianProject/PL09", size=62) at ../../include/QtCore/../../src/corelib/codecs/qtextcodec.h:94
#12 0xb766a2e3 in QCoreApplication::arguments ()
    at kernel/qcoreapplication.cpp:1621
#13 0xb7a3ae7d in sm_performSaveYourself (smd=0x81089a0)
    at kernel/qapplication_x11.cpp:4711
#14 0xb7a3bad6 in sm_saveYourselfCallback (smcConn=0x8107fc0,
    clientData=0x81089a0, saveType=1, shutdown=0, interactStyle=0)

(gdb) backtrace
#0  0xffffe410 in __kernel_vsyscall ()
#1  0xb72ab770 in raise () from /lib/tls/i686/cmov/libc.so.6
#2  0xb72acef3 in abort () from /lib/tls/i686/cmov/libc.so.6
#3  0xb72e0d0b in __fsetlocking () from /lib/tls/i686/cmov/libc.so.6
#4  0xb72e6ceb in malloc_usable_size () from /lib/tls/i686/cmov/libc.so.6
#5  0xb72e8ecd in free () from /lib/tls/i686/cmov/libc.so.6
#6  0xb72ea83f in malloc () from /lib/tls/i686/cmov/libc.so.6
#7  0xb7298c79 in iconv_close () from /lib/tls/i686/cmov/libc.so.6
#8  0xb729870a in iconv_open () from /lib/tls/i686/cmov/libc.so.6
#9  0xb7696094 in QIconvCodec::createIconv_t (to=0xb76c0ced "UTF-16",
    from=0x6 <Address 0x6 out of bounds>) at codecs/qiconvcodec.cpp:227
#10 0xb76968d7 in QIconvCodec::convertToUnicode (this=0x80a7260,
    chars=0xbf84a823 "/home/mtr/Programowanie/Projekty/PersonalLibrarianProject/PL09", len=62) at codecs/qiconvcodec.cpp:68
#11 0xb75f395a in QString::fromLocal8Bit (
    str=0xbf84a823 "/home/mtr/Programowanie/Projekty/PersonalLibrarianProject/PL09", size=62) at ../../include/QtCore/../../src/corelib/codecs/qtextcodec.h:94
#12 0xb766a2e3 in QCoreApplication::arguments ()
    at kernel/qcoreapplication.cpp:1621
#13 0xb7a3ae7d in sm_performSaveYourself (smd=0x81089a0)
    at kernel/qapplication_x11.cpp:4711
#14 0xb7a3bad6 in sm_saveYourselfCallback (smcConn=0x8107fc0,
    clientData=0x81089a0, saveType=1, shutdown=0, interactStyle=0)

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[jacek]

#9 0xb7696094 in QIconvCodec::createIconv_t (to=0xb76c0ced "UTF-16",
from=0x6 <Address 0x6 out of bounds>) at codecs/qiconvcodec.cpp:227
#10 0xb76968d7 in QIconvCodec::convertToUnicode (this=0x80a7260, chars=0xbf84a823 "/home/mtr/Programowanie/Projekty/PersonalLibrarianProject/PL09", len=62) at codecs/qiconvcodec.cpp:68

What is that QIconvCodec? What does convertToUnicode() pass as the from parameter to createIconv_t()? It seems that there's a null pointer somewhere.

[marcel]

I think the problem is in the setCaseSensitive slot.
Could you post the code for it?

EDIT: no, forget about that

[jpn]

What is that QIconvCodec? What does convertToUnicode() pass as the from parameter to createIconv_t()? It seems that there's a null pointer somewhere.

Internals of Qt:

#if defined(Q_OS_HPUX)
#  define NO_BOM
#  define UTF16 "ucs2"
#elif defined(Q_OS_AIX)
#  define NO_BOM
#  define UTF16 "UCS-2"
#else
#  define UTF16 "UTF-16"
#endif
 
...
 
QString QIconvCodec::convertToUnicode(const char* chars, int len, ConverterState *) const
{
    if (utf16Codec == reinterpret_cast<QTextCodec *>(~0))
        return QString::fromAscii(chars, len);
 
    iconv_t cd = createIconv_t(UTF16, 0); // <---
    ...
}
 
...
 
iconv_t QIconvCodec::createIconv_t(const char *to, const char *from)
{
    Q_ASSERT((to == 0 && from != 0) || (to != 0 && from == 0));
 
    iconv_t cd = (iconv_t) -1;
#if defined(__GLIBC__) || defined(GNU_LIBICONV)
    // both GLIBC and libgnuiconv will use the locale's encoding if from or to is an empty string
    char *codeset = "";
    cd = iconv_open(to ? to : codeset, from ? from : codeset); // <---
#else
    char *codeset = 0;
#endif
   ...
}

#if defined(Q_OS_HPUX)
#  define NO_BOM
#  define UTF16 "ucs2"
#elif defined(Q_OS_AIX)
#  define NO_BOM
#  define UTF16 "UCS-2"
#else
#  define UTF16 "UTF-16"
#endif

...

QString QIconvCodec::convertToUnicode(const char* chars, int len, ConverterState *) const
{
    if (utf16Codec == reinterpret_cast<QTextCodec *>(~0))
        return QString::fromAscii(chars, len);

    iconv_t cd = createIconv_t(UTF16, 0); // <---
    ...
}

...

iconv_t QIconvCodec::createIconv_t(const char *to, const char *from)
{
    Q_ASSERT((to == 0 && from != 0) || (to != 0 && from == 0));

    iconv_t cd = (iconv_t) -1;
#if defined(__GLIBC__) || defined(GNU_LIBICONV)
    // both GLIBC and libgnuiconv will use the locale's encoding if from or to is an empty string
    char *codeset = "";
    cd = iconv_open(to ? to : codeset, from ? from : codeset); // <---
#else
    char *codeset = 0;
#endif
   ...
}

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[jacek]

iconv_t cd = createIconv_t(UTF16, 0); // <---

to=0xb76c0ced "UTF-16", from=0x6 <Address 0x6 out of bounds>

Something is fishy around here. Maybe the library was corrupted?

[pdolbey]

Lets see if I undertstand this code.

iconv_t cd = createIconv_t(UTF16, 0);

iconv_t cd = createIconv_t(UTF16, 0);

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In reality your traceback implies you mean

iconv_t cd = createIconv_t("UTF-16", NULL);

iconv_t cd = createIconv_t("UTF-16", NULL);

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yet you get

0xb7696094 in QIconvCodec::createIconv_t (to=0xb76c0ced "UTF-16",    
from=0x6 <Address 0x6 out of bounds>) at codecs/qiconvcodec.cpp:227

0xb7696094 in QIconvCodec::createIconv_t (to=0xb76c0ced "UTF-16",    
from=0x6 <Address 0x6 out of bounds>) at codecs/qiconvcodec.cpp:227

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Why do you get 0x6 then? I suggest you re-try using the NULL macro instead of 0.

Pete

[mtrpoland]

So yo advise me to change the line:

iconv_t cd = createIconv_t(UTF16, 0);

iconv_t cd = createIconv_t(UTF16, 0);

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that is placed in some qt file
to

iconv_t cd = createIconv_t(UTF16, NULL);

iconv_t cd = createIconv_t(UTF16, NULL);

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??
Just don't get the idea why my actions that are actually a commonplace (initialization of two QRadioButton's and its usage) entail a problem I presented above.
It's quite bizarre.

[jacek]

Just don't get the idea why my actions that are actually a commonplace (initialization of two QRadioButton's and its usage) entail a problem I presented above.
It's quite bizarre.

Yes, it is. Can you reproduce that stack trace?

[mtrpoland]

What do you mean by "reproducing the stack trace" ?

[jacek]

Why do you get 0x6 then? I suggest you re-try using the NULL macro instead of 0.

The problematic code appears to be a part of Qt and it seems perfectly valid. Furthermore there's an assertion in QIconvCodec::createIconv_t() that should detect this situation.


BTW. There is no such thing as NULL macro in C++, it's defined only for compatibility with C.

[pdolbey]

BTW. There is no such thing as NULL macro in C++, it's defined only for compatibility with C.

Apparently (and I've only just googled for this)

The standard says that NULL exists, but is implementation-defined.

Section 18.1, line 4 :

"The macro NULL is an implementation-defined C + + null pointer constant
in this International Standard (4.10)."

It also mentions that it is defined in <cstddef>.

Section 4.10 starts by defining a "null pointer constant" :

"A null pointer constant is an integral constant expression (5.19)
rvalue of integer type that evaluates to zero."

In C++ NULL is typically either 0 or 0L (but not ((void*)0) - I was basically suggesting replacing 0 with NULL as I couldn't see any logical reason why the function call should transform '0' into '0x6' unless it was an compiler "implementation" gotcha. I'd always prefer NULL over 0 but thats because I think its more readable, but there seems to be many opinions on this matter.

I didn't realise how deep this problem was in the Qt4 source code as I don't remember seeing the class QIconvCodec in the public API - just found it in the source tree.

Pete

[jacek]

It also mentions that it is defined in <cstddef>.

Exactly, as I said, it's only for compatibility with C. In the new C++ standard, there will be a nullptr constant, but for now the first paragraph in section 4.10 says: "A null pointer constant is an integral constant expression (5.19) rvalue of integer type that evaluates to zero."

I couldn't see any logical reason why the function call should transform '0' into '0x6' unless it was an compiler "implementation" gotcha.

It could be, but 0 is used as a null pointer in many places in Qt sources, so it shouldn't be a problem.

I'd always prefer NULL over 0 but thats because I think its more readable, but there seems to be many opinions on this matter.

It also causes some problems with templates.

I don't remember seeing the class QIconvCodec in the public API

Neither did I. You can learn new things about Qt every day.