<QtGlobal> - Global Qt Declarations

void qFatal ( const char * msg, ... )

Calls the message handler with the fatal message msg. If no message handler has been installed, the message is printed to stderr. Under Windows, the message is sent to the debugger.

If you are using the default message handler this function will abort on Unix systems to create a core dump. On Windows, for debug builds, this function will report a _CRT_ERROR enabling you to connect a debugger to the application.

This function takes a format string and a list of arguments, similar to the C printf() function.

Example:

 int divide(int a, int b)
 {
     if (b == 0)                                // program error
         qFatal("divide: cannot divide by zero");
     return a / b;
 }

To supress the output at runtime, install your own message handler with qInstallMsgHandler().

See also qDebug(), qCritical(), qWarning(), qInstallMsgHandler(), and Debugging Techniques.

bool qFuzzyCompare ( double p1, double p2 )   [static]

Compares the floating point value p1 and p2 and returns true if they are considered equal, otherwise false.

Note that comparing values where either p1 or p2 is 0.0 will not work. The solution to this is to compare against values greater than or equal to 1.0.

         // Instead of comparing with 0.0
                 qFuzzyCompare(0.0,1.0e-200); // This will return false
         // Compare adding 1 to both values will fix the problem
                 qFuzzyCompare(1 + 0.0, 1 + 1.0e-200); // This will return true

The two numbers are compared in a relative way, where the exactness is stronger the smaller the numbers are.

Note: This function is thread-safe.

This function was introduced in Qt 4.4.

bool qFuzzyCompare ( float p1, float p2 )   [static]

Compares the floating point value p1 and p2 and returns true if they are considered equal, otherwise false.

The two numbers are compared in a relative way, where the exactness is stronger the smaller the numbers are.

Note: This function is thread-safe.

This function was introduced in Qt 4.4.

 #include <qapplication.h>
 #include <stdio.h>
 #include <stdlib.h>

 void myMessageOutput(QtMsgType type, const char *msg)
 {
     switch (type) {
     case QtDebugMsg:
         fprintf(stderr, "Debug: %s\n", msg);
         break;
     case QtWarningMsg:
         fprintf(stderr, "Warning: %s\n", msg);
         break;
     case QtCriticalMsg:
         fprintf(stderr, "Critical: %s\n", msg);
         break;
     case QtFatalMsg:
         fprintf(stderr, "Fatal: %s\n", msg);
         abort();
     }
 }

 int main(int argc, char **argv)
 {
     qInstallMsgHandler(myMessageOutput);
     QApplication app(argc, argv);
     ...
     return app.exec();
 }

 int myValue = 6;
 int yourValue = 4;

 int maxValue = qMax(myValue, yourValue);
 // maxValue == myValue

 int myValue = 6;
 int yourValue = 4;

 int minValue = qMin(myValue, yourValue);
 // minValue == yourValue

 qreal valueA = 42949672960.3;
 qreal valueB = 42949672960.7;

 int roundedValueA = qRound(valueA);
 // roundedValueA = 42949672960
 int roundedValueB = qRound(valueB);
 // roundedValueB = 42949672961

 qreal valueA = 2.3;
 qreal valueB = 2.7;

 int roundedValueA = qRound(valueA);
 // roundedValueA = 2
 int roundedValueB = qRound(valueB);
 // roundedValueB = 3

 void f(int c)
 {
     if (c > 200)
         qWarning("f: bad argument, c == %d", c);
 }

 qWarning() << "Brush:" << myQBrush << "Other value:"
 << i;

     //% "%n fooish bar(s) found.\n"
     //% "Do you want to continue?"
     QString text = qtTrId("qtn_foo_bar", n);

 #include <QApplication>
 #include <QMessageBox>

 int main(int argc, char *argv[])
 {
     QT_REQUIRE_VERSION(argc, argv, "4.0.2")

     QApplication app(argc, argv);
     ...
     return app.exec();
 }

 static { const char *source; const char *comment; } greeting_strings[] =
 {
     QT_TRANSLATE_NOOP3("FriendlyConversation", "Hello",
                        "A really friendly hello"),
     QT_TRANSLATE_NOOP3("FriendlyConversation", "Goodbye",
                        "A really friendly goodbye")
 };

 QString FriendlyConversation::greeting(int type)
 {
     return tr(greeting_strings[type].source,
               greeting_strings[type].comment);
 }

 QString global_greeting(int type)
 {
     return qApp->translate("FriendlyConversation",
            greeting_strings[type].source,
            greeting_strings[type].comment);
 }

 static const char *greeting_strings[] = {
     QT_TRANSLATE_NOOP("FriendlyConversation", "Hello"),
     QT_TRANSLATE_NOOP("FriendlyConversation", "Goodbye")
 };

 QString FriendlyConversation::greeting(int type)
 {
     return tr(greeting_strings[type]);
 }

 QString global_greeting(int type)
 {
     return qApp->translate("FriendlyConversation",
            greeting_strings[type]);
 }

 // A Symbian leaving function is being called within a Qt function.
 // Any leave must be converted to an exception
 CAknTitlePane* titlePane = S60->titlePane();
 if (titlePane) {
     TPtrC captionPtr(qt_QString2TPtrC(caption));
     QT_TRAP_THROWING(titlePane->SetTextL(captionPtr));
 }

 static const char * const ids[] = {
     //% "This is the first text."
     QT_TRID_NOOP("qtn_1st_text"),
     //% "This is the second text."
     QT_TRID_NOOP("qtn_2nd_text"),
     0
 };

 void TheClass::addLabels()
 {
     for (int i = 0; ids[i]; ++i)
         new QLabel(qtTrId(ids[i]), this);
 }

 // An exception might be thrown in this Symbian TInt error returning function.
 // It is caught and translated to an error code
 TInt QServerApp::Connect(const QString &serverName)
 {
     TPtrC name;
     TInt err;
     QT_TRYCATCH_ERROR(err, name.Set(qt_QString2TPtrC(serverName)));
     if (err != KErrNone)
         return err;
     return iServer.Connect(name);
 }

 // This active object signals Qt code
 // Exceptions from the Qt code must be converted to Symbian OS leaves for the active scheduler
 void QWakeUpActiveObject::RunL()
 {
     iStatus = KRequestPending;
     SetActive();
     QT_TRYCATCH_LEAVING(m_dispatcher->wakeUpWasCalled());
 }

 QString FriendlyConversation::greeting(int type)
 {
 static const char *greeting_strings[] = {
     QT_TR_NOOP("Hello"),
     QT_TR_NOOP("Goodbye")
 };
 return tr(greeting_strings[type]);
 }

 #if QT_VERSION >= 0x040100
     QIcon icon = style()->standardIcon(QStyle::SP_TrashIcon);
 #else
     QPixmap pixmap = style()->standardPixmap(QStyle::SP_TrashIcon);
     QIcon icon(pixmap);
 #endif

 // File: div.cpp

 #include <QtGlobal>

 int divide(int a, int b)
 {
     Q_ASSERT(b != 0);
     return a / b;
 }

 ASSERT: "b == 0" in file div.cpp, line 7

 // File: div.cpp

 #include <QtGlobal>

 int divide(int a, int b)
 {
     Q_ASSERT_X(b != 0, "divide", "division by zero");
     return a / b;
 }

 ASSERT failure in divide: "division by zero", file div.cpp, line 7

 #if Q_BYTE_ORDER == Q_BIG_ENDIAN
 ...
 #endif

 #if Q_BYTE_ORDER == Q_BIG_ENDIAN
 ...
 #endif

 or

 #if Q_BYTE_ORDER == Q_LITTLE_ENDIAN
 ...
 #endif

 int *a;

 Q_CHECK_PTR(a = new int[80]);   // WRONG!

 a = new (nothrow) int[80];      // Right
 Q_CHECK_PTR(a);

 struct Point2D
 {
     int x;
     int y;
 };

 Q_DECLARE_TYPEINFO(Point2D, Q_PRIMITIVE_TYPE);

 class Point2D
 {
 public:
     Point2D() { data = new int[2]; }
     Point2D(const Point2D &other) { ... }
     ~Point2D() { delete[] data; }

     Point2D &operator=(const Point2D &other) { ... }

     int x() const { return data[0]; }
     int y() const { return data[1]; }

 private:
     int *data;
 };

 Q_DECLARE_TYPEINFO(Point2D, Q_MOVABLE_TYPE);

 template<typename TInputType>
 const TInputType &myMin(const TInputType &value1, const TInputType &value2)
 {
     qDebug() << Q_FUNC_INFO << "was called with value1:" << value1 << "value2:" << value2;

     if(value1 < value2)
         return value1;
     else
         return value2;
 }

 qint64 value = Q_INT64_C(932838457459459);

 #if Q_BYTE_ORDER == Q_LITTLE_ENDIAN
 ...
 #endif

 quint64 value = Q_UINT64_C(932838457459459);

 CONFIG += no_keywords

 forever {
     ...
 }

 CONFIG += no_keywords

 qWarning("%s: %s", qPrintable(key), qPrintable(value));