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# <QtGlobal> - Global Qt Declarations

The <QtGlobal> header file provides basic declarations and is included by all other Qt headers. More...

### Types

- typedef qint8
- typedef qint16
- typedef qint32
- typedef qint64
- typedef qlonglong
- typedef qreal
- typedef quint8
- typedef quint16
- typedef quint32
- typedef quint64
- typedef qulonglong
- typedef uchar
- typedef uint
- typedef ulong
- typedef ushort

### Functions

- T qAbs ( const T & value )
- const T & qBound ( const T & min, const T & value, const T & max )
- void qCritical ( const char * msg, ... )
- void qDebug ( const char * msg, ... )
- void qFatal ( const char * msg, ... )
- QtMsgHandler qInstallMsgHandler ( QtMsgHandler h )
- int qMacVersion ()
- const T & qMax ( const T & value1, const T & value2 )
- const T & qMin ( const T & value1, const T & value2 )
- qint64 qRound64 ( double value )
- int qRound ( double value )
- const char * qVersion ()
- void qWarning ( const char * msg, ... )

### Macros

- const char * QT_TRANSLATE_NOOP ( const char * context, const char * sourceText )
- const char * QT_TR_NOOP ( const char * sourceText )
- void Q_ASSERT ( bool test )
- void Q_ASSERT_X ( bool test, const char * where, const char * what )
- void Q_CHECK_PTR ( void * p )
- Q_FOREACH ( variable, container )
- qint64 Q_INT64_C ( literal )
- quint64 Q_UINT64_C ( literal )
- foreach ( variable, container )

## Detailed Description

The <QtGlobal> header file provides basic declarations and is included by all other Qt headers.

See also <QtAlgorithms>.

## Type Documentation

### typedef qint8

Typedef for `signed char`. This type is guaranteed to be 8-bit on all platforms supported by Qt.

### typedef qint16

Typedef for `signed short`. This type is guaranteed to be 16-bit on all platforms supported by Qt.

### typedef qint32

Typedef for `signed int`. This type is guaranteed to be 32-bit on all platforms supported by Qt.

### typedef qint64

Typedef for `long long int` (`__int64` on Windows). This type is guaranteed to be 64-bit on all platforms supported by Qt.

Literals of that type can be created using the Q_INT64_C() macro:

        qint64 value = Q_INT64_C(932838457459459);

See also Q_INT64_C() and quint64.

### typedef qlonglong

Typedef for `long long int` (`__int64` on Windows). This is the same as qint64.

See also Q_INT64_C() and qulonglong.

### typedef qreal

Typedef for `double`.

### typedef quint8

Typedef for `unsigned signed char`. This type is guaranteed to be 8-bit on all platforms supported by Qt.

### typedef quint16

Typedef for `unsigned signed short`. This type is guaranteed to be 16-bit on all platforms supported by Qt.

### typedef quint32

Typedef for `unsigned signed int`. This type is guaranteed to be 32-bit on all platforms supported by Qt.

### typedef quint64

Typedef for `unsigned long long int` (`unsigned __int64` on Windows). This type is guaranteed to be 64-bit on all platforms supported by Qt.

Literals of that type can be created using the Q_UINT64_C() macro:

        quint64 value = Q_UINT64_C(932838457459459);

See also Q_UINT64_C() and qint64.

### typedef qulonglong

Typedef for `unsigned long long int` (`unsigned __int64` on Windows). This is the same as quint64.

See also Q_UINT64_C() and qlonglong.

### typedef uchar

Convenience typedef for `unsigned char`.

### typedef uint

Convenience typedef for `unsigned int`.

### typedef ulong

Convenience typedef for `unsigned long`.

### typedef ushort

Convenience typedef for `unsigned short`.

## Function Documentation

### T qAbs ( const T & value )

Returns the absolute value of value.

### const T & qBound ( const T & min, const T & value, const T & max )

Returns value bounded by min and max. This is equivalent to qMax(min, qMin(value, max)).

See also qMin() and qMax().

### void qCritical ( const char * msg, ... )

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

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

Example:

        void load(const QString &filename)
        {
            QFile file(filename);
            if (!file.exists())
                qCritical("file '%s' does not exist!", filename.local8bit());
        }

Warning: The internal buffer is limited to 8192 bytes, including the '\0'-terminator.

Warning: Passing (const char *)0 as argument to qCritical might lead to crashes on certain platforms due to the platforms printf implementation.

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

### void qDebug ( const char * msg, ... )

Calls the message handler with the debug message msg. If no message handler has been installed, the message is printed to stderr. Under Windows, the message is sent to the debugger. This function does nothing if `QT_NO_DEBUG_OUTPUT` was defined during compilation.

If you pass the function a format string and a list of arguments, it works in similar way to the C printf() function.

Example:

        qDebug("my window handle = %x", myWidget->id());

A more convenient syntax is also available:

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

This syntax automatically puts a single space between each item, and outputs a newline at the end. It supports many C++ and Qt types.

Warning: The internal buffer is limited to 8192 bytes, including the '\0'-terminator.

Warning: Passing (const char *)0 as argument to qDebug might lead to crashes on certain platforms due to the platform's printf() implementation.

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

### 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.

For a release library this function will exit the application with return value 1. For the debug version this function will abort on Unix systems to create a core dump, and report a _CRT_ERROR on Windows allowing 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;
        }

Warning: The internal buffer is limited to 8192 bytes, including the '\0'-terminator.

Warning: Passing (const char *)0 as argument to qFatal might lead to crashes on certain platforms due to the platforms printf implementation.

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

### QtMsgHandler qInstallMsgHandler ( QtMsgHandler h )

Installs a Qt message handler h. Returns a pointer to the message handler previously defined.

The message handler is a function that prints out debug messages, warnings and fatal error messages. The Qt library (debug version) contains hundreds of warning messages that are printed when internal errors (usually invalid function arguments) occur. If you implement your own message handler, you get total control of these messages.

The default message handler prints the message to the standard output under X11 or to the debugger under Windows. If it is a fatal message, the application aborts immediately.

Only one message handler can be defined, since this is usually done on an application-wide basis to control debug output.

To restore the message handler, call `qInstallMsgHandler(0)`.

Example:

        #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(); // deliberately core dump
            }
        }

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

See also qDebug(), qWarning(), qFatal(), and Debugging Techniques.

### int qMacVersion ()

Use QSysInfo::MacintoshVersion instead.

See also QSysInfo.

### const T & qMax ( const T & value1, const T & value2 )

Returns the maximum of value1 and value2.

See also qMin() and qBound().

### const T & qMin ( const T & value1, const T & value2 )

Returns the minimum of value1 and value2.

See also qMax() and qBound().

### qint64 qRound64 ( double value )

Rounds value up to the nearest 64-bit integer.

### int qRound ( double value )

Rounds value up to the nearest integer.

### const char * qVersion ()

Returns the Qt version number as a string, for example, "4.0.1" or "4.1.3".

The `QT_VERSION` define has the numeric value in the form: 0xMMNNPP (MM = major, NN = minor, PP = patch). For example, Qt 4.0.1's `QT_VERSION` is 0x040001.

### void qWarning ( const char * msg, ... )

Calls the message handler with the warning message msg. If no message handler has been installed, the message is printed to stderr. Under Windows, the message is sent to the debugger. This function does nothing if `QT_NO_WARNING_OUTPUT` was defined during compilation; it exits if the environment variable `QT_FATAL_WARNINGS` is defined.

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

Example:

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

Warning: The internal buffer is limited to 8192 bytes, including the '\0'-terminator.

Warning: Passing (const char *)0 as argument to qWarning might lead to crashes on certain platforms due to the platforms printf implementation.

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

## Macro Documentation

### const char * QT_TRANSLATE_NOOP ( const char * context, const char * sourceText )

Marks the string literal sourceText for translation in the given context. Expands to sourceText.

Example:

        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]);
        }

See also QT_TR_NOOP() and Internationalization with Qt.

### const char * QT_TR_NOOP ( const char * sourceText )

Marks the string literal sourceText for translation in the current context. Expands to sourceText.

Example:

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

See also QT_TRANSLATE_NOOP() and Internationalization with Qt.

### void Q_ASSERT ( bool test )

Prints a warning message containing the source code file name and line number if test is false.

Q_ASSERT() is useful for testing pre- and post-conditions during development. It does nothing if `QT_NO_DEBUG` was defined during compilation.

Example:

        //
        // File: div.cpp
        //

        #include <QtGlobal>

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

If `b` is zero, the Q_ASSERT statement will output the following message using the qFatal() function:

        ASSERT: "b == 0" in file div.cpp, line 9

See also Q_ASSERT_X(), qFatal(), and Debugging Techniques.

### void Q_ASSERT_X ( bool test, const char * where, const char * what )

Prints the message what together with the location where, the source file name and line number if test is false.

Q_ASSERT_X is useful for testing pre- and post-conditions during development. It does nothing if `QT_NO_DEBUG` was defined during compilation.

Example:

        //
        // File: div.cpp
        //

        #include <QtGlobal>

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

If `b` is zero, the Q_ASSERT_X statement will output the following message using the qFatal() function:

        ASSERT failure in divide: "division by zero", file div.cpp, line 9

See also Q_ASSERT(), qFatal(), and Debugging Techniques.

### void Q_CHECK_PTR ( void * p )

If p is 0, prints a warning message containing the source code file name and line number, saying that the program ran out of memory.

Q_CHECK_PTR does nothing if `QT_NO_DEBUG` was defined during compilation.

Example:

        int *a;

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

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

See also qWarning() and Debugging Techniques.

### Q_FOREACH ( variable, container )

Same as foreach(variable, container).

### qint64 Q_INT64_C ( literal )

Wraps the signed 64-bit integer literal in a platform-independent way. For example:

        qint64 value = Q_INT64_C(932838457459459);

See also qint64 and Q_UINT64_C().

### quint64 Q_UINT64_C ( literal )

Wraps the unsigned 64-bit integer literal in a platform-independent way. For example:

        quint64 value = Q_UINT64_C(932838457459459);

See also quint64 and Q_INT64_C().

### foreach ( variable, container )

This macro is used to implement Qt's `foreach` loop. variable is a variable name or variable definition; container is a Qt container whose value type corresponds to the type of the variable. See The foreach Keyword for details.

If you're worried about namespace pollution, you can disable this macro by adding the following line to your `.pro` file:

        CONFIG += no_keywords

See also Q_FOREACH().