<QtGlobal> - Global Qt Declarations The <QtGlobal> header file includes the fundamental global declarations. It is included by most other Qt header files. More... Obsolete members Types typedef QFunctionPointer typedef QtMessageHandler enum QtMsgType { QtDebugMsg, QtInfoMsg, QtWarningMsg, QtCriticalMsg, QtFatalMsg, QtSystemMsg } typedef qint8 typedef qint16 typedef qint32 typedef qint64 typedef qintptr typedef qlonglong typedef qptrdiff typedef qreal typedef quint8 typedef quint16 typedef quint32 typedef quint64 typedef quintptr typedef qulonglong typedef uchar typedef uint typedef ulong typedef ushort Functions T qAbs(const T &value) QtPrivat8b7c:f320:99b9:690f:4595:cd17:293a:c069QAddConst<T>8b7c:f320:99b9:690f:4595:cd17:293a:c069Type & qAsConst(T &t) const T & qBound(const T &min, const T &value, const T &max) auto qConstOverload(T memberFunctionPointer) int qEnvironmentVariableIntValue(const char *varName, bool *ok = Q_NULLPTR) bool qEnvironmentVariableIsEmpty(const char *varName) bool qEnvironmentVariableIsSet(const char *varName) quint32 qFloatDistance(float a, float b) quint64 qFloatDistance(double a, double b) QString qFormatLogMessage(QtMsgType type, const QMessageLogContext &context, const QString &str) bool qFuzzyCompare(double p1, double p2) bool qFuzzyCompare(float p1, float p2) bool qFuzzyIsNull(double d) bool qFuzzyIsNull(float f) double qInf() QtMessageHandler qInstallMessageHandler(QtMessageHandler handler) bool qIsFinite(double d) bool qIsFinite(float f) bool qIsInf(double d) bool qIsInf(float f) bool qIsNaN(double d) bool qIsNaN(float f) const T & qMax(const T &value1, const T &value2) const T & qMin(const T &value1, const T &value2) auto qNonConstOverload(T memberFunctionPointer) auto qOverload(T functionPointer) double qQNaN() qint64 qRound64(double value) qint64 qRound64(float value) int qRound(double value) int qRound(float value) double qSNaN() void qSetMessagePattern(const QString &pattern) T * q_check_ptr(T *pointer) QByteArray qgetenv(const char *varName) bool qputenv(const char *varName, const QByteArray &value) int qrand() void qsrand(uint seed) QString qtTrId(const char *id, int n = -1) bool qunsetenv(const char *varName) Macros QT_DEPRECATED_WARNINGS QT_DISABLE_DEPRECATED_BEFORE QT_POINTER_SIZE QT_REQUIRE_VERSION(int argc, char **argv, const char *version) QT_TRANSLATE_NOOP3(context, sourceText, comment) QT_TRANSLATE_NOOP(context, sourceText) QT_TRID_NOOP(id) QT_TR_NOOP(sourceText) QT_VERSION QT_VERSION_CHECK QT_VERSION_STR void Q_ASSERT(bool test) void Q_ASSERT_X(bool test, const char *where, const char *what) void Q_ASSUME(bool expr) Q_BIG_ENDIAN Q_BYTE_ORDER Q_CC_BOR Q_CC_CDS Q_CC_CLANG Q_CC_COMEAU Q_CC_DEC Q_CC_EDG Q_CC_GHS Q_CC_GNU Q_CC_HIGHC Q_CC_HPACC Q_CC_INTEL Q_CC_KAI Q_CC_MIPS Q_CC_MSVC Q_CC_OC Q_CC_PGI Q_CC_SUN Q_CC_SYM Q_CC_USLC Q_CC_WAT void Q_CHECK_PTR(void *pointer) Q_DECLARE_TYPEINFO(Type, Flags) Q_DECL_CONSTEXPR Q_DECL_EXPORT Q_DECL_FINAL Q_DECL_IMPORT Q_DECL_NOEXCEPT Q_DECL_NOEXCEPT_EXPR(x) Q_DECL_NOTHROW Q_DECL_OVERRIDE Q_DECL_RELAXED_CONSTEXPR void Q_FALLTHROUGH() Q_FOREACH(variable, container) Q_FOREVER Q_FORWARD_DECLARE_CF_TYPE(type) Q_FORWARD_DECLARE_MUTABLE_CF_TYPE(type) Q_FORWARD_DECLARE_OBJC_CLASS(classname) const char * Q_FUNC_INFO() qint64 Q_INT64_C(literal) Q_LIKELY(expr) Q_LITTLE_ENDIAN Q_OS_AIX Q_OS_ANDROID Q_OS_BSD4 Q_OS_BSDI Q_OS_CYGWIN Q_OS_DARWIN Q_OS_DGUX Q_OS_DYNIX Q_OS_FREEBSD Q_OS_HPUX Q_OS_HURD Q_OS_IOS Q_OS_IRIX Q_OS_LINUX Q_OS_LYNX Q_OS_MAC Q_OS_MACOS Q_OS_NETBSD Q_OS_OPENBSD Q_OS_OSF Q_OS_OSX Q_OS_QNX Q_OS_RELIANT Q_OS_SCO Q_OS_SOLARIS Q_OS_TVOS Q_OS_ULTRIX Q_OS_UNIX Q_OS_UNIXWARE Q_OS_WATCHOS Q_OS_WIN32 Q_OS_WIN64 Q_OS_WIN Q_OS_WINRT Q_PROCESSOR_X86 Q_PROCESSOR_S390 Q_PROCESSOR_ALPHA Q_PROCESSOR_ARM Q_PROCESSOR_ARM_V5 Q_PROCESSOR_ARM_V6 Q_PROCESSOR_ARM_V7 Q_PROCESSOR_AVR32 Q_PROCESSOR_BLACKFIN Q_PROCESSOR_IA64 Q_PROCESSOR_MIPS Q_PROCESSOR_MIPS_32 Q_PROCESSOR_MIPS_64 Q_PROCESSOR_MIPS_I Q_PROCESSOR_MIPS_II Q_PROCESSOR_MIPS_III Q_PROCESSOR_MIPS_IV Q_PROCESSOR_MIPS_V Q_PROCESSOR_POWER Q_PROCESSOR_POWER_32 Q_PROCESSOR_POWER_64 Q_PROCESSOR_S390_X Q_PROCESSOR_SH Q_PROCESSOR_SH_4A Q_PROCESSOR_SPARC Q_PROCESSOR_SPARC_V9 Q_PROCESSOR_X86_32 Q_PROCESSOR_X86_64 quint64 Q_UINT64_C(literal) Q_UNLIKELY(expr) void Q_UNREACHABLE() Q_UNUSED(name) foreach(variable, container) forever qCritical(const char *message, ...) qDebug(const char *message, ...) qFatal(const char *message, ...) qInfo(const char *message, ...) qMove(x) const char * qPrintable(const QString &str) const wchar_t * qUtf16Printable(const QString &str) const char * qUtf8Printable(const QString &str) qWarning(const char *message, ...) The global declarations include types, functions and macros. The type definitions are partly convenience definitions for basic types (some of which guarantee certain bit-sizes on all platforms supported by Qt), partly types related to Qt message handling. The functions are related to generating messages, Qt version handling and comparing and adjusting object values. And finally, some of the declared macros enable programmers to add compiler or platform specific code to their applications, while others are convenience macros for larger operations. Types The header file declares several type definitions that guarantee a specified bit-size on all platforms supported by Qt for various basic types, for example qint8 which is a signed char guaranteed to be 8-bit on all platforms supported by Qt. The header file also declares the qlonglong type definition for long long int (__int64 on Windows). Several convenience type definitions are declared: qreal for double, uchar for unsigned char, uint for unsigned int, ulong for unsigned long and ushort for unsigned short. Finally, the QtMsgType definition identifies the various messages that can be generated and sent to a Qt message handler; QtMessageHandler is a type definition for a pointer to a function with the signature void myMessageHandler(QtMsgType, const QMessageLogContext &, const char *). QMessageLogContext class contains the line, file, and function the message was logged at. This information is created by the QMessageLogger class. Functions The <QtGlobal> header file contains several functions comparing and adjusting an object's value. These functions take a template type as argument: You can retrieve the absolute value of an object using the qAbs() function, and you can bound a given object's value by given minimum and maximum values using the qBound() function. You can retrieve the minimum and maximum of two given objects using qMin() and qMax() respectively. All these functions return a corresponding template type; the template types can be replaced by any other type. Example: int myValue = 10; int minValue = 2; int maxValue = 6; int boundedValue = qBound(minValue, myValue, maxValue); // boundedValue == 6 <QtGlobal> also contains functions that generate messages from the given string argument: qDebug(), qInfo(), qWarning(), qCritical(), and qFatal(). These functions call the message handler with the given message. Example: if (!driver()->isOpen() || driver()->isOpenError()) { qWarning("QSqlQuery8b7c:f320:99b9:690f:4595:cd17:293a:c069xec: database not open"); return false; } The remaining functions are qRound() and qRound64(), which both accept a double or float value as their argument returning the value rounded up to the nearest integer and 64-bit integer respectively, the qInstallMessageHandler() function which installs the given QtMessageHandler, and the qVersion() function which returns the version number of Qt at run-time as a string. Macros The <QtGlobal> header file provides a range of macros (Q_CC_*) that are defined if the application is compiled using the specified platforms. For example, the Q_CC_SUN macro is defined if the application is compiled using Forte Developer, or Sun Studio C++. The header file also declares a range of macros (Q_OS_*) that are defined for the specified platforms. For example, Q_OS_UNIX which is defined for the Unix-based systems. The purpose of these macros is to enable programmers to add compiler or platform specific code to their application. The remaining macros are convenience macros for larger operations: The QT_TRANSLATE_NOOP() and QT_TR_NOOP() macros provide the possibility of marking text for dynamic translation, i.e. translation without changing the stored source text. The Q_ASSERT() and Q_ASSERT_X() enables warning messages of various level of refinement. The Q_FOREACH() and foreach() macros implement Qt's foreach loop. The Q_INT64_C() and Q_UINT64_C() macros wrap signed and unsigned 64-bit integer literals in a platform-independent way. The Q_CHECK_PTR() macro prints a warning containing the source code's file name and line number, saying that the program ran out of memory, if the pointer is 0. The qPrintable() and qUtf8Printable() macros represent an easy way of printing text. Finally, the QT_POINTER_SIZE macro expands to the size of a pointer in bytes, and the QT_VERSION and QT_VERSION_STR macros expand to a numeric value or a string, respectively, specifying Qt's version number, i.e the version the application is compiled against. See also <QtAlgorithms> and QSysInfo. Type Documentation typedef QFunctionPointer This is a typedef for void (*)(), a pointer to a function that takes no arguments and returns void. typedef QtMessageHandler This is a typedef for a pointer to a function with the following signature: void myMessageHandler(QtMsgType, const QMessageLogContext &, const QString &); This typedef was introduced in Qt 5.0. See also QtMsgType and qInstallMessageHandler(). enum QtMsgType This enum describes the messages that can be sent to a message handler (QtMessageHandler). You can use the enum to identify and associate the various message types with the appropriate actions. Constant Value Description QtDebugMsg 0 A message generated by the qDebug() function. QtInfoMsg 4 A message generated by the qInfo() function. QtWarningMsg 1 A message generated by the qWarning() function. QtCriticalMsg 2 A message generated by the qCritical() function. QtFatalMsg 3 A message generated by the qFatal() function. QtSystemMsg QtCriticalMsg QtInfoMsg was added in Qt 5.5. See also QtMessageHandler and qInstallMessageHandler(). 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 this type can be created using the Q_INT64_C() macro: qint64 value = Q_INT64_C(932838457459459); See also Q_INT64_C(), quint64, and qlonglong. typedef qintptr Integral type for representing pointers in a signed integer (useful for hashing, etc.). Typedef for either qint32 or qint64. This type is guaranteed to be the same size as a pointer on all platforms supported by Qt. On a system with 32-bit pointers, qintptr is a typedef for qint32; on a system with 64-bit pointers, qintptr is a typedef for qint64. Note that qintptr is signed. Use quintptr for unsigned values. See also qptrdiff, qint32, and qint64. typedef qlonglong Typedef for long long int (__int64 on Windows). This is the same as qint64. See also qulonglong and qint64. typedef qptrdiff Integral type for representing pointer differences. Typedef for either qint32 or qint64. This type is guaranteed to be the same size as a pointer on all platforms supported by Qt. On a system with 32-bit pointers, quintptr is a typedef for quint32; on a system with 64-bit pointers, quintptr is a typedef for quint64. Note that qptrdiff is signed. Use quintptr for unsigned values. See also quintptr, qint32, and qint64. typedef qreal Typedef for double unless Qt is configured with the -qreal float option. typedef quint8 Typedef for unsigned char. This type is guaranteed to be 8-bit on all platforms supported by Qt. typedef quint16 Typedef for unsigned short. This type is guaranteed to be 16-bit on all platforms supported by Qt. typedef quint32 Typedef for unsigned 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 this type can be created using the Q_UINT64_C() macro: quint64 value = Q_UINT64_C(932838457459459); See also Q_UINT64_C(), qint64, and qulonglong. typedef quintptr Integral type for representing pointers in an unsigned integer (useful for hashing, etc.). Typedef for either quint32 or quint64. This type is guaranteed to be the same size as a pointer on all platforms supported by Qt. On a system with 32-bit pointers, quintptr is a typedef for quint32; on a system with 64-bit pointers, quintptr is a typedef for quint64. Note that quintptr is unsigned. Use qptrdiff for signed values. See also qptrdiff, quint32, and quint64. typedef qulonglong Typedef for unsigned long long int (unsigned __int64 on Windows). This is the same as quint64. See also quint64 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) Compares value to the 0 of type T and returns the absolute value. Thus if T is double, then value is compared to (double) 0. Example: int absoluteValue; int myValue = -4; absoluteValue = qAbs(myValue); // absoluteValue == 4 QtPrivat8b7c:f320:99b9:690f:4595:cd17:293a:c069QAddConst<T>8b7c:f320:99b9:690f:4595:cd17:293a:c069Type &qAsConst(T &t) Returns t cast to const T. This function is a Qt implementation of C++17's st8b7c:f320:99b9:690f:4595:cd17:293a:c069as_const(), a cast function like st8b7c:f320:99b9:690f:4595:cd17:293a:c069move(). But while st8b7c:f320:99b9:690f:4595:cd17:293a:c069move() turns lvalues into rvalues, this function turns non-const lvalues into const lvalues. Like st8b7c:f320:99b9:690f:4595:cd17:293a:c069as_const(), it doesn't work on rvalues, because it cannot be efficiently implemented for rvalues without leaving dangling references. Its main use in Qt is to prevent implicitly-shared Qt containers from detaching: QString s = ...; for (QChar ch : s) // detaches 's' (performs a deep-copy if 's' was shared) process(ch); for (QChar ch : qAsConst(s)) // ok, no detach attempt process(ch); Of course, in this case, you could (and probably should) have declared s as const in the first place: const QString s = ...; for (QChar ch : s) // ok, no detach attempt on const objects process(ch); but often that is not easily possible. It is important to note that qAsConst() does not copy its argument, it just performs a const_cast<const T&>(t). This is also the reason why it is designed to fail for rvalues: The returned reference would go stale too soon. So while this works (but detaches the returned object): for (QChar ch : funcReturningQString()) process(ch); // OK, the returned object is kept alive for the loop's duration this would not: for (QChar ch : qAsConst(funcReturningQString())) process(ch); // ERROR: ch is copied from deleted memory To prevent this construct from compiling (and failing at runtime), qAsConst() has a second, deleted, overload which binds to rvalues. This function was introduced in Qt 5.7. 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)). Example: int myValue = 10; int minValue = 2; int maxValue = 6; int boundedValue = qBound(minValue, myValue, maxValue); // boundedValue == 6 See also qMin() and qMax(). auto qConstOverload(T memberFunctionPointer) Returns the memberFunctionPointer pointer to a constant member function: struct Foo { void overloadedFunction(int, QString); void overloadedFunction(int, QString) const; }; ... qConstOverload<int, QString>(&Foo8b7c:f320:99b9:690f:4595:cd17:293a:c069overloadedFunction) ... qNonConstOverload<int, QString>(&Foo8b7c:f320:99b9:690f:4595:cd17:293a:c069overloadedFunction) This function was introduced in Qt 5.7. See also qOverload, qNonConstOverload, and Differences between String-Based and Functor-Based Connections. int qEnvironmentVariableIntValue(const char *varName, bool *ok = Q_NULLPTR) Returns the numerical value of the environment variable varName. If ok is not null, sets *ok to true or false depending on the success of the conversion. Equivalent to qgetenv(varName).toInt(ok, 0) except that it's much faster, and can't throw exceptions. Note: there's a limit on the length of the value, which is sufficient for all valid values of int, not counting leading zeroes or spaces. Values that are too long will either be truncated or this function will set ok to false. This function was introduced in Qt 5.5. See also qgetenv() and qEnvironmentVariableIsSet(). bool qEnvironmentVariableIsEmpty(const char *varName) Returns whether the environment variable varName is empty. Equivalent to qgetenv(varName).isEmpty() except that it's potentially much faster, and can't throw exceptions. This function was introduced in Qt 5.1. See also qgetenv() and qEnvironmentVariableIsSet(). bool qEnvironmentVariableIsSet(const char *varName) Returns whether the environment variable varName is set. Equivalent to !qgetenv(varName).isNull() except that it's potentially much faster, and can't throw exceptions. This function was introduced in Qt 5.1. See also qgetenv() and qEnvironmentVariableIsEmpty(). quint32 qFloatDistance(float a, float b) Returns the number of representable floating-point numbers between a and b. This function provides an alternative way of doing approximated comparisons of floating-point numbers similar to qFuzzyCompare(). However, it returns the distance between two numbers, which gives the caller a possibility to choose the accepted error. Errors are relative, so for instance the distance between 1.0E-5 and 1.00001E-5 will give 110, while the distance between 1.0E36 and 1.00001E36 will give 127. This function is useful if a floating point comparison requires a certain precision. Therefore, if a and b are equal it will return 0. The maximum value it will return for 32-bit floating point numbers is 4,278,190,078. This is the distance between -FLT_MAX and +FLT_MAX. The function does not give meaningful results if any of the arguments are Infinite or NaN. You can check for this by calling qIsFinite(). The return value can be considered as the "error", so if you for instance want to compare two 32-bit floating point numbers and all you need is an approximated 24-bit precision, you can use this function like this: if (qFloatDistance(a, b) < (1 << 7)) { // The last 7 bits are not // significant // precise enough } This function was introduced in Qt 5.2. See also qFuzzyCompare(). quint64 qFloatDistance(double a, double b) Returns the number of representable floating-point numbers between a and b. This function serves the same purpose as qFloatDistance(float, float), but returns the distance between two double numbers. Since the range is larger than for two float numbers ([-DBL_MAX,DBL_MAX]), the return type is quint64. This function was introduced in Qt 5.2. See also qFuzzyCompare(). QString qFormatLogMessage(QtMsgType type, const QMessageLogContext &context, const QString &str) Generates a formatted string out of the type, context, str arguments. qFormatLogMessage returns a QString that is formatted according to the current message pattern. It can be used by custom message handlers to format output similar to Qt's default message handler. The function is thread-safe. This function was introduced in Qt 5.4. See also qInstallMessageHandler() and qSetMessagePattern(). [static] bool qFuzzyCompare(double p1, double p2) 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, nor does comparing values where one of the values is NaN or infinity. If one of the values is always 0.0, use qFuzzyIsNull instead. If one of the values is likely to be 0.0, one solution is to add 1.0 to both values. // 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. [static] bool qFuzzyCompare(float p1, float p2) 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. [static] bool qFuzzyIsNull(double d) Returns true if the absolute value of d is within 0.000000000001 of 0.0. Note: This function is thread-safe. This function was introduced in Qt 4.4. [static] bool qFuzzyIsNull(float f) Returns true if the absolute value of f is within 0.00001f of 0.0. Note: This function is thread-safe. This function was introduced in Qt 4.4. double qInf() Returns the bit pattern for an infinite number as a double. QtMessageHandler qInstallMessageHandler(QtMessageHandler handler) Installs a Qt message handler which has been defined previously. Returns a pointer to the previous message handler. The message handler is a function that prints out debug messages, warnings, critical and fatal error messages. The Qt library (debug mode) contains hundreds of warning messages that are printed when internal errors (usually invalid function arguments) occur. Qt built in release mode also contains such warnings unless QT_NO_WARNING_OUTPUT and/or QT_NO_DEBUG_OUTPUT have been set during compilation. 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 qInstallMessageHandler(0). Example: #include <qapplication.h> #include <stdio.h> #include <stdlib.h> void myMessageOutput(QtMsgType type, const QMessageLogContext &context, const QString &msg) { QByteArray localMsg = msg.toLocal8Bit(); switch (type) { case QtDebugMsg: fprintf(stderr, "Debug: %s (%s:%u, %s)\n", localMsg.constData(), context.file, context.line, context.function); break; case QtInfoMsg: fprintf(stderr, "Info: %s (%s:%u, %s)\n", localMsg.constData(), context.file, context.line, context.function); break; case QtWarningMsg: fprintf(stderr, "Warning: %s (%s:%u, %s)\n", localMsg.constData(), context.file, context.line, context.function); break; case QtCriticalMsg: fprintf(stderr, "Critical: %s (%s:%u, %s)\n", localMsg.constData(), context.file, context.line, context.function); break; case QtFatalMsg: fprintf(stderr, "Fatal: %s (%s:%u, %s)\n", localMsg.constData(), context.file, context.line, context.function); abort(); } } int main(int argc, char **argv) { qInstallMessageHandler(myMessageOutput); QApplication app(argc, argv); ... return app.exec(); } This function was introduced in Qt 5.0. See also QtMessageHandler, QtMsgType, qDebug(), qInfo(), qWarning(), qCritical(), qFatal(), and Debugging Techniques. bool qIsFinite(double d) Returns true if the double d is a finite number. bool qIsFinite(float f) Returns true if the float f is a finite number. bool qIsInf(double d) Returns true if the double d is equivalent to infinity. bool qIsInf(float f) Returns true if the float f is equivalent to infinity. bool qIsNaN(double d) Returns true if the double d is not a number (NaN). bool qIsNaN(float f) Returns true if the float f is not a number (NaN). const T &qMax(const T &value1, const T &value2) Returns the maximum of value1 and value2. Example: int myValue = 6; int yourValue = 4; int maxValue = qMax(myValue, yourValue); // maxValue == myValue See also qMin() and qBound(). const T &qMin(const T &value1, const T &value2) Returns the minimum of value1 and value2. Example: int myValue = 6; int yourValue = 4; int minValue = qMin(myValue, yourValue); // minValue == yourValue See also qMax() and qBound(). auto qNonConstOverload(T memberFunctionPointer) Returns the memberFunctionPointer pointer to a non-constant member function: struct Foo { void overloadedFunction(int, QString); void overloadedFunction(int, QString) const; }; ... qConstOverload<int, QString>(&Foo8b7c:f320:99b9:690f:4595:cd17:293a:c069overloadedFunction) ... qNonConstOverload<int, QString>(&Foo8b7c:f320:99b9:690f:4595:cd17:293a:c069overloadedFunction) This function was introduced in Qt 5.7. See also qOverload, qNonConstOverload, and Differences between String-Based and Functor-Based Connections. auto qOverload(T functionPointer) Returns a pointer to an overloaded function. The template parameter is the list of the argument types of the function. functionPointer is the pointer to the (member) function: struct Foo { void overloadedFunction(); void overloadedFunction(int, QString); }; ... qOverload<>(&Foo8b7c:f320:99b9:690f:4595:cd17:293a:c069overloadedFunction) ... qOverload<int, QString>(&Foo8b7c:f320:99b9:690f:4595:cd17:293a:c069overloadedFunction) If a member function is also const-overloaded qConstOverload and qNonConstOverload need to be used. qOverload() requires C++14 enabled. In C++11-only code, the helper classes QOverload, QConstOverload, and QNonConstOverload can be used directly: ... QOverload<>8b7c:f320:99b9:690f:4595:cd17:293a:c069of(&Foo8b7c:f320:99b9:690f:4595:cd17:293a:c069overloadedFunction) ... QOverload<int, QString>8b7c:f320:99b9:690f:4595:cd17:293a:c069of(&Foo8b7c:f320:99b9:690f:4595:cd17:293a:c069overloadedFunction) This function was introduced in Qt 5.7. See also qConstOverload(), qNonConstOverload(), and Differences between String-Based and Functor-Based Connections. double qQNaN() Returns the bit pattern of a quiet NaN as a double. qint64 qRound64(double value) Rounds value to the nearest 64-bit integer. Example: double valueA = 42949672960.3; double valueB = 42949672960.7; qint64 roundedValueA = qRound64(valueA); // roundedValueA = 42949672960 qint64 roundedValueB = qRound64(valueB); // roundedValueB = 42949672961 qint64 qRound64(float value) Rounds value to the nearest 64-bit integer. Example: float valueA = 42949672960.3; float valueB = 42949672960.7; qint64 roundedValueA = qRound64(valueA); // roundedValueA = 42949672960 qint64 roundedValueB = qRound64(valueB); // roundedValueB = 42949672961 int qRound(double value) Rounds value to the nearest integer. Example: double valueA = 2.3; double valueB = 2.7; int roundedValueA = qRound(valueA); // roundedValueA = 2 int roundedValueB = qRound(valueB); // roundedValueB = 3 int qRound(float value) Rounds value to the nearest integer. Example: float valueA = 2.3; float valueB = 2.7; int roundedValueA = qRound(valueA); // roundedValueA = 2 int roundedValueB = qRound(valueB); // roundedValueB = 3 double qSNaN() Returns the bit pattern of a signalling NaN as a double. void qSetMessagePattern(const QString &pattern) Changes the output of the default message handler. Allows to tweak the output of qDebug(), qInfo(), qWarning(), qCritical(), and qFatal(). The category logging output of qCDebug(), qCInfo(), qCWarning(), and qCCritical() is formatted, too. Following placeholders are supported: Placeholder Description %{appname} QCoreApplication8b7c:f320:99b9:690f:4595:cd17:293a:c069pplicationName() %{category} Logging category %{file} Path to source file %{function} Function %{line} Line in source file %{message} The actual message %{pid} QCoreApplication8b7c:f320:99b9:690f:4595:cd17:293a:c069pplicationPid() %{threadid} The system-wide ID of current thread (if it can be obtained) %{qthreadptr} A pointer to the current QThread (result of QThr8b7c:f320:99b9:690f:4595:cd17:293a:c069currentThread()) %{type} "debug", "warning", "critical" or "fatal" %{time process} time of the message, in seconds since the process started (the token "process" is literal) %{time boot} the time of the message, in seconds since the system boot if that can be determined (the token "boot" is literal). If the time since boot could not be obtained, the output is indeterminate (see QElapsedTimer8b7c:f320:99b9:690f:4595:cd17:293a:c069msecsSinceReference()). %{time [format]} system time when the message occurred, formatted by passing the format to QDateTim8b7c:f320:99b9:690f:4595:cd17:293a:c069toString(). If the format is not specified, the format of Qt8b7c:f320:99b9:690f:4595:cd17:293a:c069ISODate is used. %{backtrace [depth=N] [separator="..."]} A backtrace with the number of frames specified by the optional depth parameter (defaults to 5), and separated by the optional separator parameter (defaults to "|"). This expansion is available only on some platforms (currently only platfoms using glibc). Names are only known for exported functions. If you want to see the name of every function in your application, use QMAKE_LFLAGS += -rdynamic. When reading backtraces, take into account that frames might be missing due to inlining or tail call optimization. You can also use conditionals on the type of the message using %{if-debug}, %{if-info} %{if-warning}, %{if-critical} or %{if-fatal} followed by an %{endif}. What is inside the %{if-*} and %{endif} will only be printed if the type matches. Finally, text inside %{if-category} ... %{endif} is only printed if the category is not the default one. Example: QT_MESSAGE_PATTERN="[%{time yyyyMMdd h:mm:ss.zzz t} %{if-debug}D%{endif}%{if-info}I%{endif}%{if-warning}W%{endif}%{if-critical}C%{endif}%{if-fatal}F%{endif}] %{file}:%{line} - %{message}" The default pattern is "%{if-category}%{category}: %{endif}%{message}". The pattern can also be changed at runtime by setting the QT_MESSAGE_PATTERN environment variable; if both qSetMessagePattern() is called and QT_MESSAGE_PATTERN is set, the environment variable takes precedence. Custom message handlers can use qFormatLogMessage() to take pattern into account. This function was introduced in Qt 5.0. See also qInstallMessageHandler(), Debugging Techniques, and QLoggingCategory. T *q_check_ptr(T *pointer) Uses Q_CHECK_PTR on pointer, then returns pointer. This can be used as an inline version of Q_CHECK_PTR. QByteArray qgetenv(const char *varName) Returns the value of the environment variable with name varName. To get the variable string, use QByteArray8b7c:f320:99b9:690f:4595:cd17:293a:c069onstData(). To convert the data to a QString use QString8b7c:f320:99b9:690f:4595:cd17:293a:c069romLocal8Bit(). Note: qgetenv() was introduced because getenv() from the standard C library was deprecated in VC2005 (and later versions). qgetenv() uses the new replacement function in VC, and calls the standard C library's implementation on all other platforms. Warning: Don't use qgetenv on Windows if the content may contain non-US-ASCII characters, like file paths. See also qputenv(), qEnvironmentVariableIsSet(), and qEnvironmentVariableIsEmpty(). bool qputenv(const char *varName, const QByteArray &value) This function sets the value of the environment variable named varName. It will create the variable if it does not exist. It returns 0 if the variable could not be set. Calling qputenv with an empty value removes the environment variable on Windows, and makes it set (but empty) on Unix. Prefer using qunsetenv() for fully portable behavior. Note: qputenv() was introduced because putenv() from the standard C library was deprecated in VC2005 (and later versions). qputenv() uses the replacement function in VC, and calls the standard C library's implementation on all other platforms. See also qgetenv(). int qrand() Thread-safe version of the standard C++ rand() function. Returns a value between 0 and RAND_MAX (defined in <cstdlib> and <stdlib.h>), the next number in the current sequence of pseudo-random integers. Use qsrand() to initialize the pseudo-random number generator with a seed value. This function was introduced in Qt 4.2. See also qsrand(). void qsrand(uint seed) Thread-safe version of the standard C++ srand() function. Sets the argument seed to be used to generate a new random number sequence of pseudo random integers to be returned by qrand(). The sequence of random numbers generated is deterministic per thread. For example, if two threads call qsrand(1) and subsequently call qrand(), the threads will get the same random number sequence. This function was introduced in Qt 4.2. See also qrand(). QString qtTrId(const char *id, int n = -1) The qtTrId function finds and returns a translated string. Returns a translated string identified by id. If no matching string is found, the id itself is returned. This should not happen under normal conditions. If n >= 0, all occurrences of %n in the resulting string are replaced with a decimal representation of n. In addition, depending on n's value, the translation text may vary. Meta data and comments can be passed as documented for QObject8b7c:f320:99b9:690f:4595:cd17:293a:c069tr(). In addition, it is possible to supply a source string template like that: //% <C string> or \begincomment% <C string> \endcomment Example: //% "%n fooish bar(s) found.\n" //% "Do you want to continue?" QString text = qtTrId("qtn_foo_bar", n); Creating QM files suitable for use with this function requires passing the -idbased option to the lrelease tool. Warning: This method is reentrant only if all translators are installed before calling this method. Installing or removing translators while performing translations is not supported. Doing so will probably result in crashes or other undesirable behavior. Note: This function is reentrant. This function was introduced in Qt 4.6. See also QObject8b7c:f320:99b9:690f:4595:cd17:293a:c069tr(), QCoreApplication8b7c:f320:99b9:690f:4595:cd17:293a:c069translate(), and Internationalization with Qt. bool qunsetenv(const char *varName) This function deletes the variable varName from the environment. Returns true on success. This function was introduced in Qt 5.1. See also qputenv() and qgetenv(). Macro Documentation QT_DEPRECATED_WARNINGS If this macro is defined, the compiler will generate warnings if API declared as deprecated by Qt is used. See also QT_DISABLE_DEPRECATED_BEFORE. QT_DISABLE_DEPRECATED_BEFORE This macro can be defined in the project file to disable functions deprecated in a specified version of Qt or any earlier version. The default version number is 5.0, meaning that functions deprecated in or before Qt 5.0 will not be included. Examples: When using a future release of Qt 5, set QT_DISABLE_DEPRECATED_BEFORE=0x050100 to disable functions deprecated in Qt 5.1 and earlier. In any release, set QT_DISABLE_DEPRECATED_BEFORE=0x000000 to enable any functions, including the ones deprecated in Qt 5.0 See also QT_DEPRECATED_WARNINGS. QT_POINTER_SIZE Expands to the size of a pointer in bytes (4 or 8). This is equivalent to sizeof(void *) but can be used in a preprocessor directive. QT_REQUIRE_VERSION(int argc, char **argv, const char *version) This macro can be used to ensure that the application is run against a recent enough version of Qt. This is especially useful if your application depends on a specific bug fix introduced in a bug-fix release (e.g., 4.0.2). The argc and argv parameters are the main() function's argc and argv parameters. The version parameter is a string literal that specifies which version of Qt the application requires (e.g., "4.0.2"). Example: #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(); } QT_TRANSLATE_NOOP3(context, sourceText, comment) Marks the string literal sourceText for dynamic translation in the given context and with comment, i.e the stored sourceText will not be altered. The context is typically a class and also needs to be specified as string literal. The string literal comment will be available for translators using e.g. Qt Linguist. The macro expands to anonymous struct of the two string literals passed as sourceText and comment. Example: 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 FriendlyConversation8b7c:f320:99b9:690f:4595:cd17:293a:c069greeting(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); } This function was introduced in Qt 4.4. See also QT_TR_NOOP(), QT_TRANSLATE_NOOP(), and Internationalization with Qt. QT_TRANSLATE_NOOP(context, sourceText) Marks the string literal sourceText for dynamic translation in the given context; i.e, the stored sourceText will not be altered. The context is typically a class and also needs to be specified as string literal. The macro expands to sourceText. Example: static const char *greeting_strings[] = { QT_TRANSLATE_NOOP("FriendlyConversation", "Hello"), QT_TRANSLATE_NOOP("FriendlyConversation", "Goodbye") }; QString FriendlyConversation8b7c:f320:99b9:690f:4595:cd17:293a:c069greeting(int type) { return tr(greeting_strings[type]); } QString global_greeting(int type) { return qApp->translate("FriendlyConversation", greeting_strings[type]); } See also QT_TR_NOOP(), QT_TRANSLATE_NOOP3(), and Internationalization with Qt. QT_TRID_NOOP(id) The QT_TRID_NOOP macro marks an id for dynamic translation. The only purpose of this macro is to provide an anchor for attaching meta data like to qtTrId(). The macro expands to id. Example: 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 TheClass8b7c:f320:99b9:690f:4595:cd17:293a:c069Labels() { for (int i = 0; ids[i]; ++i) new QLabel(qtTrId(ids[i]), this); } This function was introduced in Qt 4.6. See also qtTrId() and Internationalization with Qt. QT_TR_NOOP(sourceText) Marks the string literal sourceText for dynamic translation in the current context (class), i.e the stored sourceText will not be altered. The macro expands to sourceText. Example: QString FriendlyConversation8b7c:f320:99b9:690f:4595:cd17:293a:c069greeting(int type) { static const char *greeting_strings[] = { QT_TR_NOOP("Hello"), QT_TR_NOOP("Goodbye") }; return tr(greeting_strings[type]); } The macro QT_TR_NOOP_UTF8() is identical except that it tells lupdate that the source string is encoded in UTF-8. Corresponding variants exist in the QT_TRANSLATE_NOOP() family of macros, too. See also QT_TRANSLATE_NOOP() and Internationalization with Qt. QT_VERSION This macro expands a numeric value of the form 0xMMNNPP (MM = major, NN = minor, PP = patch) that specifies Qt's version number. For example, if you compile your application against Qt 4.1.2, the QT_VERSION macro will expand to 0x040102. You can use QT_VERSION to use the latest Qt features where available. Example: #if QT_VERSION >= 0x040100 QIcon icon = style()->standardIcon(QStyl8b7c:f320:99b9:690f:4595:cd17:293a:c069SP_TrashIcon); #else QPixmap pixmap = style()->standardPixmap(QStyl8b7c:f320:99b9:690f:4595:cd17:293a:c069SP_TrashIcon); QIcon icon(pixmap); #endif See also QT_VERSION_STR and qVersion(). QT_VERSION_CHECK Turns the major, minor and patch numbers of a version into an integer, 0xMMNNPP (MM = major, NN = minor, PP = patch). This can be compared with another similarly processed version id. Example: #include <QtGlobal> #if (QT_VERSION >= QT_VERSION_CHECK(5, 0, 0)) #include <QtWidgets> #else #include <QtGui> #endif See also QT_VERSION. QT_VERSION_STR This macro expands to a string that specifies Qt's version number (for example, "4.1.2"). This is the version against which the application is compiled. See also qVersion() and QT_VERSION. 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 7 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 7 See also Q_ASSERT(), qFatal(), and Debugging Techniques. void Q_ASSUME(bool expr) Causes the compiler to assume that expr is true. This macro is useful for improving code generation, by providing the compiler with hints about conditions that it would not otherwise know about. However, there is no guarantee that the compiler will actually use those hints. This macro could be considered a "lighter" version of Q_ASSERT(). While Q_ASSERT will abort the program's execution if the condition is false, Q_ASSUME will tell the compiler not to generate code for those conditions. Therefore, it is important that the assumptions always hold, otherwise undefined behaviour may occur. If expr is a constantly false condition, Q_ASSUME will tell the compiler that the current code execution cannot be reached. That is, Q_ASSUME(false) is equivalent to Q_UNREACHABLE(). In debug builds the condition is enforced by an assert to facilitate debugging. Note: Q_LIKELY() tells the compiler that the expression is likely, but not the only possibility. Q_ASSUME tells the compiler that it is the only possibility. This function was introduced in Qt 5.0. See also Q_ASSERT(), Q_UNREACHABLE(), and Q_LIKELY(). Q_BIG_ENDIAN This macro represents a value you can compare to the macro Q_BYTE_ORDER to determine the endian-ness of your system. In a big-endian system, the most significant byte is stored at the lowest address. The other bytes follow in decreasing order of significance. #if Q_BYTE_ORDER == Q_BIG_ENDIAN ... #endif See also Q_BYTE_ORDER and Q_LITTLE_ENDIAN. Q_BYTE_ORDER This macro can be used to determine the byte order your system uses for storing data in memory. i.e., whether your system is little-endian or big-endian. It is set by Qt to one of the macros Q_LITTLE_ENDIAN or Q_BIG_ENDIAN. You normally won't need to worry about endian-ness, but you might, for example if you need to know which byte of an integer or UTF-16 character is stored in the lowest address. Endian-ness is important in networking, where computers with different values for Q_BYTE_ORDER must pass data back and forth. Use this macro as in the following examples. #if Q_BYTE_ORDER == Q_BIG_ENDIAN ... #endif or #if Q_BYTE_ORDER == Q_LITTLE_ENDIAN ... #endif See also Q_BIG_ENDIAN and Q_LITTLE_ENDIAN. Q_CC_BOR Defined if the application is compiled using Borland/Turbo C++. Q_CC_CDS Defined if the application is compiled using Reliant C++. Q_CC_CLANG Defined if the application is compiled using Clang. Q_CC_COMEAU Defined if the application is compiled using Comeau C++. Q_CC_DEC Defined if the application is compiled using DEC C++. Q_CC_EDG Defined if the application is compiled using Edison Design Group C++. Q_CC_GHS Defined if the application is compiled using Green Hills Optimizing C++ Compilers. Q_CC_GNU Defined if the application is compiled using GNU C++. Q_CC_HIGHC Defined if the application is compiled using MetaWare High C/C++. Q_CC_HPACC Defined if the application is compiled using HP aC++. Q_CC_INTEL Defined if the application is compiled using Intel C++ for Linux, Intel C++ for Windows. Q_CC_KAI Defined if the application is compiled using KAI C++. Q_CC_MIPS Defined if the application is compiled using MIPSpro C++. Q_CC_MSVC Defined if the application is compiled using Microsoft Visual C/C++, Intel C++ for Windows. Q_CC_OC Defined if the application is compiled using CenterLine C++. Q_CC_PGI Defined if the application is compiled using Portland Group C++. Q_CC_SUN Defined if the application is compiled using Forte Developer, or Sun Studio C++. Q_CC_SYM Defined if the application is compiled using Digital Mars C/C++ (used to be Symantec C++). Q_CC_USLC Defined if the application is compiled using SCO OUDK and UDK. Q_CC_WAT Defined if the application is compiled using Watcom C++. void Q_CHECK_PTR(void *pointer) If pointer is 0, prints a message containing the source code's file name and line number, saying that the program ran out of memory and aborts program execution. It throws st8b7c:f320:99b9:690f:4595:cd17:293a:c069bad_alloc instead if exceptions are enabled. Q_CHECK_PTR does nothing if QT_NO_DEBUG and QT_NO_EXCEPTIONS were defined during compilation. Therefore you must not use Q_CHECK_PTR to check for successful memory allocations because the check will be disabled in some cases. 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_DECLARE_TYPEINFO(Type, Flags) You can use this macro to specify information about a custom type Type. With accurate type information, Qt's generic containers can choose appropriate storage methods and algorithms. Flags can be one of the following: Q_PRIMITIVE_TYPE specifies that Type is a POD (plain old data) type with no constructor or destructor, or else a type where every bit pattern is a valid object and memcpy() creates a valid independent copy of the object. Q_MOVABLE_TYPE specifies that Type has a constructor and/or a destructor but can be moved in memory using memcpy(). Note: despite the name, this has nothing to do with move constructors or C++ move semantics. Q_COMPLEX_TYPE (the default) specifies that Type has constructors and/or a destructor and that it may not be moved in memory. Example of a "primitive" type: struct Point2D { int x; int y; }; Q_DECLARE_TYPEINFO(Point2D, Q_PRIMITIVE_TYPE); An example of a non-POD "primitive" type is QUuid: Even though QUuid has constructors (and therefore isn't POD), every bit pattern still represents a valid object, and memcpy() can be used to create a valid independent copy of a QUuid object. Example of a movable 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); Q_DECL_CONSTEXPR This macro can be used to declare variable that should be constructed at compile-time, or an inline function that can be taylor25@example.com. It expands to "constexpr" if your compiler supports that C++11 keyword, or to nothing otherwise. See also Q_DECL_RELAXED_CONSTEXPR. Q_DECL_EXPORT This macro marks a symbol for shared library export (see Creating Shared Libraries). See also Q_DECL_IMPORT. Q_DECL_FINAL This macro can be used to declare an overriding virtual or a class as "final", with Java semantics. Further-derived classes can then no longer override this virtual function, or inherit from this class, respectively. It expands to "final" if your compiler supports that C++11 contextual keyword, or something non-standard if your compiler supports something close enough to the C++11 semantics, or to nothing otherwise. The macro goes at the end of the function, usually after the const, if any: // more-derived classes no longer permitted to override this: virtual void MyWidget8b7c:f320:99b9:690f:4595:cd17:293a:c069paintEvent(QPaintEvent*) Q_DECL_FINAL; For classes, it goes in front of the : in the class definition, if any: class QRect Q_DECL_FINAL { // cannot be derived from // ... }; This function was introduced in Qt 5.0. See also Q_DECL_OVERRIDE. Q_DECL_IMPORT This macro declares a symbol to be an import from a shared library (see Creating Shared Libraries). See also Q_DECL_EXPORT. Q_DECL_NOEXCEPT This macro marks a function as never throwing. If the function does nevertheless throw, the behaviour is defined: st8b7c:f320:99b9:690f:4595:cd17:293a:c069terminate() is called. The macro expands to C++11 noexcept, if available, or to nothing otherwise. If you need the operator version of C++11 noexcept, use Q_DECL_NOEXCEPT_EXPR(x). If you don't need C++11 noexcept semantics, e.g. because your function can't possibly throw, don't use this macro, use Q_DECL_NOTHROW instead. This function was introduced in Qt 5.0. See also Q_DECL_NOTHROW and Q_DECL_NOEXCEPT_EXPR(). Q_DECL_NOEXCEPT_EXPR(x) This macro marks a function as non-throwing if x is true. If the function does nevertheless throw, the behaviour is defined: st8b7c:f320:99b9:690f:4595:cd17:293a:c069terminate() is called. The macro expands to C++11 noexcept(x), if available, or to nothing otherwise. If you need the always-true version of C++11 noexcept, use Q_DECL_NOEXCEPT. If you don't need C++11 noexcept semantics, e.g. because your function can't possibly throw, don't use this macro, use Q_DECL_NOTHROW instead. This function was introduced in Qt 5.0. See also Q_DECL_NOTHROW and Q_DECL_NOEXCEPT. Q_DECL_NOTHROW This macro marks a function as never throwing, under no circumstances. If the function does nevertheless throw, the behaviour is undefined. The macro expands to either "throw()", if that has some benefit on the compiler, or to C++11 noexcept, if available, or to nothing otherwise. If you need C++11 noexcept semantics, don't use this macro, use Q_DECL_NOEXCEPT/Q_DECL_NOEXCEPT_EXPR instead. This function was introduced in Qt 5.0. See also Q_DECL_NOEXCEPT and Q_DECL_NOEXCEPT_EXPR(). Q_DECL_OVERRIDE This macro can be used to declare an overriding virtual function. Use of this markup will allow the compiler to generate an error if the overriding virtual function does not in fact override anything. It expands to "override" if your compiler supports that C++11 contextual keyword, or to nothing otherwise. The macro goes at the end of the function, usually after the const, if any: // generate error if this doesn't actually override anything: virtual void MyWidget8b7c:f320:99b9:690f:4595:cd17:293a:c069paintEvent(QPaintEvent*) Q_DECL_OVERRIDE; This function was introduced in Qt 5.0. See also Q_DECL_FINAL. Q_DECL_RELAXED_CONSTEXPR This macro can be used to declare an inline function that can be computed at compile-time according to the relaxed rules from C++14. It expands to "constexpr" if your compiler supports C++14 relaxed constant expressions, or to nothing otherwise. See also Q_DECL_CONSTEXPR. void Q_FALLTHROUGH() Can be used in switch statements at the end of case block to tell the compiler and other developers that that the lack of a break statement is intentional. This is useful since a missing break statement is often a bug, and some compilers can be configured to emit warnings when one is not found. This function was introduced in Qt 5.8. See also Q_UNREACHABLE(). Q_FOREACH(variable, container) Same as foreach(variable, container). This macro is available even when no_keywords is specified using the .pro file's CONFIG variable. Note: Since Qt 5.7, the use of this macro is discouraged. It will be removed in a future version of Qt. Please use C++11 range-for, possibly with qAsConst(), as needed. See also qAsConst(). Q_FOREVER Same as forever. This macro is available even when no_keywords is specified using the .pro file's CONFIG variable. See also foreach(). Q_FORWARD_DECLARE_CF_TYPE(type) Forward-declares a Core Foundation type. This includes the actual type and the ref type. For example, Q_FORWARD_DECLARE_CF_TYPE(CFString) declares __CFString and CFStringRef. This function was introduced in Qt 5.2. Q_FORWARD_DECLARE_MUTABLE_CF_TYPE(type) Forward-declares a mutable Core Foundation type. This includes the actual type and the ref type. For example, Q_FORWARD_DECLARE_MUTABLE_CF_TYPE(CFMutableString) declares __CFMutableString and CFMutableStringRef. This function was introduced in Qt 5.2. Q_FORWARD_DECLARE_OBJC_CLASS(classname) Forward-declares an Objective-C classname in a manner such that it can be compiled as either Objective-C or C++. This is primarily intended for use in header files that may be included by both Objective-C and C++ source files. This function was introduced in Qt 5.2. const char *Q_FUNC_INFO() Expands to a string that describe the function the macro resides in. How this string looks more specifically is compiler dependent. With GNU GCC it is typically the function signature, while with other compilers it might be the line and column number. Q_FUNC_INFO can be conveniently used with qDebug(). For example, this function: 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; } when instantiated with the integer type, will with the GCC compiler produce: const TInputType& myMin(const TInputType&, const TInputType&) [with TInputType = int] was called with value1: 3 value2: 4 If this macro is used outside a function, the behavior is undefined. qint64 Q_INT64_C(literal) Wraps the signed 64-bit integer literal in a platform-independent way. Example: qint64 value = Q_INT64_C(932838457459459); See also qint64 and Q_UINT64_C(). Q_LIKELY(expr) Hints to the compiler that the enclosed condition, expr, is likely to evaluate to true. Use of this macro can help the compiler to optimize the code. Example: // the condition inside the "if" will be successful most of the times for (int i = 1; i <= 365; i++) { if (Q_LIKELY(isWorkingDay(i))) { ... } ... } This function was introduced in Qt 4.8. See also Q_UNLIKELY(). Q_LITTLE_ENDIAN This macro represents a value you can compare to the macro Q_BYTE_ORDER to determine the endian-ness of your system. In a little-endian system, the least significant byte is stored at the lowest address. The other bytes follow in increasing order of significance. #if Q_BYTE_ORDER == Q_LITTLE_ENDIAN ... #endif See also Q_BYTE_ORDER and Q_BIG_ENDIAN. Q_OS_AIX Defined on AIX. Q_OS_ANDROID Defined on Android. Q_OS_BSD4 Defined on Any BSD 4.4 system. Q_OS_BSDI Defined on BSD/OS. Q_OS_CYGWIN Defined on Cygwin. Q_OS_DARWIN Defined on Darwin-based operating systems such as macOS, iOS, watchOS, and tvOS. Q_OS_DGUX Defined on DG/UX. Q_OS_DYNIX Defined on DYNIX/ptx. Q_OS_FREEBSD Defined on FreeBSD. Q_OS_HPUX Defined on HP-UX. Q_OS_HURD Defined on GNU Hurd. Q_OS_IOS Defined on iOS. Q_OS_IRIX Defined on SGI Irix. Q_OS_LINUX Defined on Linux. Q_OS_LYNX Defined on LynxOS. Q_OS_MAC Deprecated synonym for Q_OS_DARWIN. Do not use. Q_OS_MACOS Defined on macOS. Q_OS_NETBSD Defined on NetBSD. Q_OS_OPENBSD Defined on OpenBSD. Q_OS_OSF Defined on HP Tru64 UNIX. Q_OS_OSX Deprecated synonym for Q_OS_MACOS. Do not use. Q_OS_QNX Defined on QNX Neutrino. Q_OS_RELIANT Defined on Reliant UNIX. Q_OS_SCO Defined on SCO OpenServer 5. Q_OS_SOLARIS Defined on Sun Solaris. Q_OS_TVOS Defined on tvOS. Q_OS_ULTRIX Defined on DEC Ultrix. Q_OS_UNIX Defined on Any UNIX BSD/SYSV system. Q_OS_UNIXWARE Defined on UnixWare 7, Open UNIX 8. Q_OS_WATCHOS Defined on watchOS. Q_OS_WIN32 Defined on 32-bit and 64-bit versions of Windows. Q_OS_WIN64 Defined on 64-bit versions of Windows. Q_OS_WIN Defined on all supported versions of Windows. That is, if Q_OS_WIN32, Q_OS_WIN64, or Q_OS_WINRT is defined. Q_OS_WINRT Defined for Windows Runtime (Windows Store apps) on Windows 8, Windows RT, and Windows Phone 8. Q_PROCESSOR_X86 Defined if the application is compiled for x86 processors. Qt currently supports two x86 variants: Q_PROCESSOR_X86_32 and Q_PROCESSOR_X86_64. See also QSysInfo8b7c:f320:99b9:690f:4595:cd17:293a:c069uildCpuArchitecture(). Q_PROCESSOR_S390 Defined if the application is compiled for S/390 processors. Qt supports one optional variant of S/390: Q_PROCESSOR_S390_X. See also QSysInfo8b7c:f320:99b9:690f:4595:cd17:293a:c069uildCpuArchitecture(). Q_PROCESSOR_ALPHA Defined if the application is compiled for Alpha processors. See also QSysInfo8b7c:f320:99b9:690f:4595:cd17:293a:c069uildCpuArchitecture(). Q_PROCESSOR_ARM Defined if the application is compiled for ARM processors. Qt currently supports three optional ARM revisions: Q_PROCESSOR_ARM_V5, Q_PROCESSOR_ARM_V6, and Q_PROCESSOR_ARM_V7. See also QSysInfo8b7c:f320:99b9:690f:4595:cd17:293a:c069uildCpuArchitecture(). Q_PROCESSOR_ARM_V5 Defined if the application is compiled for ARMv5 processors. The Q_PROCESSOR_ARM macro is also defined when Q_PROCESSOR_ARM_V5 is defined. See also QSysInfo8b7c:f320:99b9:690f:4595:cd17:293a:c069uildCpuArchitecture(). Q_PROCESSOR_ARM_V6 Defined if the application is compiled for ARMv6 processors. The Q_PROCESSOR_ARM and Q_PROCESSOR_ARM_V5 macros are also defined when Q_PROCESSOR_ARM_V6 is defined. See also QSysInfo8b7c:f320:99b9:690f:4595:cd17:293a:c069uildCpuArchitecture(). Q_PROCESSOR_ARM_V7 Defined if the application is compiled for ARMv7 processors. The Q_PROCESSOR_ARM, Q_PROCESSOR_ARM_V5, and Q_PROCESSOR_ARM_V6 macros are also defined when Q_PROCESSOR_ARM_V7 is defined. See also QSysInfo8b7c:f320:99b9:690f:4595:cd17:293a:c069uildCpuArchitecture(). Q_PROCESSOR_AVR32 Defined if the application is compiled for AVR32 processors. See also QSysInfo8b7c:f320:99b9:690f:4595:cd17:293a:c069uildCpuArchitecture(). Q_PROCESSOR_BLACKFIN Defined if the application is compiled for Blackfin processors. See also QSysInfo8b7c:f320:99b9:690f:4595:cd17:293a:c069uildCpuArchitecture(). Q_PROCESSOR_IA64 Defined if the application is compiled for IA-64 processors. This includes all Itanium and Itanium 2 processors. See also QSysInfo8b7c:f320:99b9:690f:4595:cd17:293a:c069uildCpuArchitecture(). Q_PROCESSOR_MIPS Defined if the application is compiled for MIPS processors. Qt currently supports seven MIPS revisions: Q_PROCESSOR_MIPS_I, Q_PROCESSOR_MIPS_II, Q_PROCESSOR_MIPS_III, Q_PROCESSOR_MIPS_IV, Q_PROCESSOR_MIPS_V, Q_PROCESSOR_MIPS_32, and Q_PROCESSOR_MIPS_64. See also QSysInfo8b7c:f320:99b9:690f:4595:cd17:293a:c069uildCpuArchitecture(). Q_PROCESSOR_MIPS_32 Defined if the application is compiled for MIPS32 processors. The Q_PROCESSOR_MIPS, Q_PROCESSOR_MIPS_I, and Q_PROCESSOR_MIPS_II macros are also defined when Q_PROCESSOR_MIPS_32 is defined. See also QSysInfo8b7c:f320:99b9:690f:4595:cd17:293a:c069uildCpuArchitecture(). Q_PROCESSOR_MIPS_64 Defined if the application is compiled for MIPS64 processors. The Q_PROCESSOR_MIPS, Q_PROCESSOR_MIPS_I, Q_PROCESSOR_MIPS_II, Q_PROCESSOR_MIPS_III, Q_PROCESSOR_MIPS_IV, and Q_PROCESSOR_MIPS_V macros are also defined when Q_PROCESSOR_MIPS_64 is defined. See also QSysInfo8b7c:f320:99b9:690f:4595:cd17:293a:c069uildCpuArchitecture(). Q_PROCESSOR_MIPS_I Defined if the application is compiled for MIPS-I processors. The Q_PROCESSOR_MIPS macro is also defined when Q_PROCESSOR_MIPS_I is defined. See also QSysInfo8b7c:f320:99b9:690f:4595:cd17:293a:c069uildCpuArchitecture(). Q_PROCESSOR_MIPS_II Defined if the application is compiled for MIPS-II processors. The Q_PROCESSOR_MIPS and Q_PROCESSOR_MIPS_I macros are also defined when Q_PROCESSOR_MIPS_II is defined. See also QSysInfo8b7c:f320:99b9:690f:4595:cd17:293a:c069uildCpuArchitecture(). Q_PROCESSOR_MIPS_III Defined if the application is compiled for MIPS-III processors. The Q_PROCESSOR_MIPS, Q_PROCESSOR_MIPS_I, and Q_PROCESSOR_MIPS_II macros are also defined when Q_PROCESSOR_MIPS_III is defined. See also QSysInfo8b7c:f320:99b9:690f:4595:cd17:293a:c069uildCpuArchitecture(). Q_PROCESSOR_MIPS_IV Defined if the application is
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