QLibrary Class Reference

The QLibrary class loads shared libraries at runtime. More...

#include <qlibrary.h>

Inheritance diagram for QLibrary:

Public Types
enum	LoadHint { ResolveAllSymbolsHint = 0x01, ExportExternalSymbolsHint = 0x02, LoadArchiveMemberHint = 0x04, ImprovedSearchHeuristics = 0x08 }
	This enum describes the possible hints that can be used to change the way libraries are handled when they are loaded. More...

Public Functions
QString	errorString () const
	Returns a text string with the description of the last error that occurred. More...
QString	fileName () const
bool	isLoaded () const
	Returns true if the library is loaded; otherwise returns false. More...
bool	load ()
	Loads the library and returns true if the library was loaded successfully; otherwise returns false. More...
LoadHints	loadHints () const
	QLibrary (QObject *parent=0)
	Constructs a library with the given parent. More...
	QLibrary (const QString &fileName, QObject *parent=0)
	Constructs a library object with the given parent that will load the library specified by fileName. More...
	QLibrary (const QString &fileName, int verNum, QObject *parent=0)
	Constructs a library object with the given parent that will load the library specified by fileName and major version number verNum. More...
	QLibrary (const QString &fileName, const QString &version, QObject *parent=0)
	Constructs a library object with the given parent that will load the library specified by fileName and full version number version. More...
void *	resolve (const char *symbol)
	Returns the address of the exported symbol symbol. More...
void	setFileName (const QString &fileName)
void	setFileNameAndVersion (const QString &fileName, int verNum)
	Sets the fileName property and major version number to fileName and versionNumber respectively. More...
void	setFileNameAndVersion (const QString &fileName, const QString &version)
	Sets the fileName property and full version number to fileName and version respectively. More...
void	setLoadHints (LoadHints hints)
bool	unload ()
	Unloads the library and returns true if the library could be unloaded; otherwise returns false. More...
	~QLibrary ()
	Destroys the QLibrary object. More...
Public Functions inherited from QObject
bool	blockSignals (bool b)
	If block is true, signals emitted by this object are blocked (i.e., emitting a signal will not invoke anything connected to it). More...
const QObjectList &	children () const
	Returns a list of child objects. More...
bool	connect (const QObject *sender, const char *signal, const char *member, Qt::ConnectionType type=Qt::AutoConnection) const
bool	disconnect (const char *signal=0, const QObject *receiver=0, const char *member=0)
bool	disconnect (const QObject *receiver, const char *member=0)
void	dumpObjectInfo ()
	Dumps information about signal connections, etc. More...
void	dumpObjectTree ()
	Dumps a tree of children to the debug output. More...
QList< QByteArray >	dynamicPropertyNames () const
	Returns the names of all properties that were dynamically added to the object using setProperty(). More...
virtual bool	event (QEvent *)
	This virtual function receives events to an object and should return true if the event e was recognized and processed. More...
virtual bool	eventFilter (QObject *, QEvent *)
	Filters events if this object has been installed as an event filter for the watched object. More...
template<typename T >
T	findChild (const QString &aName=QString()) const
	Returns the child of this object that can be cast into type T and that is called name, or 0 if there is no such object. More...
template<typename T >
QList< T >	findChildren (const QString &aName=QString()) const
	Returns all children of this object with the given name that can be cast to type T, or an empty list if there are no such objects. More...
template<typename T >
QList< T >	findChildren (const QRegExp &re) const
bool	inherits (const char *classname) const
	Returns true if this object is an instance of a class that inherits className or a QObject subclass that inherits className; otherwise returns false. More...
void	installEventFilter (QObject *)
	Installs an event filter filterObj on this object. More...
bool	isWidgetType () const
	Returns true if the object is a widget; otherwise returns false. More...
void	killTimer (int id)
	Kills the timer with timer identifier, id. More...
virtual const QMetaObject *	metaObject () const
	Returns a pointer to the meta-object of this object. More...
void	moveToThread (QThread *thread)
	Changes the thread affinity for this object and its children. More...
QString	objectName () const
QObject *	parent () const
	Returns a pointer to the parent object. More...
QVariant	property (const char *name) const
	Returns the value of the object's name property. More...
Q_INVOKABLE	QObject (QObject *parent=0)
	Constructs an object with parent object parent. More...
void	removeEventFilter (QObject *)
	Removes an event filter object obj from this object. More...
void	setObjectName (const QString &name)
void	setParent (QObject *)
	Makes the object a child of parent. More...
bool	setProperty (const char *name, const QVariant &value)
	Sets the value of the object's name property to value. More...
void	setUserData (uint id, QObjectUserData *data)
bool	signalsBlocked () const
	Returns true if signals are blocked; otherwise returns false. More...
int	startTimer (int interval)
	Starts a timer and returns a timer identifier, or returns zero if it could not start a timer. More...
QThread *	thread () const
	Returns the thread in which the object lives. More...
QObjectUserData *	userData (uint id) const
virtual	~QObject ()
	Destroys the object, deleting all its child objects. More...

Static Public Functions
static bool	isLibrary (const QString &fileName)
	Returns true if fileName has a valid suffix for a loadable library; otherwise returns false. More...
static void *	resolve (const QString &fileName, const char *symbol)
	Loads the library fileName and returns the address of the exported symbol symbol. More...
static void *	resolve (const QString &fileName, int verNum, const char *symbol)
	Loads the library fileName with major version number verNum and returns the address of the exported symbol symbol. More...
static void *	resolve (const QString &fileName, const QString &version, const char *symbol)
	Loads the library fileName with full version number version and returns the address of the exported symbol symbol. More...
Static Public Functions inherited from QObject
static bool	connect (const QObject *sender, const char *signal, const QObject *receiver, const char *member, Qt::ConnectionType=Qt::AutoConnection)
	Creates a connection of the given type from the signal in the sender object to the method in the receiver object. More...
static bool	connect (const QObject *sender, const QMetaMethod &signal, const QObject *receiver, const QMetaMethod &method, Qt::ConnectionType type=Qt::AutoConnection)
static bool	disconnect (const QObject *sender, const char *signal, const QObject *receiver, const char *member)
	Disconnects signal in object sender from method in object receiver. More...
static bool	disconnect (const QObject *sender, const QMetaMethod &signal, const QObject *receiver, const QMetaMethod &member)
static uint	registerUserData ()
static QString	tr (const char *sourceText, const char *comment=0, int n=-1)
static QString	trUtf8 (const char *sourceText, const char *comment=0, int n=-1)

Properties
QLibraryPrivate *	d
bool	did_load
QString	fileName
	the file name of the library More...
LoadHints	loadHints
	Give the load() function some hints on how it should behave. More...

Additional Inherited Members
Public Slots inherited from QObject
void	deleteLater ()
	Schedules this object for deletion. More...
Signals inherited from QObject
void	destroyed (QObject *=0)
	This signal is emitted immediately before the object obj is destroyed, and can not be blocked. More...
Static Public Variables inherited from QObject
static const QMetaObject	staticMetaObject
	This variable stores the meta-object for the class. More...
Protected Functions inherited from QObject
virtual void	childEvent (QChildEvent *)
	This event handler can be reimplemented in a subclass to receive child events. More...
virtual void	connectNotify (const char *signal)
	This virtual function is called when something has been connected to signal in this object. More...
virtual void	customEvent (QEvent *)
	This event handler can be reimplemented in a subclass to receive custom events. More...
virtual void	disconnectNotify (const char *signal)
	This virtual function is called when something has been disconnected from signal in this object. More...
	QObject (QObjectPrivate &dd, QObject *parent=0)
int	receivers (const char *signal) const
	Returns the number of receivers connected to the signal. More...
QObject *	sender () const
	Returns a pointer to the object that sent the signal, if called in a slot activated by a signal; otherwise it returns 0. More...
int	senderSignalIndex () const
virtual void	timerEvent (QTimerEvent *)
	This event handler can be reimplemented in a subclass to receive timer events for the object. More...
Protected Variables inherited from QObject
QScopedPointer< QObjectData >	d_ptr
Static Protected Variables inherited from QObject
static const QMetaObject	staticQtMetaObject
Related Functions inherited from QObject
T	qFindChildqFindChildren (const QObject *obj, const QString &name)()
QList< T >	qFindChildrenqFindChildren (const QObject *obj, const QString &name)()
QList< T >	qFindChildrenqFindChildren (const QObject *obj, const QRegExp &regExp)()
T *	qobject_cast (QObject *object)
	QObjectList
void *	qt_find_obj_child (QObject *parent, const char *type, const QString &name)
	Returns a pointer to the object named name that inherits type and with a given parent. More...

Detailed Description

The QLibrary class loads shared libraries at runtime.

Note

This class or function is reentrant.

An instance of a QLibrary object operates on a single shared object file (which we call a "library", but is also known as a "DLL"). A QLibrary provides access to the functionality in the library in a platform independent way. You can either pass a file name in the constructor, or set it explicitly with setFileName(). When loading the library, QLibrary searches in all the system-specific library locations (e.g. LD_LIBRARY_PATH on Unix), unless the file name has an absolute path. If the file cannot be found, QLibrary tries the name with different platform-specific file suffixes, like ".so" on Unix, ".dylib" on the Mac, or ".dll" on Windows and Symbian. This makes it possible to specify shared libraries that are only identified by their basename (i.e. without their suffix), so the same code will work on different operating systems.

The most important functions are load() to dynamically load the library file, isLoaded() to check whether loading was successful, and resolve() to resolve a symbol in the library. The resolve() function implicitly tries to load the library if it has not been loaded yet. Multiple instances of QLibrary can be used to access the same physical library. Once loaded, libraries remain in memory until the application terminates. You can attempt to unload a library using unload(), but if other instances of QLibrary are using the same library, the call will fail, and unloading will only happen when every instance has called unload().

A typical use of QLibrary is to resolve an exported symbol in a library, and to call the C function that this symbol represents. This is called "explicit linking" in contrast to "implicit linking", which is done by the link step in the build process when linking an executable against a library.

Note: In Symbian resolving symbols using their names is supported only if the library is built as STDDLL. Otherwise ordinals must be used. Also, in Symbian the path of the library is ignored and system default library location is always used.

The following code snippet loads a library, resolves the symbol "mysymbol", and calls the function if everything succeeded. If something goes wrong, e.g. the library file does not exist or the symbol is not defined, the function pointer will be 0 and won't be called.

QLibrary myLib("mylib");
typedef void (*MyPrototype)();
MyPrototype myFunction = (MyPrototype) myLib.resolve("mysymbol");
if (myFunction)
    myFunction();

The symbol must be exported as a C function from the library for resolve() to work. This means that the function must be wrapped in an extern "C" block if the library is compiled with a C++ compiler. On Windows, this also requires the use of a dllexport macro; see resolve() for the details of how this is done. For convenience, there is a static resolve() function which you can use if you just want to call a function in a library without explicitly loading the library first:

typedef void (*MyPrototype)();
MyPrototype myFunction =
        (MyPrototype) QLibrary::resolve("mylib", "mysymbol");
if (myFunction)
    myFunction();

See also

QPluginLoader

Definition at line 62 of file qlibrary.h.

Enumerations

LoadHint

enum QLibrary::LoadHint

This enum describes the possible hints that can be used to change the way libraries are handled when they are loaded.

These values indicate how symbols are resolved when libraries are loaded, and are specified using the setLoadHints() function.

• ResolveAllSymbolsHint Causes all symbols in a library to be resolved when it is loaded, not simply when resolve() is called.
• ExportExternalSymbolsHint Exports unresolved and external symbols in the library so that they can be resolved in other dynamically-loaded libraries loaded later.
• LoadArchiveMemberHint Allows the file name of the library to specify a particular object file within an archive file. If this hint is given, the filename of the library consists of a path, which is a reference to an archive file, followed by a reference to the archive member.

See also

loadHints

Enumerator
ResolveAllSymbolsHint
ExportExternalSymbolsHint
LoadArchiveMemberHint
ImprovedSearchHeuristics

Definition at line 69 of file qlibrary.h.

                  {
        ResolveAllSymbolsHint = 0x01,
        ExportExternalSymbolsHint = 0x02,
        LoadArchiveMemberHint = 0x04,
        ImprovedSearchHeuristics = 0x08
    };

Constructors and Destructors

QLibrary() [1/4]

QLibrary::QLibrary ( QObject *  parent = 0 )

explicit

Constructs a library with the given parent.

Definition at line 957 of file qlibrary.cpp.

    :QObject(parent), d(0), did_load(false)
{
}

QLibrary() [2/4]

QLibrary::QLibrary ( const QString &  fileName, QObject *  parent = 0  )

explicit

Constructs a library object with the given parent that will load the library specified by fileName.

We recommend omitting the file's suffix in fileName, since QLibrary will automatically look for the file with the appropriate suffix in accordance with the platform, e.g. ".so" on Unix, ".dylib" on Mac OS X, and ".dll" on Windows. (See fileName.)

Note: In Symbian the path portion of the fileName is ignored.

Definition at line 974 of file qlibrary.cpp.

    :QObject(parent), d(0), did_load(false)
{
    setFileName(fileName);
}

QLibrary() [3/4]

QLibrary::QLibrary ( const QString &  fileName, int  verNum, QObject *  parent = 0  )

explicit

Constructs a library object with the given parent that will load the library specified by fileName and major version number verNum.

Currently, the version number is ignored on Windows and Symbian.

We recommend omitting the file's suffix in fileName, since QLibrary will automatically look for the file with the appropriate suffix in accordance with the platform, e.g. ".so" on Unix, ".dylib" on Mac OS X, and ".dll" on Windows. (See fileName.)

Note: In Symbian the path portion of the fileName is ignored.

Definition at line 993 of file qlibrary.cpp.

    :QObject(parent), d(0), did_load(false)
{
    setFileNameAndVersion(fileName, verNum);
}

QLibrary() [4/4]

QLibrary::QLibrary ( const QString &  fileName, const QString &  version, QObject *  parent = 0  )

explicit

Constructs a library object with the given parent that will load the library specified by fileName and full version number version.

Currently, the version number is ignored on Windows and Symbian.

We recommend omitting the file's suffix in fileName, since QLibrary will automatically look for the file with the appropriate suffix in accordance with the platform, e.g. ".so" on Unix, ".dylib" on Mac OS X, and ".dll" on Windows. (See fileName.)

Note: In Symbian the path portion of the fileName is ignored.

Definition at line 1011 of file qlibrary.cpp.

    :QObject(parent), d(0), did_load(false)
{
    setFileNameAndVersion(fileName, version);
}

~QLibrary()

QLibrary::~QLibrary

(

)

Destroys the QLibrary object.

Unless unload() was called explicitly, the library stays in memory until the application terminates.

See also

isLoaded(), unload()

Definition at line 1025 of file qlibrary.cpp.

{
    if (d)
        d->release();
}

Functions

errorString()

QString QLibrary::errorString

(

)

const

Returns a text string with the description of the last error that occurred.

Since

4.2

Currently, errorString will only be set if load(), unload() or resolve() for some reason fails.

Definition at line 1267 of file qlibrary.cpp.

Referenced by qt_initIcu().

{
    return (!d || d->errorString.isEmpty()) ? tr("Unknown error") : d->errorString;
}

fileName()

QString QLibrary::fileName

(

)

const

Referenced by setFileName().

isLibrary()

bool QLibrary::isLibrary ( const QString &  fileName )

static

Returns true if fileName has a valid suffix for a loadable library; otherwise returns false.

Platform	Valid suffixes
Windows	.dll, .DLL
Unix/Linux	.so
AIX	.a
HP-UX	.sl, .so (HP-UXi)
Mac OS X	.dylib, .bundle, .so
Symbian	.dll

Trailing versioning numbers on Unix are ignored.

Definition at line 559 of file qlibrary.cpp.

{
#if defined(Q_OS_WIN32) || defined(Q_OS_WINCE)
    return fileName.endsWith(QLatin1String(".dll"), Qt::CaseInsensitive);
#elif defined(Q_OS_SYMBIAN)
    // Plugin stubs are also considered libraries in Symbian.
    return (fileName.endsWith(QLatin1String(".dll")) ||
            fileName.endsWith(QLatin1String(".qtplugin")));
#else
    QString completeSuffix = QFileInfo(fileName).completeSuffix();
    if (completeSuffix.isEmpty())
        return false;
    QStringList suffixes = completeSuffix.split(QLatin1Char('.'));
# if defined(Q_OS_DARWIN)

    // On Mac, libs look like libmylib.1.0.0.dylib
    const QString lastSuffix = suffixes.at(suffixes.count() - 1);
    const QString firstSuffix = suffixes.at(0);

    bool valid = (lastSuffix == QLatin1String("dylib")
            || firstSuffix == QLatin1String("so")
            || firstSuffix == QLatin1String("bundle"));

    return valid;
# else  // Generic Unix
    QStringList validSuffixList;

#  if defined(Q_OS_HPUX)
/*
    See "HP-UX Linker and Libraries User's Guide", section "Link-time Differences between PA-RISC and IPF":
    "In PA-RISC (PA-32 and PA-64) shared libraries are suffixed with .sl. In IPF (32-bit and 64-bit),
    the shared libraries are suffixed with .so. For compatibility, the IPF linker also supports the .sl suffix."
 */
    validSuffixList << QLatin1String("sl");
#   if defined __ia64
    validSuffixList << QLatin1String("so");
#   endif
#  elif defined(Q_OS_AIX)
    validSuffixList << QLatin1String("a") << QLatin1String("so");
#  elif defined(Q_OS_UNIX)
    validSuffixList << QLatin1String("so");
#  endif

    // Examples of valid library names:
    //  libfoo.so
    //  libfoo.so.0
    //  libfoo.so.0.3
    //  libfoo-0.3.so
    //  libfoo-0.3.so.0.3.0

    int suffix;
    int suffixPos = -1;
    for (suffix = 0; suffix < validSuffixList.count() && suffixPos == -1; ++suffix)
        suffixPos = suffixes.indexOf(validSuffixList.at(suffix));

    bool valid = suffixPos != -1;
    for (int i = suffixPos + 1; i < suffixes.count() && valid; ++i)
        if (i != suffixPos)
            suffixes.at(i).toInt(&valid);
    return valid;
# endif
#endif

}

isLoaded()

bool QLibrary::isLoaded

(

)

const

Returns true if the library is loaded; otherwise returns false.

See also

load()

Definition at line 948 of file qlibrary.cpp.

Referenced by qdbus_loadLibDBus(), qt_init(), and resolve().

{
    return d && d->pHnd;
}

load()

bool QLibrary::load

(

)

Loads the library and returns true if the library was loaded successfully; otherwise returns false.

Since resolve() always calls this function before resolving any symbols it is not necessary to call it explicitly. In some situations you might want the library loaded in advance, in which case you would use this function.

See also

unload()

Definition at line 909 of file qlibrary.cpp.

Referenced by QApplicationPrivate::construct(), QSslSocketPrivate::ensureCiphersAndCertsLoaded(), loadOpenSslWin32(), qdbus_loadLibDBus(), qt_init(), qt_initIcu(), resolve(), resolveCups(), and resolveLibrary().

{
    if (!d)
        return false;
    if (did_load)
        return d->pHnd;
    did_load = true;
    return d->load();
}

loadHints()

LoadHints QLibrary::loadHints

(

)

const

Referenced by setLoadHints().

resolve() [1/4]

void * QLibrary::resolve

(

const char *

symbol

)

Returns the address of the exported symbol symbol.

The library is loaded if necessary. The function returns 0 if the symbol could not be resolved or if the library could not be loaded.

Example:

typedef int (*AvgFunction)(int, int);

AvgFunction avg = (AvgFunction) library->resolve("avg");
if (avg)
    return avg(5, 8);
else
    return -1;

The symbol must be exported as a C function from the library. This means that the function must be wrapped in an extern "C" if the library is compiled with a C++ compiler. On Windows you must also explicitly export the function from the DLL using the __declspec(dllexport) compiler directive, for example:

extern "C" MY_EXPORT int avg(int a, int b)
{
    return (a + b) / 2;
}

with MY_EXPORT defined as

#ifdef Q_WS_WIN
#define MY_EXPORT __declspec(dllexport)
#else
#define MY_EXPORT
#endif

Note: In Symbian resolving with symbol names works only if the loaded library was built as STDDLL. Otherwise, the ordinals must be used.

Definition at line 1155 of file qlibrary.cpp.

Referenced by QMacPasteboardMimeHTMLText::convertFromMime(), QSslSocketPrivate::ensureCiphersAndCertsLoaded(), QGtkStylePrivate::getIconThemeName(), QGLXContext::getProcAddress(), getTransformationFunction(), HB_Library_Resolve(), qdbus_loadLibDBus(), qdbus_resolve_conditionally(), qdbus_resolve_me(), qgl_use_font(), qglx_getProcAddress(), QGLXContext::QGLXContext(), QIconvCodec::QIconvCodec(), QMacStylePrivate::QMacStylePrivate(), qt_init(), qt_initIcu(), qt_load_library_runtime(), qt_retrieveNisPrinters(), resolve(), resolveAygLibs(), resolveCups(), resolveGConf(), QGtkStylePrivate::resolveGtk(), resolveLibrary(), and resolveOpenGLSymbols().

{
    if (!isLoaded() && !load())
        return 0;
    return d->resolve(symbol);
}

resolve() [2/4]

void * QLibrary::resolve ( const QString &  fileName, const char *  symbol  )

static

Loads the library fileName and returns the address of the exported symbol symbol.

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Note that fileName should not include the platform-specific file suffix; (see fileName). The library remains loaded until the application exits.

The function returns 0 if the symbol could not be resolved or if the library could not be loaded.

Note: In Symbian resolving with symbol names works only if the loaded library was built as STDDLL. Otherwise, the ordinals must be used.

See also

resolve()

Definition at line 1181 of file qlibrary.cpp.

{
    QLibrary library(fileName);
    return library.resolve(symbol);
}

resolve() [3/4]

void * QLibrary::resolve ( const QString &  fileName, int  verNum, const char *  symbol  )

static

Loads the library fileName with major version number verNum and returns the address of the exported symbol symbol.

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Note that fileName should not include the platform-specific file suffix; (see fileName). The library remains loaded until the application exits. verNum is ignored on Windows.

The function returns 0 if the symbol could not be resolved or if the library could not be loaded.

Note: In Symbian resolving with symbol names works only if the loaded library was built as STDDLL. Otherwise, the ordinals must be used.

See also

resolve()

Definition at line 1207 of file qlibrary.cpp.

{
    QLibrary library(fileName, verNum);
    return library.resolve(symbol);
}

resolve() [4/4]

void * QLibrary::resolve ( const QString &  fileName, const QString &  version, const char *  symbol  )

static

Loads the library fileName with full version number version and returns the address of the exported symbol symbol.

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Since

4.4

Note that fileName should not include the platform-specific file suffix; (see fileName). The library remains loaded until the application exits. version is ignored on Windows.

The function returns 0 if the symbol could not be resolved or if the library could not be loaded.

Note: In Symbian resolving with symbol names works only if the loaded library was built as STDDLL. Otherwise, the ordinals must be used.

See also

resolve()

Definition at line 1234 of file qlibrary.cpp.

{
    QLibrary library(fileName, version);
    return library.resolve(symbol);
}

setFileName()

void QLibrary::setFileName

(

const QString &

fileName

)

Definition at line 1058 of file qlibrary.cpp.

Referenced by qdbus_loadLibDBus(), QLibrary(), and qt_init().

{
    QLibrary::LoadHints lh;
    if (d) {
        lh = d->loadHints;
        d->release();
        d = 0;
        did_load = false;
    }
    d = QLibraryPrivate::findOrCreate(fileName);
    d->loadHints = lh;
}

setFileNameAndVersion() [1/2]

void QLibrary::setFileNameAndVersion	(	const QString &	fileName,
		int	versionNumber
	)

Sets the fileName property and major version number to fileName and versionNumber respectively.

The versionNumber is ignored on Windows and Symbian.

Note: In Symbian the path portion of the fileName is ignored.

See also

setFileName()

Definition at line 1092 of file qlibrary.cpp.

Referenced by loadOpenSslWin32(), qdbus_loadLibDBus(), and QLibrary().

{
    QLibrary::LoadHints lh;
    if (d) {
        lh = d->loadHints;
        d->release();
        d = 0;
        did_load = false;
    }
    d = QLibraryPrivate::findOrCreate(fileName, verNum >= 0 ? QString::number(verNum) : QString());
    d->loadHints = lh;
}

setFileNameAndVersion() [2/2]

void QLibrary::setFileNameAndVersion	(	const QString &	fileName,
		const QString &	version
	)

Sets the fileName property and full version number to fileName and version respectively.

Since

4.4

The version parameter is ignored on Windows and Symbian.

Note: In Symbian the path portion of the fileName is ignored.

See also

setFileName()

Definition at line 1119 of file qlibrary.cpp.

{
    QLibrary::LoadHints lh;
    if (d) {
        lh = d->loadHints;
        d->release();
        d = 0;
        did_load = false;
    }
    d = QLibraryPrivate::findOrCreate(fileName, version);
    d->loadHints = lh;
}

setLoadHints()

void QLibrary::setLoadHints

(

LoadHints

hints

)

Definition at line 1304 of file qlibrary.cpp.

Referenced by QGtkStylePrivate::getIconThemeName(), loadOpenSslWin32(), qdbus_loadLibDBus(), qgl_use_font(), qglx_getProcAddress(), QIconvCodec::QIconvCodec(), QMacStylePrivate::QMacStylePrivate(), qt_init(), qt_initIcu(), qt_load_library_runtime(), QGtkStylePrivate::resolveGtk(), and resolveLibrary().

{
    if (!d) {
        d = QLibraryPrivate::findOrCreate(QString());   // ugly, but we need a d-ptr
        d->errorString.clear();
    }
    d->loadHints = hints;
}

unload()

bool QLibrary::unload

(

)

Unloads the library and returns true if the library could be unloaded; otherwise returns false.

This happens automatically on application termination, so you shouldn't normally need to call this function.

If other instances of QLibrary are using the same library, the call will fail, and unloading will only happen when every instance has called unload().

Note that on Mac OS X 10.3 (Panther), dynamic libraries cannot be unloaded.

See also

resolve(), load()

Definition at line 934 of file qlibrary.cpp.

Referenced by loadOpenSslWin32(), and qdbus_loadLibDBus().

{
    if (did_load) {
        did_load = false;
        return d->unload();
    }
    return false;
}

Properties

d

QLibraryPrivate* QLibrary::d

private

Definition at line 108 of file qlibrary.h.

Referenced by errorString(), resolve(), setFileName(), setFileNameAndVersion(), setLoadHints(), and ~QLibrary().

did_load

bool QLibrary::did_load

private

Definition at line 109 of file qlibrary.h.

Referenced by setFileName(), and setFileNameAndVersion().

fileName

QString QLibrary::fileName

private

the file name of the library

We recommend omitting the file's suffix in the file name, since QLibrary will automatically look for the file with the appropriate suffix (see isLibrary()).

When loading the library, QLibrary searches in all system-specific library locations (e.g. LD_LIBRARY_PATH on Unix), unless the file name has an absolute path. After loading the library successfully, fileName() returns the fully-qualified file name of the library, including the full path to the library if one was given in the constructor or passed to setFileName().

For example, after successfully loading the "GL" library on Unix platforms, fileName() will return "libGL.so". If the file name was originally passed as "/usr/lib/libGL", fileName() will return "/usr/lib/libGL.so".

Note: In Symbian the path portion of the fileName is ignored.

Definition at line 65 of file qlibrary.h.

Referenced by qdbus_loadLibDBus().

loadHints

QLibrary::LoadHints QLibrary::loadHints

private

Give the load() function some hints on how it should behave.

You can give some hints on how the symbols are resolved. Usually, the symbols are not resolved at load time, but resolved lazily, (that is, when resolve() is called). If you set the loadHint to ResolveAllSymbolsHint, then all symbols will be resolved at load time if the platform supports it.

Setting ExportExternalSymbolsHint will make the external symbols in the library available for resolution in subsequent loaded libraries.

If LoadArchiveMemberHint is set, the file name is composed of two components: A path which is a reference to an archive file followed by the second component which is the reference to the archive member. For instance, the fileName libGL.a(shr_64.o) will refer to the library shr_64.o in the archive file named libGL.a. This is only supported on the AIX platform.

The interpretation of the load hints is platform dependent, and if you use it you are probably making some assumptions on which platform you are compiling for, so use them only if you understand the consequences of them.

By default, none of these flags are set, so libraries will be loaded with lazy symbol resolution, and will not export external symbols for resolution in other dynamically-loaded libraries.

Definition at line 66 of file qlibrary.h.

Referenced by loadOpenSslWin32().

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The documentation for this class was generated from the following files:

• /src/corelib/plugin/qlibrary.h
• /src/corelib/plugin/qlibrary.cpp