qlibrary.cpp

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**
** Copyright (C) 2020 The Qt Company Ltd.
** Copyright (C) 2021 Intel Corporation.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the QtCore module of the Qt Toolkit.
**
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** packaging of this file. Please review the following information to
** ensure the GNU Lesser General Public License version 3 requirements
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****************************************************************************/
#include "qlibrary.h"
#include "qlibrary_p.h"
 
#include <q20algorithm.h>
#include <qbytearraymatcher.h>
#include <qdebug.h>
#include <qendian.h>
#include <qfile.h>
#include <qfileinfo.h>
#include <qjsondocument.h>
#include <qmap.h>
#include <qmutex.h>
#include <qoperatingsystemversion.h>
#include <qstringlist.h>
 
#ifdef Q_OS_MAC
#  include <private/qcore_mac_p.h>
#endif
#include <private/qcoreapplication_p.h>
#include <private/qloggingregistry_p.h>
#include <private/qsystemerror_p.h>
 
#include "qcoffpeparser_p.h"
#include "qelfparser_p.h"
#include "qfactoryloader_p.h"
#include "qmachparser_p.h"
 
#include <qtcore_tracepoints_p.h>
 
QT_BEGIN_NAMESPACE
 
// On Unix systema and on Windows with MinGW, we can mix and match debug and
// release plugins without problems. (unless compiled in debug-and-release mode
// - why?)
static constexpr bool PluginMustMatchQtDebug =
        QOperatingSystemVersion::currentType() == QOperatingSystemVersion::Windows
#if defined(Q_CC_MINGW)
        && QT_CONFIG(debug_and_release)
#endif
        ;
 
#ifdef QT_NO_DEBUG
static constexpr bool QtBuildIsDebug = false;
#else
static constexpr bool QtBuildIsDebug = true;
#endif
 
Q_LOGGING_CATEGORY_WITH_ENV_OVERRIDE(qt_lcDebugPlugins, "QT_DEBUG_PLUGINS", "qt.core.plugin.loader")
static Q_LOGGING_CATEGORY_WITH_ENV_OVERRIDE(lcDebugLibrary, "QT_DEBUG_PLUGINS", "qt.core.library")
 
static QLibraryScanResult qt_find_pattern(const char *s, qsizetype s_len, QString *errMsg)
{
    /*
      We used to search from the end of the file so we'd skip the code and find
      the read-only data that usually follows. Unfortunately, in debug builds,
      the debug sections come after and are usually much bigger than everything
      else, making this process slower than necessary with debug plugins.
 
      More importantly, the pattern string may exist in the debug information due
      to it being used in the plugin in the first place.
    */
#if defined(Q_OF_ELF)
    return QElfParser::parse({s, s_len}, errMsg);
#elif defined(Q_OF_MACH_O)
    return QMachOParser::parse(s, s_len, errMsg);
#elif defined(Q_OS_WIN)
    return QCoffPeParser::parse({s, s_len}, errMsg);
#endif
    static constexpr auto matcher = [] {
        // QPluginMetaData::MagicString is not NUL-terminated, but
        // qMakeStaticByteArrayMatcher requires its argument to be, so
        // duplicate here, but statically check we didn't mess up:
        constexpr auto &pattern = "QTMETADATA !";
        constexpr auto magic = std::string_view(QPluginMetaData::MagicString,
                                                sizeof(QPluginMetaData::MagicString));
        static_assert(pattern == magic);
        return qMakeStaticByteArrayMatcher(pattern);
    }();
    qsizetype i = matcher.indexIn(s, s_len);
    if (i < 0) {
        *errMsg = QLibrary::tr("'%1' is not a Qt plugin").arg(*errMsg);
        return QLibraryScanResult{};
    }
    i += sizeof(QPluginMetaData::MagicString);
    return { i, s_len - i };
}
 
/*
  This opens the specified library, mmaps it into memory, and searches
  for the QT_PLUGIN_VERIFICATION_DATA.  The advantage of this approach is that
  we can get the verification data without have to actually load the library.
  This lets us detect mismatches more safely.
 
  Returns \c false if version information is not present, or if the
                information could not be read.
  Returns  true if version information is present and successfully read.
*/
static bool findPatternUnloaded(const QString &library, QLibraryPrivate *lib)
{
    QFile file(library);
    if (!file.open(QIODevice::ReadOnly)) {
        if (lib)
            lib->errorString = file.errorString();
        qCWarning(qt_lcDebugPlugins, "%ls: cannot open: %ls", qUtf16Printable(library),
                  qUtf16Printable(file.errorString()));
        return false;
    }
 
    // Files can be bigger than the virtual memory size on 32-bit systems, so
    // we limit to 512 MB there. For 64-bit, we allow up to 2^40 bytes.
    constexpr qint64 MaxMemoryMapSize =
            Q_INT64_C(1) << (sizeof(qsizetype) > 4 ? 40 : 29);
 
    qsizetype fdlen = qMin(file.size(), MaxMemoryMapSize);
    const char *filedata = reinterpret_cast<char *>(file.map(0, fdlen));
 
#ifdef Q_OS_UNIX
    if (filedata == nullptr) {
        // If we can't mmap(), then the dynamic loader won't be able to either.
        // This can't be used as a plugin.
        qCWarning(qt_lcDebugPlugins, "%ls: failed to map to memory: %ls",
                  qUtf16Printable(library), qUtf16Printable(file.errorString()));
        return false;
    }
#else
    QByteArray data;
    if (filedata == nullptr) {
        // It's unknown at this point whether Windows supports LoadLibrary() on
        // files that fail to CreateFileMapping / MapViewOfFile, so we err on
        // the side of doing a regular read into memory (up to 64 MB).
        data = file.read(64 * 1024 * 1024);
        filedata = data.constData();
        fdlen = data.size();
    }
#endif
 
    QString errMsg = library;
    QLibraryScanResult r = qt_find_pattern(filedata, fdlen, &errMsg);
    if (r.length) {
        if (!lib->metaData.parse(QByteArrayView(filedata + r.pos, r.length))) {
            errMsg = lib->metaData.errorString();
            qCWarning(qt_lcDebugPlugins, "Found invalid metadata in lib %ls: %ls",
                      qUtf16Printable(library), qUtf16Printable(errMsg));
        } else {
            qCDebug(qt_lcDebugPlugins, "Found metadata in lib %ls, metadata=\n%s\n",
                    qUtf16Printable(library),
                    QJsonDocument(lib->metaData.toJson()).toJson().constData());
            return true;
        }
    } else {
        qCDebug(qt_lcDebugPlugins, "Failed to find metadata in lib %ls: %ls",
                qUtf16Printable(library), qUtf16Printable(errMsg));
    }
 
    lib->errorString = QLibrary::tr("Failed to extract plugin meta data from '%1': %2")
            .arg(library, errMsg);
    return false;
}
 
static void installCoverageTool(QLibraryPrivate *libPrivate)
{
#ifdef __COVERAGESCANNER__
    /*
      __COVERAGESCANNER__ is defined when Qt has been instrumented for code
      coverage by TestCocoon. CoverageScanner is the name of the tool that
      generates the code instrumentation.
      This code is required here when code coverage analysis with TestCocoon
      is enabled in order to allow the loading application to register the plugin
      and then store its execution report. The execution report gathers information
      about each part of the plugin's code that has been used when
      the plugin was loaded by the launching application.
      The execution report for the plugin will go to the same execution report
      as the one defined for the application loading it.
    */
 
    int ret = __coveragescanner_register_library(libPrivate->fileName.toLocal8Bit());
 
    if (ret >= 0) {
            qDebug("coverage data for %ls registered",
                   qUtf16Printable(libPrivate->fileName));
        } else {
            qWarning("could not register %ls: error %d; coverage data may be incomplete",
                     qUtf16Printable(libPrivate->fileName),
                     ret);
        }
    }
#else
    Q_UNUSED(libPrivate);
#endif
}
 
class QLibraryStore
{
public:
    inline ~QLibraryStore();
    static inline QLibraryPrivate *findOrCreate(const QString &fileName, const QString &version, QLibrary::LoadHints loadHints);
    static inline void releaseLibrary(QLibraryPrivate *lib);
 
    static inline void cleanup();
 
private:
    static inline QLibraryStore *instance();
 
    // all members and instance() are protected by qt_library_mutex
    typedef QMap<QString, QLibraryPrivate *> LibraryMap;
    LibraryMap libraryMap;
};
 
static QBasicMutex qt_library_mutex;
static QLibraryStore *qt_library_data = nullptr;
static bool qt_library_data_once;
 
QLibraryStore::~QLibraryStore()
{
    qt_library_data = nullptr;
}
 
inline void QLibraryStore::cleanup()
{
    QLibraryStore *data = qt_library_data;
    if (!data)
        return;
 
    // find any libraries that are still loaded but have a no one attached to them
    LibraryMap::Iterator it = data->libraryMap.begin();
    for (; it != data->libraryMap.end(); ++it) {
        QLibraryPrivate *lib = it.value();
        if (lib->libraryRefCount.loadRelaxed() == 1) {
            if (lib->libraryUnloadCount.loadRelaxed() > 0) {
                Q_ASSERT(lib->pHnd.loadRelaxed());
                lib->libraryUnloadCount.storeRelaxed(1);
#ifdef __GLIBC__
                // glibc has a bug in unloading from global destructors
                // see https://bugzilla.novell.com/show_bug.cgi?id=622977
                // and http://sourceware.org/bugzilla/show_bug.cgi?id=11941
                lib->unload(QLibraryPrivate::NoUnloadSys);
#elif defined(Q_OS_DARWIN)
                // We cannot fully unload libraries, as we don't know if there are
                // lingering references (in system threads e.g.) to Objective-C classes
                // defined in the library.
                lib->unload(QLibraryPrivate::NoUnloadSys);
#else
                lib->unload();
#endif
            }
            delete lib;
            it.value() = nullptr;
        }
    }
 
    // dump all objects that remain
    if (lcDebugLibrary().isDebugEnabled()) {
        for (QLibraryPrivate *lib : qAsConst(data->libraryMap)) {
            if (lib)
                qDebug(lcDebugLibrary)
                        << "On QtCore unload," << lib->fileName << "was leaked, with"
                        << lib->libraryRefCount.loadRelaxed() << "users";
        }
    }
 
    delete data;
}
 
static void qlibraryCleanup()
{
    QLibraryStore::cleanup();
}
Q_DESTRUCTOR_FUNCTION(qlibraryCleanup)
 
// must be called with a locked mutex
QLibraryStore *QLibraryStore::instance()
{
    if (Q_UNLIKELY(!qt_library_data_once && !qt_library_data)) {
        // only create once per process lifetime
        qt_library_data = new QLibraryStore;
        qt_library_data_once = true;
    }
    return qt_library_data;
}
 
inline QLibraryPrivate *QLibraryStore::findOrCreate(const QString &fileName, const QString &version,
                                                    QLibrary::LoadHints loadHints)
{
    QMutexLocker locker(&qt_library_mutex);
    QLibraryStore *data = instance();
 
    // check if this library is already loaded
    QLibraryPrivate *lib = nullptr;
    if (Q_LIKELY(data)) {
        lib = data->libraryMap.value(fileName);
        if (lib)
            lib->mergeLoadHints(loadHints);
    }
    if (!lib)
        lib = new QLibraryPrivate(fileName, version, loadHints);
 
    // track this library
    if (Q_LIKELY(data) && !fileName.isEmpty())
        data->libraryMap.insert(fileName, lib);
 
    lib->libraryRefCount.ref();
    return lib;
}
 
inline void QLibraryStore::releaseLibrary(QLibraryPrivate *lib)
{
    QMutexLocker locker(&qt_library_mutex);
    QLibraryStore *data = instance();
 
    if (lib->libraryRefCount.deref()) {
        // still in use
        return;
    }
 
    // no one else is using
    Q_ASSERT(lib->libraryUnloadCount.loadRelaxed() == 0);
 
    if (Q_LIKELY(data) && !lib->fileName.isEmpty()) {
        QLibraryPrivate *that = data->libraryMap.take(lib->fileName);
        Q_ASSERT(lib == that);
        Q_UNUSED(that);
    }
    delete lib;
}
 
QLibraryPrivate::QLibraryPrivate(const QString &canonicalFileName, const QString &version, QLibrary::LoadHints loadHints)
    : fileName(canonicalFileName), fullVersion(version), pluginState(MightBeAPlugin)
{
    loadHintsInt.storeRelaxed(loadHints.toInt());
    if (canonicalFileName.isEmpty())
        errorString = QLibrary::tr("The shared library was not found.");
}
 
QLibraryPrivate *QLibraryPrivate::findOrCreate(const QString &fileName, const QString &version,
                                               QLibrary::LoadHints loadHints)
{
    return QLibraryStore::findOrCreate(fileName, version, loadHints);
}
 
QLibraryPrivate::~QLibraryPrivate()
{
}
 
void QLibraryPrivate::mergeLoadHints(QLibrary::LoadHints lh)
{
    // if the library is already loaded, we can't change the load hints
    if (pHnd.loadRelaxed())
        return;
 
    loadHintsInt.storeRelaxed(lh.toInt());
}
 
QFunctionPointer QLibraryPrivate::resolve(const char *symbol)
{
    if (!pHnd.loadRelaxed())
        return nullptr;
    return resolve_sys(symbol);
}
 
void QLibraryPrivate::setLoadHints(QLibrary::LoadHints lh)
{
    // this locks a global mutex
    QMutexLocker lock(&qt_library_mutex);
    mergeLoadHints(lh);
}
 
QObject *QLibraryPrivate::pluginInstance()
{
    // first, check if the instance is cached and hasn't been deleted
    QObject *obj = [&](){ QMutexLocker locker(&mutex); return inst.data(); }();
    if (obj)
        return obj;
 
    // We need to call the plugin's factory function. Is that cached?
    // skip increasing the reference count (why? -Thiago)
    QtPluginInstanceFunction factory = instanceFactory.loadAcquire();
    if (!factory)
        factory = loadPlugin();
 
    if (!factory)
        return nullptr;
 
    obj = factory();
 
    // cache again
    QMutexLocker locker(&mutex);
    if (inst)
        obj = inst;
    else
        inst = obj;
    return obj;
}
 
bool QLibraryPrivate::load()
{
    if (pHnd.loadRelaxed()) {
        libraryUnloadCount.ref();
        return true;
    }
    if (fileName.isEmpty())
        return false;
 
    Q_TRACE(QLibraryPrivate_load_entry, fileName);
 
    bool ret = load_sys();
    qCDebug(lcDebugLibrary)
            << fileName
            << (ret ? "loaded library" : qUtf8Printable(u"cannot load: " + errorString));
    if (ret) {
        //when loading a library we add a reference to it so that the QLibraryPrivate won't get deleted
        //this allows to unload the library at a later time
        libraryUnloadCount.ref();
        libraryRefCount.ref();
        installCoverageTool(this);
    }
 
    Q_TRACE(QLibraryPrivate_load_exit, ret);
 
    return ret;
}
 
bool QLibraryPrivate::unload(UnloadFlag flag)
{
    if (!pHnd.loadRelaxed())
        return false;
    if (libraryUnloadCount.loadRelaxed() > 0 && !libraryUnloadCount.deref()) { // only unload if ALL QLibrary instance wanted to
        QMutexLocker locker(&mutex);
        delete inst.data();
        if (flag == NoUnloadSys || unload_sys()) {
            qCDebug(lcDebugLibrary) << fileName << "unloaded library"
                                    << (flag == NoUnloadSys ? "(faked)" : "");
            // when the library is unloaded, we release the reference on it so that 'this'
            // can get deleted
            libraryRefCount.deref();
            pHnd.storeRelaxed(nullptr);
            instanceFactory.storeRelaxed(nullptr);
            return true;
        }
    }
 
    return false;
}
 
void QLibraryPrivate::release()
{
    QLibraryStore::releaseLibrary(this);
}
 
QtPluginInstanceFunction QLibraryPrivate::loadPlugin()
{
    if (auto ptr = instanceFactory.loadAcquire()) {
        libraryUnloadCount.ref();
        return ptr;
    }
    if (pluginState == IsNotAPlugin)
        return nullptr;
    if (load()) {
        auto ptr = reinterpret_cast<QtPluginInstanceFunction>(resolve("qt_plugin_instance"));
        instanceFactory.storeRelease(ptr); // two threads may store the same value
        return ptr;
    }
    qCDebug(qt_lcDebugPlugins) << "QLibraryPrivate::loadPlugin failed on" << fileName << ":" << errorString;
    pluginState = IsNotAPlugin;
    return nullptr;
}
 
bool QLibrary::isLibrary(const QString &fileName)
{
#if defined(Q_OS_WIN)
    return fileName.endsWith(QLatin1String(".dll"), Qt::CaseInsensitive);
#else // Generic Unix
# if defined(Q_OS_DARWIN)
    // On Apple platforms, dylib look like libmylib.1.0.0.dylib
    if (fileName.endsWith(QLatin1String(".dylib")))
        return true;
# endif
    QString completeSuffix = QFileInfo(fileName).completeSuffix();
    if (completeSuffix.isEmpty())
        return false;
 
    // if this throws an empty-array error, you need to fix the #ifdef's:
    const QLatin1String candidates[] = {
# 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."
*/
        QLatin1String("sl"),
#  if defined __ia64
        QLatin1String("so"),
#  endif
# elif defined(Q_OS_AIX)
        QLatin1String("a"),
        QLatin1String("so"),
# elif defined(Q_OS_DARWIN)
        QLatin1String("so"),
        QLatin1String("bundle"),
# elif defined(Q_OS_UNIX)
        QLatin1String("so"),
# endif
    }; // candidates
 
    auto isValidSuffix = [&candidates](QStringView s) {
        return std::find(std::begin(candidates), std::end(candidates), s) != std::end(candidates);
    };
 
    // 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
 
    auto suffixes = qTokenize(completeSuffix, u'.');
    auto it = suffixes.begin();
    const auto end = suffixes.end();
 
    auto isNumeric = [](QStringView s) { bool ok; (void)s.toInt(&ok); return ok; };
 
    while (it != end) {
        if (isValidSuffix(*it++))
            return q20::ranges::all_of(it, end, isNumeric);
    }
    return false; // no valid suffix found
#endif
}
 
static bool qt_get_metadata(QLibraryPrivate *priv, QString *errMsg)
{
    auto error = [=](QString &&explanation) {
        *errMsg = QLibrary::tr("'%1' is not a Qt plugin (%2)").arg(priv->fileName, std::move(explanation));
        return false;
    };
 
    QPluginMetaData metaData;
    QFunctionPointer pfn = priv->resolve("qt_plugin_query_metadata_v2");
    if (pfn) {
        metaData = reinterpret_cast<QPluginMetaData (*)()>(pfn)();
#if QT_VERSION <= QT_VERSION_CHECK(7, 0, 0)
    } else if ((pfn = priv->resolve("qt_plugin_query_metadata"))) {
        metaData = reinterpret_cast<QPluginMetaData (*)()>(pfn)();
        if (metaData.size < sizeof(QPluginMetaData::MagicHeader))
            return error(QLibrary::tr("metadata too small"));
 
        // adjust the meta data to point to the header
        auto data = reinterpret_cast<const char *>(metaData.data);
        data += sizeof(QPluginMetaData::MagicString);
        metaData.data = data;
        metaData.size -= sizeof(QPluginMetaData::MagicString);
#endif
    } else {
        return error(QLibrary::tr("entrypoint to query the plugin meta data not found"));
    }
 
    if (metaData.size < sizeof(QPluginMetaData::Header))
        return error(QLibrary::tr("metadata too small"));
 
    if (priv->metaData.parse(metaData))
        return true;
    *errMsg = priv->metaData.errorString();
    return false;
}
 
bool QLibraryPrivate::isPlugin()
{
    if (pluginState == MightBeAPlugin)
        updatePluginState();
 
    return pluginState == IsAPlugin;
}
 
void QLibraryPrivate::updatePluginState()
{
    QMutexLocker locker(&mutex);
    errorString.clear();
    if (pluginState != MightBeAPlugin)
        return;
 
    bool success = false;
 
#if defined(Q_OS_UNIX) && !defined(Q_OS_MAC)
    if (fileName.endsWith(QLatin1String(".debug"))) {
        // refuse to load a file that ends in .debug
        // these are the debug symbols from the libraries
        // the problem is that they are valid shared library files
        // and dlopen is known to crash while opening them
 
        // pretend we didn't see the file
        errorString = QLibrary::tr("The shared library was not found.");
        pluginState = IsNotAPlugin;
        return;
    }
#endif
 
    if (!pHnd.loadRelaxed()) {
        // scan for the plugin metadata without loading
        success = findPatternUnloaded(fileName, this);
    } else {
        // library is already loaded (probably via QLibrary)
        // simply get the target function and call it.
        success = qt_get_metadata(this, &errorString);
    }
 
    if (!success) {
        if (errorString.isEmpty()) {
            if (fileName.isEmpty())
                errorString = QLibrary::tr("The shared library was not found.");
            else
                errorString = QLibrary::tr("The file '%1' is not a valid Qt plugin.").arg(fileName);
        }
        pluginState = IsNotAPlugin;
        return;
    }
 
    pluginState = IsNotAPlugin; // be pessimistic
 
    uint qt_version = uint(metaData.value(QtPluginMetaDataKeys::QtVersion).toInteger());
    bool debug = metaData.value(QtPluginMetaDataKeys::IsDebug).toBool();
    if ((qt_version & 0x00ff00) > (QT_VERSION & 0x00ff00) || (qt_version & 0xff0000) != (QT_VERSION & 0xff0000)) {
        qCWarning(qt_lcDebugPlugins, "In %s:\n"
                 "  Plugin uses incompatible Qt library (%d.%d.%d) [%s]",
                 QFile::encodeName(fileName).constData(),
                 (qt_version&0xff0000) >> 16, (qt_version&0xff00) >> 8, qt_version&0xff,
                 debug ? "debug" : "release");
        errorString = QLibrary::tr("The plugin '%1' uses incompatible Qt library. (%2.%3.%4) [%5]")
            .arg(fileName,
                 QString::number((qt_version & 0xff0000) >> 16),
                 QString::number((qt_version & 0xff00) >> 8),
                 QString::number(qt_version & 0xff),
                 debug ? QLatin1String("debug") : QLatin1String("release"));
    } else if (PluginMustMatchQtDebug && debug != QtBuildIsDebug) {
        //don't issue a qWarning since we will hopefully find a non-debug? --Sam
        errorString = QLibrary::tr("The plugin '%1' uses incompatible Qt library."
                 " (Cannot mix debug and release libraries.)").arg(fileName);
    } else {
        pluginState = IsAPlugin;
    }
}
 
bool QLibrary::load()
{
    if (!d)
        return false;
    if (d.tag() == Loaded)
        return d->pHnd.loadRelaxed();
    else
        d.setTag(Loaded);
    return d->load();
}
 
bool QLibrary::unload()
{
    if (d.tag() == Loaded) {
        d.setTag(NotLoaded);
        return d->unload();
    }
    return false;
}
 
bool QLibrary::isLoaded() const
{
    return d && d->pHnd.loadRelaxed();
}
 
 
QLibrary::QLibrary(QObject *parent) : QObject(parent)
{
}
 
 
QLibrary::QLibrary(const QString &fileName, QObject *parent) : QObject(parent)
{
    setFileName(fileName);
}
 
QLibrary::QLibrary(const QString &fileName, int verNum, QObject *parent) : QObject(parent)
{
    setFileNameAndVersion(fileName, verNum);
}
 
QLibrary::QLibrary(const QString &fileName, const QString &version, QObject *parent)
    : QObject(parent)
{
    setFileNameAndVersion(fileName, version);
}
 
QLibrary::~QLibrary()
{
    if (d)
        d->release();
}
 
void QLibrary::setFileName(const QString &fileName)
{
    QLibrary::LoadHints lh;
    if (d) {
        lh = d->loadHints();
        d->release();
        d = {};
    }
    d = QLibraryPrivate::findOrCreate(fileName, QString(), lh);
}
 
QString QLibrary::fileName() const
{
    if (d) {
        QMutexLocker locker(&d->mutex);
        return d->qualifiedFileName.isEmpty() ? d->fileName : d->qualifiedFileName;
    }
    return QString();
}
 
void QLibrary::setFileNameAndVersion(const QString &fileName, int verNum)
{
    QLibrary::LoadHints lh;
    if (d) {
        lh = d->loadHints();
        d->release();
        d = {};
    }
    d = QLibraryPrivate::findOrCreate(fileName, verNum >= 0 ? QString::number(verNum) : QString(), lh);
}
 
void QLibrary::setFileNameAndVersion(const QString &fileName, const QString &version)
{
    QLibrary::LoadHints lh;
    if (d) {
        lh = d->loadHints();
        d->release();
        d = {};
    }
    d = QLibraryPrivate::findOrCreate(fileName, version, lh);
}
 
QFunctionPointer QLibrary::resolve(const char *symbol)
{
    if (!isLoaded() && !load())
        return nullptr;
    return d->resolve(symbol);
}
 
QFunctionPointer QLibrary::resolve(const QString &fileName, const char *symbol)
{
    QLibrary library(fileName);
    return library.resolve(symbol);
}
 
QFunctionPointer QLibrary::resolve(const QString &fileName, int verNum, const char *symbol)
{
    QLibrary library(fileName, verNum);
    return library.resolve(symbol);
}
 
QFunctionPointer QLibrary::resolve(const QString &fileName, const QString &version, const char *symbol)
{
    QLibrary library(fileName, version);
    return library.resolve(symbol);
}
 
QString QLibrary::errorString() const
{
    QString str;
    if (d) {
        QMutexLocker locker(&d->mutex);
        str = d->errorString;
    }
    return str.isEmpty() ? tr("Unknown error") : str;
}
 
void QLibrary::setLoadHints(LoadHints hints)
{
    if (!d) {
        d = QLibraryPrivate::findOrCreate(QString());   // ugly, but we need a d-ptr
        d->errorString.clear();
    }
    d->setLoadHints(hints);
}
 
QLibrary::LoadHints QLibrary::loadHints() const
{
    return d ? d->loadHints() : QLibrary::LoadHints();
}
 
/* Internal, for debugging */
bool qt_debug_component()
{
    static int debug_env = QT_PREPEND_NAMESPACE(qEnvironmentVariableIntValue)("QT_DEBUG_PLUGINS");
    return debug_env != 0;
}
 
QT_END_NAMESPACE
 
#include "moc_qlibrary.cpp"