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diff --git a/sources/shiboken6/ApiExtractor/conditionalstreamreader.h b/sources/shiboken6/ApiExtractor/conditionalstreamreader.h
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+++ b/sources/shiboken6/ApiExtractor/conditionalstreamreader.h
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+// Copyright (C) 2021 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only WITH Qt-GPL-exception-1.0
+
+#ifndef CONDITIONALSTREAMREADER_H
+#define CONDITIONALSTREAMREADER_H
+
+#include <QtCore/QXmlStreamReader>
+
+#include <utility>
+
+QT_FORWARD_DECLARE_CLASS(QDebug)
+
+class ProxyEntityResolver;
+
+/// ConditionalStreamReader encapsulates QXmlStreamReader, offering the same
+/// API (except readNextStartElement() and similar conveniences) and internally
+/// uses Processing Instructions like:
+///   <?if keyword1 !keyword2?> ... <?endif?>
+/// to exclude/include sections depending on a list of condition keywords,
+/// containing for example the OS.
+/// It should be possible to use it as a drop-in replacement for
+/// QXmlStreamReader for any parsing code based on readNext().
+/// It also allows for specifying entities using a Processing Instruction:
+/// <?entity name value?>
+/// which can be used in conjunction with conditional processing.
+class ConditionalStreamReader
+{
+public:
+    Q_DISABLE_COPY_MOVE(ConditionalStreamReader)
+
+    using TokenType = QXmlStreamReader::TokenType;
+    explicit ConditionalStreamReader(QIODevice *iod);
+    explicit ConditionalStreamReader(const QString &s);
+    ~ConditionalStreamReader();
+
+    QIODevice *device() const { return m_reader.device(); }
+
+    // Note: Caching of entity values is done internally by
+    // ConditionalStreamReader.
+    void setEntityResolver(QXmlStreamEntityResolver *resolver);
+    QXmlStreamEntityResolver *entityResolver() const;
+
+    bool atEnd() const { return m_reader.atEnd(); }
+    TokenType readNext();
+
+    TokenType tokenType() const { return  m_reader.tokenType(); }
+
+    qint64 lineNumber() const { return m_reader.lineNumber(); }
+    qint64 columnNumber() const { return m_reader.columnNumber(); }
+
+    QXmlStreamAttributes attributes() const { return m_reader.attributes(); }
+
+    QString readElementText(QXmlStreamReader::ReadElementTextBehaviour behaviour = QXmlStreamReader::ErrorOnUnexpectedElement)
+    { return m_reader.readElementText(behaviour); }
+
+    QStringView name() const { return m_reader.name(); }
+    QStringView qualifiedName() const { return m_reader.qualifiedName(); }
+
+    QStringView text() const { return m_reader.text(); }
+
+    QString errorString() const { return m_reader.errorString(); }
+    QXmlStreamReader::Error error() const { return m_reader.error(); }
+
+    bool hasError() const { return m_reader.hasError(); }
+
+    // Additional functions (not delegating to QXmlStreamReader)
+    void defineEntity(const QString &name, const QString &value);
+
+    const QStringList &conditions() const { return m_conditions; }
+    void setConditions(const QStringList &newConditions);
+
+    static QStringList platformConditions();
+
+private:
+    enum class PiTokens { None, If, Endif, EntityDefinition };
+
+    using ExtendedToken = std::pair<TokenType, PiTokens>;
+    ExtendedToken readNextInternal();
+    void init();
+    bool conditionMatches() const;
+    bool readEntityDefinitonPi();
+
+    QXmlStreamReader m_reader;
+    ProxyEntityResolver *m_proxyEntityResolver = nullptr;
+    QStringList m_conditions = ConditionalStreamReader::platformConditions();
+};
+
+QDebug operator<<(QDebug dbg, const QXmlStreamAttributes &a);
+
+#endif // CONDITIONALSTREAMREADER_H