Will the function unicode() always return the same address in the lifetime of a QString object?

[okellogg]

Hi,

If we define an object of type QString, is it safe to do pointer calculations using the return value from QString::unicode()?

As an example, see
https://github.com/KDE/kdevelop/blob/3.5/lib/cppparser/lexer.h#245

 inline const CHARTYPE* offset( int offset ) const {
    return m_source.unicode() + offset;
}

inline int getOffset( const QChar* p ) const {
    return int(p - (m_source.unicode()));
}

Let's say that usrPtr is initially assigned from m_source.unicode(), then lots of operations are done on m_source, and later m_source.getOffset(usrPtr) is called. Will the value returned still be "compatible" with usrPtr? Or is it possible that a different buffer (i.e. different start address) may be returned?

[jeremy_k]

From the documentation https://doc.qt.io/qt-6/qstring.html#unicode:

The result remains valid until the string is modified.

If the operations only involve const member functions, storing the pointer is fine. Otherwise, there is no guarantee. It's worth noting that there are some functions, such as operator[], that have both const and non-const versions.

[jsulm]

This post is deleted!