CODEWITHSUNDEEP
c++qt
Paul
Paul

Reputation: 26640

Strange QString initialization with 0 - what does it do?

Sorry, but I can't find a right place in C++ manual.

In a following string:

void setYRange(QString name1, int s1, int e1, QString name2 = 0, int s2 = 0, int e2 = 0);

I do not understand the initialization:

QString name2 = 0

Please give me just a reference to the right place in C++ manual.

Upvotes: 1

Views: 364

Answers (1)

NathanOliver
NathanOliver

Reputation: 180415

What you are seeing is the compiler choosing the QString::QString(const QChar *unicode, int size = -1) constructor. 0 is the null pointer value so a pointer can be implicitly constructed from it. That means to compiler will chose the c-string constructor and initialize the pointer to a null pointer. Since the pointer is null and that means you will construct an null QString(it is empty).

Do note that this behavior is different from a std::string. Constructing one of those from a null pointer is undefined behavior.

Upvotes: 2

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