[Development] Proposal: adding Q_DECL_NOEXCEPT to many methods

[Thiago Macieira]

On quinta-feira, 2 de agosto de 2012 16.02.43, Marc Mutz wrote:
> Need to be careful with templates. Can't use add the unrestricted noexcept 
> there, need to use noexcept(noexcept(expr)), which is even uglier

template<typename T> inline uint qHash(const T &t, uint seed)
    Q_DECL_NOEXCEPT_EXPR(noexcept(qHash(t)))
{ return (qHash(t) ^ seed); }

template <typename T1, typename T2> inline uint qHash(const QPair<T1, T2> 
&key, uint seed = 0)
    Q_DECL_NOEXCEPT_EXPR(noexcept(qHash(key.first, seed)) && 
noexcept(qHash(key.second, seed)))
{
...
}

By the way, I'm running into an issue which I'm not entirely sure whether it's 
a design issue. Imagine this case:

class Object
{
    void f();
    void g() noexcept(same noexcept status as f);
};

That is, I want to declare g to be as noexcept as its sibling function f. How? 
All of these options fail:

noexcept(noexcept(f))
 -> evaluates to true
noexcept(noexcept(Object::f))
 -> error: invalid use of non-static member function ‘void Object::f()'
noexcept(noexcept(f()))
 -> error: cannot call member function ‘void Object::f()’ without object
noexcept(noexcept(this->f()))
 -> error: invalid use of ‘this’ at top level
noexcept(noexcept(Object().f()))
 -> error: invalid use of incomplete type ‘struct Object’

Any suggestions?

My actual use-case is of a function declared in a base-class: I want 
QMutex::lock() to be noexcept if QBasicMutex::lockInternal() is noexcept. In 
that particular case, it works like this:

class QMutex : public QBasicMutex
{
    static QBasicMutex *dummyBasicMutex() noexcept;
public:
    void lock() noexcept(noexcept(dummyBasicMutex()->lockInternal()));
};

But it's ugly.
-- 
Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
   Software Architect - Intel Open Source Technology Center
      PGP/GPG: 0x6EF45358; fingerprint:
      E067 918B B660 DBD1 105C  966C 33F5 F005 6EF4 5358
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