Reference to temporary objects

[Alexander Stippler]

Here my code snippet:

//----------------------

struct Thing
{
};

template <typename T>
struct Wrap
{
operator T &()
{
return t;
} }

T t;
};

Wrap<Thing>
func()
{
return Wrap<Thing>();
}

//------------------------

And here my question:

// 1) Ok, lifetime of returned temporary is bound to "a"
const Wrap<Thing> &a = func();

// 2) Not allowed, why?
Wrap<Thing> &a = func();

// 3) Not ok. "a" references an object that gets destroyed
Thing &a = func()

Here my questions:

why is 2) not allowed?

regarding 3):
I was reading 12.2 in the standard:
"The second context is when a reference is bound to a temporary. The
temporary to which the reference is bound or the temporary that is the
complete object to a subobject of which the temporary is bound persists
for the lifetime of the reference except as specified below".

Well I couldn't see that the "things below" match.

[Rolf Magnus]

Alexander Stippler wrote:

Here my code snippet:

//----------------------

struct Thing
{
};

template <typename T>
struct Wrap
{
operator T &()
{
return t;
} }

T t;
};

Wrap<Thing>
func()
{
return Wrap<Thing>();
}

//------------------------

And here my question:

// 1) Ok, lifetime of returned temporary is bound to "a"
const Wrap<Thing> &a = func();
Right.
// 2) Not allowed, why?
Wrap<Thing> &a = func();
Because C++ forbids binding non-const references to temporaries.
// 3) Not ok. "a" references an object that gets destroyed
Thing &a = func()

Right.