initializer list question

[spipyeah]

My compiler is known not to be very compliant. So I can't base myself
on the fact that the following doesn't work to determine whether or
not it is legal C++.

In an initializer list, can you pass objects as parameters (by
reference or otherwise) to other objects constructed later in the
initializer list?

Example:


class Obj
{
public:
Obj( int a ) {};
};

class ObjConsumer
{
public:
ObjConsumer( Obj &first_obj, Obj &second_obj ) {};
};

class myclass
{
public:
myclass();

protected:
Obj obj1, obj2;
ObjConsumer consumer;
};

myclass::myclass() :
obj1(5),
obj2(7),
consumer( obj1, obj2 )
{
}

 

[Karl Heinz Buchegger]

My compiler is known not to be very compliant. So I can't base myself
on the fact that the following doesn't work to determine whether or
not it is legal C++.

In an initializer list, can you pass objects as parameters (by
reference or otherwise) to other objects constructed later in the
initializer list?

The tricky point is that the order in which you put things in the
initializer list doesn't affect the order in which things get constructed.

The base class will always be constructed first.
Then the member objects of that class get constructed in the
order in which they appear in the class declaration:

class myclass
{
public:
myclass();

protected:
Obj obj1, obj2; // obj1 will be constructed first

// obj2 will be constructed second

ObjConsumer consumer; // consumer will be constructed third
};

myclass::myclass() :
obj1(5),
obj2(7),
consumer( obj1, obj2 )

You could turn this around

consumer( obj1, obj2 ),
obj2( 7 ),
obj1( 5 )

yet the construction and thus the initialization sequence will be:

obj1, obj2, consumer

 

[Gary Labowitz]

My compiler is known not to be very compliant. So I can't base myself
on the fact that the following doesn't work to determine whether or
not it is legal C++.

In an initializer list, can you pass objects as parameters (by
reference or otherwise) to other objects constructed later in the
initializer list?

Example:


class Obj
{
public:
Obj( int a ) {};
};

class ObjConsumer
{
public:
ObjConsumer( Obj &first_obj, Obj &second_obj ) {};
};

class myclass
{
public:
myclass();

protected:
Obj obj1, obj2;
ObjConsumer consumer;
};

myclass::myclass() :
obj1(5),
obj2(7),
consumer( obj1, obj2 )
{
}

Did you try this? It works fine. Of course, it doesn't DO anything.

 

[spipyeah]

You could turn this around

consumer( obj1, obj2 ),
obj2( 7 ),
obj1( 5 )

yet the construction and thus the initialization sequence will be:

obj1, obj2, consumer

Thank you, that was very helpful!

Alban