Assignment Operator with auto_ptr

[Chummaid]

Hello All,
Can somebody please explain why the following is not supported ?

class A{};

A* a = new A();

auto_ptr <A> aptr = *a;

// though this is supported.

auto_ptr <A> aptr(a);

Thanks in advance
CID

[Kristo]

[e-mail] wrote:

Hello All,
Can somebody please explain why the following is not supported ?

class A{};

A* a = new A();

auto_ptr <A> aptr = *a;
Contrary to what the thread subject says, this invokes auto_ptr's
constructor. You're trying to pass the A object itself, not a pointer
to it. This is the correct way to do it:
// though this is supported.

auto_ptr <A> aptr(a);

If you want to use the equals sign syntax, this line would be:
auto_ptr<A> aptr = a;

Kristo

[CID]

Kristo wrote:

[e-mail] wrote:

Hello All,
Can somebody please explain why the following is not supported ?

class A{};

A* a = new A();

auto_ptr <A> aptr = *a;
Contrary to what the thread subject says, this invokes auto_ptr's
constructor. You're trying to pass the A object itself, not a

pointer to it. This is the correct way to do it:

// though this is supported.

auto_ptr <A> aptr(a);

If you want to use the equals sign syntax, this line would be:
auto_ptr<A> aptr = a;

Kristo

This will result in the following error in g++, which was my first
doubt was.

error: conversion from `A*' to non-scalar type
`std::auto_ptr<A>' requested

Thanks for the reply
CID

[Stefan Strasser]

CID schrieb:

Kristo wrote:

[e-mail] wrote:

Hello All,
Can somebody please explain why the following is not supported ?

class A{};

A* a = new A();

auto_ptr <A> aptr = *a;

Contrary to what the thread subject says, this invokes auto_ptr's
constructor. You're trying to pass the A object itself, not a

pointer

to it. This is the correct way to do it:

// though this is supported.

auto_ptr <A> aptr(a);

If you want to use the equals sign syntax, this line would be:
auto_ptr<A> aptr = a;

Kristo

This will result in the following error in g++, which was my first
doubt was.

error: conversion from `A*' to non-scalar type
`std::auto_ptr<A>' requested

that's because the constructor of auto_ptr is "explicit", and there's a
obvious reason for it.
use
auto_ptr<A> aptr=auto_ptr<A>(a);
instead