Re: Sequence points in new operator and constructor

From:

daniel.kruegler@googlemail.com

Newsgroups:

comp.lang.c++.moderated

Date:

Thu, 18 Dec 2008 18:08:57 CST

Message-ID:

<88964674-9def-492b-871a-a81a724884d6@a26g2000prf.googlegroups.com>

On 10 Dez., 16:33, Chaos.A....@gmail.com wrote:

Hi, can somebody please describe me one point?
How many sequence points there in this statement:
Foo *f = new Foo(Fn());

It interests me because of exception safety...
We knew, that one of the ways to write exception safe is to use RAII
idiom.
And let's consider that Fn() in my example returns pointer on some
dynamically allocated object. And Foo in it's constructor grabs it's
ownership.
So, this code will be exception safe if there is a sequence point
between memory allocation (new operator), which may throw
std::bad_alloc, and constructor.

Is there any guarantee that new never throws it's exception AFTER left
side with all arguments starts calculating?

I apologize for the second posting immediately following the first
one (whenever each one will be accepted...), but I just see that
not only

http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#292

but also

http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#672

is going to handle the here discussed situation. Especially
the last issue seem to introduce a proper sequence point
between initialization of the allocated object and value
computation of the new expression.

Greetings from Bremen,

Daniel

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