Re: Controlled types and exception safety

["Jeffrey R. Carter" <spam@spam.com>]

Maciej Sobczak wrote:

> 1. X is finalized. This allows me to clean up (free) its internal data.
> 2. Y is *shallow-copied* to X, so that in effect X and Y share their state.
> 3. X is adjusted. This allows me to duplicate its internal structure so 
> that it becomes independent from Y.

 From ARM 7.6:

  For an assignment_statement, after the name and expression have been 
evaluated, and any conversion (including constraint checking) has been done, an 
anonymous object is created, and the value is assigned into it; that is, the 
assignment operation is applied. (Assignment includes value adjustment.) The 
target of the assignment_statement is then finalized. The value of the anonymous 
object is then assigned into the target of the assignment_statement. Finally, 
the anonymous object is finalized. As explained below, the implementation may 
eliminate the intermediate anonymous object, so this description subsumes the 
one given in 5.2, ``Assignment Statements''.

So really:

1. An intermediate object of the type is created.
2. Y's bit pattern is copied into the intermediate object.
3. The intermediate object is adjusted.
4. X is finalized.
5. The intermediate object's bit pattern is copied into X.
6. X is adjusted.
7. The intermediate object is finalized.

-- 
Jeff Carter
"Crucifixion's a doddle."
Monty Python's Life of Brian
82