🚀 go-pugleaf

Herb Sutter (herbs@interlog.com) wrote:
|> In article <9511141105.AA01230@lts.sel.alcatel.de>,
|>    James Kanze US/ESC 60/3/141 #40763 <kanze@lts.sel.alcatel.de> wrote:
|> >|> >Another interesting case:
|> >|> >
|> >|> >    A                   a1 ;
|> >|> >    A                   a2 ;
|> >|> >    A                   a3 ;
|> >|> >    //  ...
|> >|> >
|> >|> >The constructor of a2 throws an exception 
|> >|>
|> >|> Trying the above under BC++ 4.52, A::A() is called twice and then
|> >|> A::~A() is called once, which is correct.
|> >
|> >The only compiler I have access to that supports exceptions is Sun CC
|> >4.0.1; this is the compiler I used for my initial tests.  I modified
|> >the test to call exit, instead of throwing an exception, and got the
|> >following results:
|> >
|> >                                  ctors   dtors
|> >    Sun CC 4.0.1 (w/ exceptions)            2   3
|> >    Sun CC 2.1                  2       0
|> >    Cfront 3.0.1 (direct port, not from Sun)    2   3
|> >    g++ 2.6.3                   2   0
|> >    g++ 2.7.0                   2   0

|> Hold on... you changed the question! :-)  If I modify my BC++ 4.52 program

I had to.  The Cfront based compilers and g++ don't support exceptions!

|> to call exit() (instead of throwing) in a2's ctor, I get the incorrect
|> result of  three A::~A() calls.  If I change it to call abort() in a2's
|> ctor, I get zero A::~A()s.

|> Does the WP specify what/how dtors should be called in the case of an
|> exit() or abort()?

Yes and no.  In the case of abort, it is explicit: no destructors are
called.  In the case of exit...  I can find no statement forbidding
calling exit from a constructor, or saying that it is undefined
behavior.  So one must suppose that it is permitted.  But calling a
destructor on an uninitialized object will forceably result in undefined
behavior.  Whence I conclude that an implementation may not generate
code which does so *unless* my program already contains undefined
behavior.
-- 
James Kanze           (+33) 88 14 49 00          email: kanze@gabi-soft.fr
GABI Software, Sarl., 8 rue des Francs Bourgeois, 67000 Strasbourg, France
Conseils, itudes et rialisations en logiciel orienti objet --
              -- A la recherche d'une activiti dans une region francophone
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