Re: efficient exception handling

From:
=?UTF-8?B?RXJpayBXaWtzdHLDtm0=?= <Erik-wikstrom@telia.com>
Newsgroups:
comp.lang.c++
Date:
Wed, 17 Oct 2007 12:17:56 GMT
Message-ID:
<U3nRi.11592$ZA.7658@newsb.telia.net>
On 2007-10-17 13:12, terminator wrote:

On Oct 16, 7:02 pm, "Bo Persson" <b...@gmb.dk> wrote:

terminator wrote:

: On Oct 15, 1:17 pm, Erik Wikstr??m <Erik-wikst...@telia.com> wrote:
::
:: Consider the following, an exception is thrown in a constructor.
:: In the catch-block you use continue to resume the execution which
:: means that
:: your code will continue to run and try to perform operations on a
:: not
:: fully constructed object. Not a good idea. The reason the
:: exception was thrown was that correct execution was no longer
:: possible, the only
:: correct way of handling this is to go back a little and then deal
:: with
:: the situation (by aborting, trying again, trying something
:: different, etc.).
::
:
: I see : Since throw is usually used as a conditional jump, the next
: instruction is executed with the assumption that oposite of the
: condition is true where a continue can not fix the affected data.
: The solution is easy ,one must avoid a 'continue'd catch block for
: old exception classes thrown by hopeless outdated algorithms that
: do not consider a second chance .
:
: A 'throw' statement can reflect the source of error instead of just
: nagging:
:
: class foo{
: public:
: foo()throw(foo*){
: if(some_problem)
: throw this;
: };
: };

If the constructor throws, there will be no foo object. The this
pointer has nothing to point to!


If you view the post carfully ,you`ll find that On Oct 15, 10:44 am,
I wrote:


[snip previous posted text]

I have not found the relevant sections of the standard, but TC++PL says
that an object is not considered created until its constructor is done.
What that means is that even if you do not unwind the stack there is no
object if the constructor throws.

--
Erik Wikstr??m

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