On 06.06.2012 20:53, Sean Kelly wrote:
On Jun 6, 2012, at 9:45 AM, deadalnix wrote:
Le 05/06/2012 18:21, Sean Kelly a écrit :
On Jun 5, 2012, at 8:44 AM, Jonathan M Davis<[email protected]> wrote:
In many cases, it's probably fine, but if the program is in a bad enough state
that an Error is thrown, then you can't know for sure that any particular such
block will execute properly (memory corruption being the extreme case), and if
it doesn't run correctly, then it could make things worse (e.g. writing
invalid data to a file, corrupting that file). Also, if the stack is not unwound
perfectly (as nothrow prevents), then the program's state will become
increasingly invalid the farther that the program gets from the throw point,
which will increase the chances of cleanup code functioning incorrectly, as
any assumptions that they've made about the program state are increasingly
likely to be wrong (as well as it being increasingly likely that the variables
that they operate on no longer being valid).
Then we should really just abort on Error. What I don't understand is the
assertion that it isn't safe to unwind the stack on Error and yet that
catch(Error) clauses should still execute. If the program state is really so
bad that nothing can be done safely then why would the user attempt to log the
error condition or anything else?
Yes, either we consider the environement may have been compromised and it don't
even make sense to throw an Error, or we consider this environement is still
consistent, and we have a logic bug. If so, scope (especially failure) should
run when stack is unwinded.
As need depend on the software (an office suite should try its best to fail
gracefully, a plane autpilot should crash ASAP and give control back to the
pilot), what is needed here is a compiler switch.
I think a runtime hook is reasonable instead. But the default case has to be
the more permissive case.
It's safe to tighten the rules but never to loosen them, since external code
will be written assuming the default behavior.
Yes, that's what I had in mind when I renamed topic to "runtime hook for
Crash on Error". Default should be treat Error as just another type of
throwable that is logically not caught by catch(Exception).
--
Dmitry Olshansky
