Calling abort() on unhandled exception (page 3)

----- Original Message ----
> From: Andrei Alexandrescu <andrei at erdani.com>
> To: Discuss the phobos library for D <phobos at puremagic.com>
> Sent: Fri, July 30, 2010 1:01:57 AM
> Subject: Re: [phobos] Calling abort() on unhandled exception
> 
> Sean Kelly wrote:
> > On Jul 29, 2010, at 9:37 PM, Andrei Alexandrescu  wrote:
> > 
> >> Sean Kelly wrote:
> >>> On Jul 29, 2010,  at 8:21 PM, Walter Bright wrote:
> >>>> Andrei Alexandrescu  wrote:
> >>>>> Walter Bright wrote:
> >>>>>>  I think we misunderstand each other. A file copy program that fails due
>to, say,  the disk being full, should not produce a core dump. It should produce an error  message like:
> >>>>>> 
> >>>>>> error:  disk full
> >>>>>> 
> >>>>>> An uncaught  exception is NOT an invalid or crashed program
> >>>>>>   in D.
> >>>>> I think Sean talks about Throwable objects that  are not Exception
>objects.
> >>>>> 
> >>>> It's  reasonable for seg fault exceptions to produce a core dump. It isn't
>for  recoverable Exceptions, or for non-recoverable ones like out of  memory.
> >>> At the moment, we don't differentiate between seg faults  and
>non-recoverable errors.  Though seg faults are only thrown as  exceptions on Windows which doesn't have core dumps anyway, as far as I know.  For what it's worth, I was investigating this bug:
> >>>   http://d.puremagic.com/issues/show_bug.cgi?id=4385
> >> I see. Overall,  my opinion is that regular exceptions that escape main(0
>should simply print  their error message to stderr and exit(1). There should be no stack trace,  abort(), core dump, or anything worse than that. Print the string and exit(1).  Anything more will force most people to actually insert a try/catch in  main
> >>  to do the simple thing.
> > 
> > I think the  stack trace at least should remain. People have been begging for
>that for years,  and I do think it's pretty useful. Simply
> > printing an error message says  nothing about the context, and it's context that gives error messages  meaning.
> 
> I for one really enjoy stuff like:
> 
> void main(string[]  args)
> {
>     enforce(args.length > 1, "Usage: prog  arg");
>     ...
> }

void usageEnforce(bool condition)
{
  if(!condition)
  {
     writeln("Usage: prog arg");
     exit(1);
  }
}

Please, let's leave stack traces for exceptions that escape main.  It's not a condition that most developers plan on happening.  When the unexpected exception happens, you can be lost without a stack trace.  All you get is something like this:

Uncaught exception in someModuleYouDidntWrite(123): parameter should be > 0

I do hope to see better stack traces than what we currently get though...

-Steve

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