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Re: cannot pass objects of non-POD type


On Wed, Oct 24, 2007 at 01:37:25PM -0700, Andrew Pinski wrote:
> On 10/24/07, Jack Lloyd <lloyd@randombit.net> wrote:
> > Is there a reason it's not just an error, then? (As a user) I don't
> > see the point of something being a warning when the compiled code is
> > intentionally set up to crash.
> 
> Because the C++ standard (and the C standard) has mentioned that you
> cannot diagnostic an undefined runtime behavior.  So the code is valid
> semantically but undefined at runtime.

But the way that the object is passed in this case, and the stack layout,
are completely defined on any platform that obeys the cross-platform API
you will find at

http://www.codesourcery.com/cxx-abi/

and this definition specifies that everything will look exactly the same
as if it were a POD with the same members declared in the same order.
For that reason, while I'm not surprised by the warning message, I
am surprised that the code crashes; it would seem to require extra
work to make it do so.

Not that I would support this particular programming style;
varargs/stdargs gives up type safety and risks runtime errors.


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