[Development] QVariant and types with throwing dtors

[Thiago Macieira]

On Monday 26 August 2024 10:39:56 GMT-7 Marc Mutz via Development wrote:
> On 26.08.24 08:43, Ville Voutilainen wrote:
> >> IMHO, (1) is not an acceptable option. Us C++ professionals having
> >> identified this problem after years of it lying dormant, it behooves us,
> >> at the very least, to educate our users about this, e.g. by adding docs,
> >> and maybe a qWarning() in ~QVariant(), if we don't do (2).
> > 
> > If it's not an issue, why is (1) unacceptable?
> 
> It's _guesstimated_ to be no issue, based on sampling qt5.git and
> qt-creator.git.
> 
> What is unacceptable in (1) (doing nothing) is not even _informing_
> users about what we found¹, so _they_ can decide for themselves what to do.
> 
> ¹ neither at compile-time, nor runtime, nor coding time (static checker)
>    nor at documentation reading time.
> 
> We want our APIs to be easy to use and hard to abuse. It's easy to abuse
> QVariant in this way, so it behooves us to try to do _something_ about it.

A runtime warning is unacceptable because it adds to the cost of the 99.99% 
who don't have a throwing destructor.

A compile-time warning implies having a way to disable it with "I know that, 
just ignore it" which is maintenance for us. My problem with this is the cost 
on us, to maintain such a thing that has never been a problem and likely never 
will.

-- 
Thiago Macieira - thiago.macieira (AT) intel.com
  Principal Engineer - Intel DCAI Platform & System Engineering
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