Re: [Tarantool-patches] [PATCH 5/7] box/error: clarify purpose of reference counting in struct error

[Nikita Pettik <korablev@tarantool.org>]

On 23 Feb 18:43, Vladislav Shpilevoy wrote:
> Thanks for the patch!
> 
> How about merging this commit into the previous one?
> 
> On 19/02/2020 15:16, Nikita Pettik wrote:
> > ---
> >  src/lib/core/diag.h | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> > 
> > diff --git a/src/lib/core/diag.h b/src/lib/core/diag.h
> > index 5271733cb..a9181c522 100644
> > --- a/src/lib/core/diag.h
> > +++ b/src/lib/core/diag.h
> > @@ -72,6 +72,15 @@ struct error {
> >  	error_f raise;
> >  	error_f log;
> >  	const struct type_info *type;
> > +	/**
> > +	 * Reference counting is basically required since
> > +	 * instances of this structure are available in Lua
> > +	 * as well (as cdata with overloaded fields and methods
> > +	 * by the means of introspection). Thus, it may turn
> > +	 * out that Lua's GC attempts at releasing object
> > +	 * meanwhile it is still used in C internals or vice
> > +	 * versa. For details see luaT_pusherror().
> 
> Hmm, no, it can't anymore.

Now it can't. But it used to, until ref in luaT_pusherror() was
introduced. So may comment refer to that quite ancient fix (I just
wondered why can't we get rid of ref counter and came up with
this explanation).

> Lua can't delete an error object,
> if it is still used in C. This looks like an artifact from the
> previous patch version, were you unreferenced all errors when
> diag was cleared.
> 
> > +	 */
> >  	int refs;
> >  	/**
> >  	 * Errno at the moment of the error
> >