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Date: Fri, 9 Aug 2019 02:33:27 +0300
From: Alexander Turenko <alexander.turenko@tarantool.org>
Subject: [tarantool-patches] Re: [PATCH v1 3/3] box: extend ffi error object
 API
Message-ID: <20190808233327.sjm76nwf2qhxd4io@tkn_work_nb>
References: <cover.1564657285.git.kshcherbatov@tarantool.org>
 <47d9072e60bdc563c7466a4e51db1a61bc71a610.1564657285.git.kshcherbatov@tarantool.org>
 <55d56797-f937-4088-fdba-7d9dfef51ae6@tarantool.org>
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To: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Cc: tarantool-patches@freelists.org, Kirill Shcherbatov <kshcherbatov@tarantool.org>, kostja@tarantool.org

> > +box_error_unwrap(box_error_t *error)
> > +{
> > +	struct error *reason = error->reason;
> > +	assert(reason != NULL);
> > +	diag_set_error(diag_get(), reason);
> > +	error_unref(reason);
> > +	error->reason = NULL;
> > +	return reason;
> 
> 7. Unwrap does not allow to unwrap a leaf error.
> But there is no API to determine if the error is
> leaf. So a user can't determine when to stop calling
> unwrap.
> 
> I am talking about C public API which you have changed
> here. A user can't check error->reason != NULL before
> calling box_error_unwrap.
> 
> Moreover, it is inconsistent with Lua version. Lets
> better return the argument when error->reason == NULL
> in box_error_unwrap. Then a user of the C API would
> just unwrap the stack until box_error_unwrap(e) == e.
> Also it simplifies Lua version implementation.

Why not just return NULL when there is no a reason? It seems to be more
logical for me.