Re: [PATCH] qga/commands-posix: Make ga_wait_child() return boolean

[Zhao Liu]

On Mon, Jul 15, 2024 at 11:59:29AM +0200, Philippe Mathieu-Daudé wrote:
> Date: Mon, 15 Jul 2024 11:59:29 +0200
> From: Philippe Mathieu-Daudé <philmd@linaro.org>
> Subject: Re: [PATCH] qga/commands-posix: Make ga_wait_child() return boolean
> 
> On 15/7/24 11:59, Zhao Liu wrote:
> > As the comment in qapi/error, dereferencing @errp requires
> > ERRP_GUARD():
> > 
> > * = Why, when and how to use ERRP_GUARD() =
> > *
> > * Without ERRP_GUARD(), use of the @errp parameter is restricted:
> > * - It must not be dereferenced, because it may be null.
> > ...
> > * ERRP_GUARD() lifts these restrictions.
> > *
> > * To use ERRP_GUARD(), add it right at the beginning of the function.
> > * @errp can then be used without worrying about the argument being
> > * NULL or &error_fatal.
> > *
> > * Using it when it's not needed is safe, but please avoid cluttering
> > * the source with useless code.
> > 
> > Though currently ga_run_command() only gets &local_err instead of NULL
> > @errp, it's still better to follow the requirement to add the
> > ERRP_GUARD().
> > 
> > But as error.h suggested, the best practice for callee is to return
> > something to indicate success / failure.
> > 
> > So make ga_wait_child() return boolean and check the returned boolean in
> > ga_run_command() instead of dereferencing @errp, which eliminates the
> > need of ERRP_GUARD().
> 
> I'd avoid mentioning ERRP_GUARD and just describe:
> 
>   Make ga_wait_child() return boolean and check the returned boolean
>   in ga_run_command() instead of dereferencing @errp.
> 
> For the code change:
> 
> Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>

Many thanks for your words and review!

Will use your words in the next version.