Re: [RFC PATCH v2] Simply enable one to write code like:

[Przemek Kitszel]

On 10/1/24 17:21, Dmitry Torokhov wrote:
> Hi Przemek,
>
> On Tue, Oct 01, 2024 at 04:57:18PM +0200, Przemek Kitszel wrote:
> > int foo(struct my_drv *adapter)
> > {
> > 	scoped_guard(spinlock, &adapter->some_spinlock)
> > 		return adapter->spinlock_protected_var;
> > }
>
> Could you change the subject to say something like:
>
> "Adjust cond_guard() implementation to avoid potential warnings"
>
> And then give detailed explanation in the body?

thanks, sure
(and apologies that I forgot to add any subject :F (this was just my
very first non-subject paragraph))

> > Current scoped_guard() implementation does not support that,
> > due to compiler complaining:
> > error: control reaches end of non-void function [-Werror=return-type]
> >
> > One could argue that for such use case it would be better to use
> > guard(spinlock)(&adapter->some_spinlock), I disagree. I could also say
> > that coding with my proposed locking style is also very pleasant, as I'm
> > doing so for a few weeks already.
>
> I'd drop this paragraph from the patch description (and moved past "---"
> if you prefer to keep it for additional context.

I will think about that, especially given that since v2 this patch is
not only fixing "my case", but just it's regular hardening for static
analysis needs.


> > +#define DEFINE_CLASS_IS_CONDITIONAL(_name, _is_cond)	\
>
> This is not supposed to be used outside of cleanup.h so probably
> __DEFINE_CLASS_IS_CONDITIONAL()?

indeed

> > +#define __scoped_guard_labeled(_label, _name, args...)	\
> > +	if (0)						\
> > +		_label: ;				\
> > +	else						\
> > +		for (CLASS(_name, scope)(args);		\
> > +		     __guard_ptr(_name)(&scope) || !__is_cond_ptr(_name); \
> > +		     ({goto _label;}))
>
> The "jump back" throws me a little, do you think if can be rewritten as:
>
> 	if (true)
> 		for (...)
> 	else
> 		_label: /* dummy */ ;

user code must be glued at the end, so there must be "if (0) label:"
however I figured that you could reorder for and else:

	for (
		CLASS(...);
		__guard_ptr(...) || __is_cond_ptr(...);
		({ goto label; })
	)
		if (0)
			label:
				break;
		else
			// actual user code glued here

and this jumps forward

> >   
> >   #define scoped_cond_guard(_name, _fail, args...) \
> >   	for (CLASS(_name, scope)(args), \
>
> With your __is_cond_ptr() can this be made to warn or error if
> scoped_cond_guard() is used with a non-conditional lock/class? As that
> would make no sense.

good idea, thanks