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

Przemek Kitszel
2024-10-02T09:55:56Z

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