[PATCH v2] lib: fix pointer of type 'void *' used in arithmetic

[Damien Le Moal]

On 2022/01/13 20:03, Jukka Laitinen wrote:
> Thanks for comments!
> 
> 
> On 13.1.2022 12.52, Damien Le Moal wrote:
>> [Re-sending this since my emails end up being empty...]
>>
>> On 2022/01/13 17:49, Jukka Laitinen wrote:
>>> Using "void *" in arithmetic causes errors with strict compiler settings:
>>> "error: pointer of type 'void *' used in arithmetic [-Werror=pointer-arith]"
>>>
>>> Just remove these by calculating on "char *" where 1-byte data size is assumed
>> s/Just Remove/Avoid
>> (and nit: add a period at the end of the sentence)
> 
> I will add these to patchset v3 !
> 
>>
>> I would also suggest a cast to unsigned long instead of char *. unsigned long is
>> more common/natural for addresses arithmetic.
> 
> You are right, that is is more natural to do arithmetic on integers than 
> pointers.
> 
> However, I don't like to change pointer to unsigned long and back for 
> several reasons; one being that afaik no stardard states that 
> sizeof(unsigned long) == sizeof(void *). And even while this is a 
> typical case, there is quarantee that this wouldn't have other side 
> effects (such as padding bits ...).

Well, unlike Linux kernel, the nice thing with OpenSBI is that we only need this
unsigned long cast to work on risc-v 32 and 64. And as far as I know, it does,
and that is mandated by the RISC-V ISA specs.

> 
> There is intptr_t and uintptr_t in C99 as optional for this purpose, but 
> those don't exist in all C/C++ standards.
> 
> So; I'd rather just do pointer arithmetic when the intention is to do 
> pointer arithmetic :)
> 
> 


-- 
Damien Le Moal
Western Digital Research