Re: [patch V3 01/10] cleanup: Provide retain_ptr()

[Thomas Gleixner]

On Mon, Mar 17 2025 at 09:57, James Bottomley wrote:
> On Mon, 2025-03-17 at 14:29 +0100, Thomas Gleixner wrote:
>> +#define retain_ptr(p)				\
>> +	__get_and_null(p, NULL)
>
> This doesn't score very highly on the Rusty API design scale because it
> can be used anywhere return_ptr() should be used.  To force the
> distinction between the two cases at the compiler level, should there
> be a cast to void in the above to prevent using the return value?

Indeed. Delta patch below seems to do the trick.

Thanks,

        tglx

---
diff --git a/include/linux/cleanup.h b/include/linux/cleanup.h
index 6537f8dfe1bb..859b06d4ad7a 100644
--- a/include/linux/cleanup.h
+++ b/include/linux/cleanup.h
@@ -231,8 +231,7 @@ const volatile void * __must_check_fn(const volatile void *val)
  *		retain_ptr(f);
  *	return ret;
  */
-#define retain_ptr(p)				\
-	__get_and_null(p, NULL)
+#define retain_ptr(p)		((void)__get_and_null(p, NULL))
 
 /*
  * DEFINE_CLASS(name, type, exit, init, init_args...):