Re: [PATCH v5 3/4] cleanup: Annotate guard constructors with nonnull

[Dmitry Ilvokhin]

On Fri, Jun 05, 2026 at 08:46:57AM +0300, Dan Carpenter wrote:
> On Tue, Jun 02, 2026 at 07:12:52AM +0000, Dmitry Ilvokhin wrote:
> > Add __nonnull_args() to unconditional guard constructors so the compiler
> > warns when NULL is statically known to be passed:
> > 
> > - DEFINE_GUARD(): re-declare the constructor with __nonnull_args().
> > - __DEFINE_LOCK_GUARD_1(): annotate the constructor directly.
> > 
> > DEFINE_LOCK_GUARD_0() needs no annotation: its constructor takes no
> > pointer arguments (.lock is hardcoded to (void *)1).
> > 
> > Define the __nonnull_args() macro in compiler_attributes.h, following
> > the existing convention for attribute wrappers. Deliberately not named
> > '__nonnull', to avoid clashing with glibc's __nonnull() when kernel and
> > userspace headers are combined (User Mode Linux for example).
> > 
> > Signed-off-by: Dmitry Ilvokhin <d@xxxxxxxxxxxx>
> > ---
> > Miguel, I dropped your Acked-by due to the rename. Went with
> > __nonnull_args() (over __knonnull()). Happy to restore your tag if that
> > spelling works for you.
> > 
> 
> Sparse doesn't like an empty __nonnull_args() at all.
> 
> ./include/linux/spinlock.h:608:1: error: an expression is expected before ')'
> ./include/linux/spinlock.h:619:1: error: an expression is expected before ')'
> ./include/linux/spinlock.h:631:1: error: an expression is expected before ')'
> 
> Shouldn't we specify the arguments which are non-NULL?
> __nonnull_args(1)?

Thanks for the report, Dan.

That is interesting, it seems sparse trips over the empty-parens form
the guard macro expands to, nonnull(), but is fine with
__attribute__((nonnull)) without explicit arguments, that a few places
in-tree already use. GCC and clang accept both, so this probably
deserves a fix in sparse too.

Meanwhile, spelling the argument out explicitly is a simple and
reasonable fix (and arguably clearer). Patch below.