linux-kernel - [RFC v2 1/4] cleanup: Fix discarded const warning when defining guards

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Date: Thu, 25 Jan 2024 15:57:20 -0800
From: Vinicius Costa Gomes <vinicius.gomes@...el.com>
To: brauner@...nel.org,
	amir73il@...il.com,
	hu1.chen@...el.com
Cc: miklos@...redi.hu,
	malini.bhandaru@...el.com,
	tim.c.chen@...el.com,
	mikko.ylinen@...el.com,
	lizhen.you@...el.com,
	linux-unionfs@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Vinicius Costa Gomes <vinicius.gomes@...el.com>
Subject: [RFC v2 1/4] cleanup: Fix discarded const warning when defining guards

When defining guards for const types the void* return implicitly
discards the const modifier. Be explicit about it.

Compiler warning (gcc 13.2.1):

/include/linux/cleanup.h:154:18: warning: return discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
  154 |         { return *_T; }
      |                  ^~~
/include/linux/cred.h:193:1: note: in expansion of macro ‘DEFINE_GUARD’
  193 | DEFINE_GUARD(cred, const struct cred *, _T = override_creds_light(_T),
      | ^~~~~~~~~~~~

Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@...el.com>
---
 include/linux/cleanup.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/cleanup.h b/include/linux/cleanup.h
index c2d09bc4f976..ac521c4521cd 100644
--- a/include/linux/cleanup.h
+++ b/include/linux/cleanup.h
@@ -151,7 +151,7 @@ static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \
 #define DEFINE_GUARD(_name, _type, _lock, _unlock) \
 	DEFINE_CLASS(_name, _type, if (_T) { _unlock; }, ({ _lock; _T; }), _type _T); \
 	static inline void * class_##_name##_lock_ptr(class_##_name##_t *_T) \
-	{ return *_T; }
+	{ return (void *)*_T; }
 
 #define DEFINE_GUARD_COND(_name, _ext, _condlock) \
 	EXTEND_CLASS(_name, _ext, \
-- 
2.43.0