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Message-Id: <20220210170434.3924169-1-dmitry.baryshkov@linaro.org>
Date: Thu, 10 Feb 2022 20:04:34 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: linux-kernel@...r.kernel.org,
Andrew Morton <akpm@...ux-foundation.org>
Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: [PATCH] container_of.h: make container_of const-aware
container_of() macro has one major drawback. It does not check whether
the passed ptr has a const pointer, the result will always be a
non-const pointer. Use a _Generic() construct (supported since gcc 4.9
and Clang 3.0) to teach container_of that if converting a const pointer,
the returned pointer should also have the const modifier.
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
---
include/linux/container_of.h | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/include/linux/container_of.h b/include/linux/container_of.h
index 2f4944b791b8..269f64e27b09 100644
--- a/include/linux/container_of.h
+++ b/include/linux/container_of.h
@@ -19,7 +19,11 @@
static_assert(__same_type(*(ptr), ((type *)0)->member) || \
__same_type(*(ptr), void), \
"pointer type mismatch in container_of()"); \
- ((type *)(__mptr - offsetof(type, member))); })
+ _Generic((ptr), \
+ const typeof(((type *)0)->member)*: \
+ ((const type *)(__mptr - offsetof(type, member))), \
+ default: ((type *)(__mptr - offsetof(type, member))) \
+ ); })
/**
* container_of_safe - cast a member of a structure out to the containing structure
@@ -35,6 +39,10 @@
__same_type(*(ptr), void), \
"pointer type mismatch in container_of_safe()"); \
IS_ERR_OR_NULL(__mptr) ? ERR_CAST(__mptr) : \
- ((type *)(__mptr - offsetof(type, member))); })
+ _Generic((ptr), \
+ const typeof(((type *)0)->member)*: \
+ ((const type *)(__mptr - offsetof(type, member))), \
+ default: ((type *)(__mptr - offsetof(type, member))) \
+ ); })
#endif /* _LINUX_CONTAINER_OF_H */
--
2.34.1
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