The patch titled
Subject: container_of.h: make container_of const-aware
has been added to the -mm tree. Its filename is
container_ofh-make-container_of-const-aware.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/container_ofh-make-container_of-const-aware.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/container_ofh-make-container_of-const-aware.patch
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------------------------------------------------------
From: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
Subject: 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.
Link: https://lkml.kernel.org/r/20220210170434.3924169-1-dmitry.baryshkov@xxxxxxxxxx
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/include/linux/container_of.h~container_ofh-make-container_of-const-aware
+++ a/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 */
_
Patches currently in -mm which might be from dmitry.baryshkov@xxxxxxxxxx are
container_ofh-make-container_of-const-aware.patch
