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libext2fs: use statement-expression for container_of only on GNU-compatible compilers

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Functionally, the statement-expression is not necessary here; it
just gives a bit of type-safety to make sure the pointer really
does have a compatible type with the specified member of the struct.

When statement expressions are not available, we can just use a
portable fallback macro that skips this member type check.

Signed-off-by: Michael Forney <mforney@mforney.org>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Michael Forney 2021-04-14 00:41:27 -07:00 committed by Theodore Ts'o
parent f11448318f
commit 9d5fdcc5db
1 changed files with 5 additions and 0 deletions
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5
lib/ext2fs/compiler.h
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@ -14,9 +14,14 @@
#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
#endif
#ifdef __GNUC__
#define container_of(ptr, type, member) ({ \
const __typeof__( ((type *)0)->member ) *__mptr = (ptr); \
(type *)( (char *)__mptr - offsetof(type,member) );})
#else
#define container_of(ptr, type, member) \
((type *)((char *)(ptr) - offsetof(type, member)))
#endif
#endif /* _EXT2FS_COMPILER_H */