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Sync flexmember.h with gnulib

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It sync with gnulib commit 43ee1a6bf.
This commit is contained in:
Adhemerval Zanella 2020-12-30 16:14:58 -03:00
parent 11b2858bd1
commit 9c774ad764
1 changed files with 20 additions and 5 deletions
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25
posix/flexmember.h
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@ -33,11 +33,26 @@
# define FLEXALIGNOF(type) _Alignof (type)
#endif
/* Upper bound on the size of a struct of type TYPE with a flexible
array member named MEMBER that is followed by N bytes of other data.
This is not simply sizeof (TYPE) + N, since it may require
alignment on unusually picky C11 platforms, and
FLEXIBLE_ARRAY_MEMBER may be 1 on pre-C11 platforms.
/* Yield a properly aligned upper bound on the size of a struct of
type TYPE with a flexible array member named MEMBER that is
followed by N bytes of other data. The result is suitable as an
argument to malloc. For example:
struct s { int n; char d[FLEXIBLE_ARRAY_MEMBER]; };
struct s *p = malloc (FLEXSIZEOF (struct s, d, n * sizeof (char)));
FLEXSIZEOF (TYPE, MEMBER, N) is not simply (sizeof (TYPE) + N),
since FLEXIBLE_ARRAY_MEMBER may be 1 on pre-C11 platforms. Nor is
it simply (offsetof (TYPE, MEMBER) + N), as that might yield a size
that causes malloc to yield a pointer that is not properly aligned
for TYPE; for example, if sizeof (int) == alignof (int) == 4,
malloc (offsetof (struct s, d) + 3 * sizeof (char)) is equivalent
to malloc (7) and might yield a pointer that is not a multiple of 4
(which means the pointer is not properly aligned for struct s),
whereas malloc (FLEXSIZEOF (struct s, d, 3 * sizeof (char))) is
equivalent to malloc (8) and must yield a pointer that is a
multiple of 4.
Yield a value less than N if and only if arithmetic overflow occurs. */
#define FLEXSIZEOF(type, member, n) \