offsetof(3) - NetBSD Manual Pages

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OFFSETOF(3)             NetBSD Library Functions Manual            OFFSETOF(3)

offsetof -- offset of a structure member
#include <stddef.h> size_t offsetof(type, member);
The offsetof() macro expands to an integer constant expression of type size_t and yields the offset, in bytes, of the field member from the start of the structure type. A compiler error will result if member is not aligned to a byte boundary (i.e. it is a bit-field).
Regardless of the architecture and the ABI, the following example prints the value zero for the variable x. struct example { double x; int y; char z; }; size_t x, y, z; x = offsetof(struct example, x); y = offsetof(struct example, y); z = offsetof(struct example, z); (void)printf("%zu %zu %zu\n", x, y, z);
__alignof__(3), stddef(3), typeof(3)
The offsetof() macro conforms to ANSI X3.159-1989 (``ANSI C89''). NetBSD 9.1 April 1, 2011 NetBSD 9.1
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