Package: manpages-dev
Version: 2.28-1
Severity: wishlist
Tags: patch
Included is a manpage documenting the offsetof() macro; please
consider including it.
.\" Copyright (C) 2006 Justin Pryzby <[EMAIL PROTECTED]>
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.\" References:
.\" /usr/lib/gcc/i486-linux-gnu/4.1.1/include/stddef.h
.\" glibc-doc
.TH ERROR 3 "2006-05-23" GNU
.SH NAME
offsetof \- offset of a structure member
.SH SYNOPSIS
\fB#include <stddef.h>
\fBsize_t offsetof(\fItype\fP, \fPmember\fP);
.SH DESCRIPTION
\fBoffsetof\fP() is a macro provided to compute the offset of a given
element within a structure. The ordering within memory of a C
structure is undefined, as is its size; compilers are allowed to
reorder and pad structures. An element's offset is not necessarily
given by the sum of the sizes of the previous elements' sizes; use
\fBoffsetof\fP() instead.
.SH "RETURN VALUE"
\fBoffsetof\fP() returns the offset of the given element within the
given datatype, in units of bytes.
.SH EXAMPLE PROGRAM
.nf
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
int main()
{
struct a {
int i;
char c;
double d;
};
/* Output is compiler-dependant */
printf("%d\n", offsetof(struct a, c));
exit(EXIT_SUCCESS);
}
.fi
.SH NOTES
\fBoffsetof\fP can be implemented as:
.sp
.nf
\fB#define offsetof(\fItype\fP, \fPmember\fP) \\
\fB&((type *)0)->\fImember\fP - (char *)((\fPtype\fP *)0)
.fi
.SH "CONFORMING TO"
\fBoffsetof\fP() is a POSIX requirement.
.\" .SH SEE ALSO
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