offsetof.gml

来自「开放源码的编译器open watcom 1.6.0版的源代码」· GML 代码 · 共 52 行

.func offsetof
#include <stddef.h>
size_t offsetof( composite, name );
.funcend
.desc begin
The &func macro returns the offset of the element
.arg name
within the
.kw struct
or
.kw union
.arg composite.
This provides a portable method to determine the offset.
.desc end
.return begin
The &func function returns the offset of
.arg name.
.return end
.exmp begin
#include <stdio.h>
#include <stddef.h>

struct new_def
{  char *first;
   char second[10];
   int third;
};

void main()
  {
    printf( "first:%d second:%d third:%d\n",
        offsetof( struct new_def, first ),
        offsetof( struct new_def, second ),
        offsetof( struct new_def, third ) );
  }
.exmp output
.blktext begin
In a small data model, the following would result:
.blktext end
.blkcode begin
first:0 second:2 third:12
.blkcode end
.blktext begin
In a large data model, the following would result:
.blktext end
.blkcode begin
first:0 second:4 third:14
.blkcode end
.exmp end
.class ANSI
.system