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want the offset address of a variable

Posted on 2004-09-28
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Last Modified: 2010-04-01
Im new to c++ and I want a function that returns the offset address of a variable.........Im using the API functions.
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Question by:ewak
6 Comments
 
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by:
rstaveley earned 500 total points
ID: 12168112
Use the & operator.

e.g.

  int i = 123;
  cout << "Address of i is " << &i << '\n';
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by:Axter
Axter earned 500 total points
ID: 12168259
To add to above comment:

int * GetOffSet(int& src){
     return &src;
}
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by:grg99
grg99 earned 500 total points
ID: 12168526
Could you explain what you mean by the "offset" address?

"Offset" is usually a concept related to the old 16-bit segment model.  

Most of us nowadays use the 32-bit flat model.

One rarely needs the "offset" in this more enlightened era.

Pls explain.

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Assisted Solution

by:jkr
jkr earned 500 total points
ID: 12169657
Are you thinking about 'offsetof()'?

#define offsetof(s,m)   (size_t)&(((s *)0)->m)

E.g.

struct tm {
        int tm_sec;     /* seconds after the minute - [0,59] */
        int tm_min;     /* minutes after the hour - [0,59] */
        int tm_hour;    /* hours since midnight - [0,23] */
        int tm_mday;    /* day of the month - [1,31] */
        int tm_mon;     /* months since January - [0,11] */
        int tm_year;    /* years since 1900 */
        int tm_wday;    /* days since Sunday - [0,6] */
        int tm_yday;    /* days since January 1 - [0,365] */
        int tm_isdst;   /* daylight savings time flag */
        };

struct tm mytm;

printf ( "Address offset of 'tm_mon' in 'struct tm' is %d\n", offsetof ( &mytm, tm_day));
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Expert Comment

by:Axter
ID: 12661379
>>Any objections should be posted here in the next 4 days. After that time, the question will be closed.

I recommend splitting the points to all four experts {rstaveley, Axter,  grg99, & jkr}

All four experts help give a full answer.
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Expert Comment

by:rstaveley
ID: 12662452
Agreed wih Axter
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