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Holes in records

Posted on 2000-04-27
Last Modified: 2010-04-04
How can I avoid a hole in the memory when defining a record?

var x: record
a: byte;
b: word;
c: byte;

here is the sizeOf(x) = 6
I want it to be 4, so no memory holes between the bytes and the word!
Question by:barzangy

Expert Comment

ID: 2754826
By default there is no holes between record fields, even if you define an array of records there is no holes btween each record and the another one


Accepted Solution

AttarSoftware earned 50 total points
ID: 2754830
Does the packed keyword do this?


var x : packed record

I might not have the syntax right, but the help files should help with this...

LVL 10

Expert Comment

ID: 2754843
Tim is right. The "holes" are there to align members of the record at a particular boundary to inrease access speed. In order to avoid record alignment use:

  x: packed record
    a: byte;
    b: word;
    c: byte;

Ciao, Mike

Expert Comment

ID: 2754866
Beyond declaring a record as packed, you have a compiler option for record field alignment $A+/-.  This is from the help file:

The $A directive controls alignment of fields in record types.
In the {$A+} state, fields in record types that are declared without the packed modifier are aligned. In the {$A-} state, fields in record types are never aligned. Record type field alignment is described in the Object Pascal Language Guide.
Regardless of the state of the $A directive, variables and typed constants are always aligned for optimal access. In the {$A+} state, execution will be faster.

In your case, however, use packed, which will override this.

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