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From: kaiser@ananke.stgt.sub.org (Andreas Kaiser)
Newsgroups: comp.lang.c
Subject: Structure and Array equivalence
Message-ID: <7.26F4ED23@ananke.stgt.sub.org>
Date: 16 Sep 90 07:47:10 GMT
Organization: Ananke, Stuttgart, FRG
Lines: 40

In a message of <Sep 15 00:20>, Dave Lee (dave@dptechno.uucp ) writes: 

 DL> struct  A_STRUCT {
 DL>         TYPE    T1,T2,T3,T4,T5 .... TN;
 DL> } A ;

 DL> funcA( X )
 DL> A_STRUCT *X;
 DL> {
 DL>         X->T3 =  C;
 DL> }

 DL> funcB( X )
 DL> TYPE *X;
 DL> {
 DL>         X[2] = C ;
 DL> }

 DL>         If you have a structure which contains members of only one type,
 DL> and you have an array of the same type with the same number of elements,
 DL> is the compiler guarenteed to place the members in the same offsets in
 DL> both the array and structure ?

There is no guarantee that the any alignment padding is the same within 
structures and arrays. There is no guarantee for any kind of alignment anyway.

 DL> Q:      Are funcA() and funcB() GUARENTEED to do the same thing ?

No.

                Gruss, Andreas

 
 
 

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