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From: Dave.Harris@f14.n15.z1.fidonet.org (Dave Harris)
Newsgroups: comp.lang.c
Subject: Help needed with: sizeof (struct a)
Message-ID: <14693.286362FE@stjhmc.fidonet.org>
Date: 22 Jun 91 14:40:55 GMT
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Organization: FidoNet node 1:15/14 - Nibbles 'n Bits, Orem UT
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In a message of <Jun 20 21:49>, Dave Corcoran (1:114/15) writes: 

 >My Sun cc prints 4 for both structs, prints 3 for the array

 >-----------------8<-------------------- 
 >struct a {char x;char y;char z};
 >struct b {char x[3]};
 >char c[3];
 >main()
 >{
 >        printf("%d\n",sizeof (struct a));
 >        printf("%d\n",sizeof (struct b));
 >        printf("%d\n",sizeof c);
 >}
 >-----------------8<--------------------

 >Is there any way to cause cc to force sizeof return the actual size of 
 >the
 >structs without rounding up to the next highest sizeof (short)?
 >Thanx

I assume that you are getting 4 when expecting 3?
If so...

Normally, 4 IS the size of this struct when it is stored in memory.  Why you 
would want 3 returned escapes me.  You use the 3 to malloc() (or any number of 
other address calculations and), you are just asking for bugs.  

There might be some options that allow you to specify alignment on a byte 
boundary as opposed to a word boundary.  This will cost you some speed 
however.

Dave Harris 


 

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