From: eplmst AT lu DOT erisoft DOT se (Martin Stromberg)
Newsgroups: alt.comp.lang.learn.c-c++,comp.lang.c++,comp.os.msdos.djgpp
Subject: Re: Holes in structure
Followup-To: alt.comp.lang.learn.c-c++,comp.lang.c++,comp.os.msdos.djgpp
Date: 6 Nov 2001 13:03:57 GMT
Organization: Ericsson Erisoft AB, Sweden
Lines: 69
Message-ID: <9s8n3t$t2b$1@antares.lu.erisoft.se>
References: <3BE7D280 DOT C1732E58 AT bigfoot DOT com>
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To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp
Reply-To: djgpp AT delorie DOT com

Alex Vinokur (alexvn AT bigfoot DOT com) wrote:
: ===============================================================
: Windows98
: gpp : GNU C++ version 2.95.3 20010315/djgpp (release) (djgpp)
:       compiled by GNU C version 2.95.3 20010315/djgpp (release).
: ===============================================================
: //-----------
: struct type1
: {
:   long   item1;
:   char   item2;
:   short  item3;
:   char   item4;
:   long   item5;
:   long   item6;
:   int    item7;
:   short  item8;
:   short  item9;
:   char   item10;
:   char   item11;
:   long   item12;
:   float  item13;
:   double item14;
:   char   item15;
: };

: #########################################################
: ############### Running (log file) : BEGIN ##############

: %a.exe

: type1.item1  (long)   -> Address = 0   : sizeof = 4 : No hole
: type1.item2  (char)   -> Address = 4   : sizeof = 1 : No hole
: type1.item3  (short)  -> Address = 6   : sizeof = 2 : Hole = 1 (before
: item)
: type1.item4  (char)   -> Address = 8   : sizeof = 1 : No hole
: type1.item5  (long)   -> Address = 12  : sizeof = 4 : Hole = 3 (before
: item)
: type1.item6  (long)   -> Address = 16  : sizeof = 4 : No hole
: type1.item7  (int)    -> Address = 20  : sizeof = 4 : No hole
: type1.item8  (short)  -> Address = 24  : sizeof = 2 : No hole
: type1.item9  (short)  -> Address = 26  : sizeof = 2 : No hole
: type1.item10 (char)   -> Address = 28  : sizeof = 1 : No hole
: type1.item11 (char)   -> Address = 29  : sizeof = 1 : No hole
: type1.item12 (long)   -> Address = 32  : sizeof = 4 : Hole = 2 (before
: item)
: type1.item13 (float)  -> Address = 36  : sizeof = 4 : No hole
: type1.item14 (double) -> Address = 40  : sizeof = 8 : No hole
: type1.item15 (char)   -> Address = 48  : sizeof = 1 : No hole

: Struct type1 :
:  sizeof   = 52
:  All items sum  = 43
:  Diff (52 - 43)  = 9
:  All holes sum  = 6


:  2. struct type1 :
:            Why is not 'Diff' (between 'sizeof' and 'All items sum')
:   equal 'All holes sum' ?
:      Note. 'Diff' = 9, 'All holes sum' = 6.
:     Where has 3 bytes ('Diff' - 'All holes sum') gone?

It's padding after item15 I guess.


Right,

						MartinS