From:	Luke Lee <comforth AT ms2 DOT hinet DOT net>
Newsgroups:	comp.os.msdos.djgpp
Subject:	#pragma pack(1) and <grx20.h> ?
Date:	Fri, 14 Feb 1997 15:21:20 +0800
Organization:	Common Forth Labortory
Lines:	50
Message-ID:	<33041270.30ED@ms2.hinet.net>
Reply-To:	comforth AT ms2 DOT hinet DOT net
NNTP-Posting-Host:	@140.109.249.6
Mime-Version:	1.0
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

Hi, there :
    I'm just wondering whether it works or not if :

    #pragma pack(1);
    #include <grx20.h>

    I've test the following data structure with/without #pargma pack(1);

     struct _GR_videoModeExt {
         enum   _GR_frameModes   mode;
         struct _GR_frameDriver *drv;
         char    far *frame;
         char    cprec[3];
	 char    cpos[3];
	 int     flags;
    	 int   (*setup)(GrVideoMode *md,int noclear);
   	 int   (*setvsize)(GrVideoMode *md,int w,int h,GrVideoMode *result);
    	 int   (*scroll)(GrVideoMode *md,int x,int y,int result[2]);
    	 void  (*setbank)(int bk);
    	 void  (*setrwbanks)(int rb,int wb);
    	 void  (*loadcolor)(int c,int r,int g,int b);
     };

   I use the following line to show the difference :

   printf("sizeof(cprec+cpos)=%d\n",
          (unsigned)(&st.flags)-(unsigned)(&st.cprec[0]));

 * With #pragma pack(1); 
     sizeof(cprec+cpos)=6  
 * Without #pragma pack(1);
     sizeof(cprec+cpos)=8

   Such a problem should occurred in many places, such as read/write
data files,
   linking CodeBase...etc

   My question is this : 
   1. Is there a chance that I might link my code with "libgrx20.a" with
this 
      different #pragma ?
   2. If the offset of each field is important, should I rebuild EACH
LIBRARY
      with different #pragma setting ????!!!!
   3. Or, there is a gcc command line option for this ?

 Sorry if this is a dumb question... :-P
 since this problem is critical to my program ... Thanks !

   Luke

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