Subj : Sqfix problem
To   : Bo Simonsen
From : Bob Jones
Date : Sun Oct 05 2003 07:42 am

 BS>> Of some reason sizeof(XMSG) doesn't give the exact
 BS>> size, the problem did Squish also have but i fixed it
 BS>> there, but #define'ing XMSG_SIZE in msgapi, it was
 BS>> right after the porting of maximus..

 BJ> Ah....  That would explain it.....  Yes, sizeof(<STRUCTURE>) may not
 BJ> work in all environments now.....  :(

 BS> Well I just don't understand it, because it does 
 BS> normally work under Linux, maybe it's the arrays..

The problem is that sizeof(<STRUCTURE>) returns the number of bytes in memory.  
By default, structures are not packed.  If the structure was packed, then 
sizeof(<STRUCTURE>) should have worked for reading and writing files.  Wes has 
a define made to allow packing the structures under GCC but not on other 
compilers where the packing isn't needed.  Any structure that has more than one 
item (which it should or you wouldn't have used a structure), and has elements 
that are not an exact multiple of 4 or 8 bytes may get located on 4 (or 8) byte 
boundaries, resulting in unused bytes in the structures memory immage.  So, 
sizeof(<STRUCTURE>) is needed for memory copies, but fail when reading and/or 
writing binary files in these cases.....

Take care.....

Bob Jones, 1:343/41


--- Maximus/2 3.01
 * Origin: Top Hat 2 BBS (1:343/41)

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