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From: x041sc@tamuts.tamu.edu (Sean Malloy)
Newsgroups: comp.os.msdos.programmer
Subject: Re: Memory Models in TC2.0
Message-ID: <16856@helios.TAMU.EDU>
Date: 4 Jun 91 16:36:08 GMT
References: <16854@helios.TAMU.EDU>
Sender: usenet@helios.TAMU.EDU
Organization: Texas A&M University
Lines: 54

I'm sure that this is a question that should be included in a FAQ
for this group, but I couldn't find a general FAQ in the message 
list.
 
I'm writing a (rather large) application in Turbo C 2.0 and I've
come to the point where I need to use either the Compact or Large
memory models instead of the small.  I've gone through my code and 
changed all the pointers and functions that deal with data that is
malloc()'d to be far (ie OBJECT far *draw_haxis(OBJECT far *BOX) { )
and the compiler seems to be quite happy.  No warnings; no errors.
 
(I realize that my life would be much easier using an OOL, but
my company won't buy C++ right now... ;-(.
 
The following fragment works under the small memory model, but not
under the Compact, Large, or Huge models, and I'm going nuts trying
to figure out why.  Any suggestions?
 
------------------- Begin Fragment --------------------
 
 
OBJECT far *new_object(enum obtype type) {
    OBJECT *ptr;
    coor d;
 
    d.x = 0;                 d.y = 0;
    if ((ptr = ((OBJECT far *)malloc(sizeof(OBJECT)))) == NULL ) {
       perror("New_object failed to allocate memory.  ABEND");
       exit(0);
    }
    if (obhead == NULL) { obhead = ptr;  endob =  ptr; }
    else { endob->next = ptr;    ptr->prev = endob;      endob = ptr; }
    ptr->type                    = type;
    ptr->parent                  = NULL;
    ptr->child                   = NULL;
    ptr->next                    = NULL;
 
-----------------End Fragment---------------------------------
 
...where of course OBJECT is a struct (with pointers to other 
structs, unions, etc  -- a data structure from hell)
 
My problem is that the assignment "ptr->type = type;" fails to 
change the value of ptr->type, even though malloc seems to work 
correctly  (According the integrated debugger
inside Turbo C) and my program fails because of this little
inconvience.  Do I have to declare my structs as far data items?  
If so, can someone provide me with an example - I can't seem to find
one in any of my references...
 
Thanks
 
-Sean
.