Globals in different source files

[rwskinner]

New to C so be kind please.

I have a 16 bit dos program for a microcontroller that must use the old BC5.01 compiler. I recently ran into the error during compile saying too much global data in file. So I commented out some code so it compiles and while I have a known compiling source, I'm trying to move some stuff around and recompile.

I have the following declared in my main.c

WORD  far *CustRegs;            
WORD  far *rtvals ;           
WORD  far *minvals;           
WORD  far *maxvals;            
WORD  far *avgvals;           
WORD  far *frzvals;

Then in main.c I initialize it:

 if ((rtvals   = (WORD*)farcalloc(Maxregs,sizeof(WORD)))==NULL)
  { exit(1);}
  if ((minvals  = (WORD*)farcalloc(Maxregs,sizeof(WORD)))==NULL)
  { exit(1);}
  if ((maxvals  = (WORD*)farcalloc(Maxregs,sizeof(WORD)))==NULL)
  { exit(1);}
  if ((avgvals  = (WORD*)farcalloc(Maxregs,sizeof(WORD)))==NULL)
  { exit(1);}
  if ((frzvals  = (WORD*)farcalloc(Maxregs,sizeof(WORD)))==NULL)
  { exit(1);}

Okay, first question, since these are already far, will I benefit in moving the declarations to it's own header and the init into it's own source?


How is the best way to do this so main.c can still use all these arrays?

Thanks,
Richard

[grumpy]

There is no "best". There is only a question of what you trade off to achieve what you intend.

The pointers being far makes no difference to whether there is an advantage in reorganising your source (eg what goes in source files versus headers).

What benefit are you seeking by reorganising your code?

[rwskinner]

First, I have to split my Main.c into multiple sources, so they are organized and also to reduce the compiler warning too much global data in file.

In order to do that, multiple source files will need access to those arrays that I showed.

So, how is the best way handle those arrays so they can be used in my other source files?

Can I put the items below in their own header file like this

#ifndef MBRegs_H
#define MBRegs_H 

WORD  far *CustRegs;
WORD  far *rtvals ;
WORD  far *minvals;
WORD  far *maxvals;
WORD  far *avgvals;
WORD  far *frzvals;

void Init_MBRegs(void);

#endif

Then create a source.c file and put the Init_MBRegs in it like...

#include MBRegs.h

void Init_MBRegs(void)
{
 if ((rtvals   = (WORD*)farcalloc(Maxregs,sizeof(WORD)))==NULL)  { exit(1);} 
 if ((minvals  = (WORD*)farcalloc(Maxregs,sizeof(WORD)))==NULL)  { exit(1);}
  if ((maxvals  = (WORD*)farcalloc(Maxregs,sizeof(WORD)))==NULL)  { exit(1);}
  if ((avgvals  = (WORD*)farcalloc(Maxregs,sizeof(WORD)))==NULL)  { exit(1);}
  if ((frzvals  = (WORD*)farcalloc(Maxregs,sizeof(WORD)))==NULL)  { exit(1);}
}

Will I be able to access the data in the arrays from any unit that includes the MBRegs.h?

Richard

[iMalc]

I'm not sure that moving globals into other files is going to prevent that problem. I would guess that the total amount of global data is a problem.

Does your compiler generate a map file? And do you have a map file viewer?
These show where all your global variables and static data etc go. it will help to show what is taking up the most space etc, and help show how you can rearrange things and change segment sizes etc.

[Salem]

> Will I be able to access the data in the arrays from any unit that includes the MBRegs.h?
Yes, so long as the first thing main() does is call Init_MBRegs()

The only thing you need to watch out for in the rest of the code is anywhere where you might have done sizeof(rtvals) (or any of the other arrays which are now just pointers).
If you do, you need to fix the code.

(PS - this is 20+ year old memory, most of the planet left DOS behind long ago)
Which memory model are you compiling with?
If you have compact or large, then you could just put each array definition in a separate source file, eg.

// rtvals.c
WORD rtvals[Maxregs];

Then your header file would be

extern WORD rtvals[];
// ditto for all your other arrays

In the large model for example, you're restricted to a max of 64K code/data within a single source file. But spreading things over multiple source files allows you to access multiple 64K segments in your whole program.

[rwskinner]

Thanks!
So I can initialize them all at the same time from main.c correct in InitMBRegs(), Or do they have to be initialized in their own c file?

Richard

> Will I be able to access the data in the arrays from any unit that includes the MBRegs.h?
Yes, so long as the first thing main() does is call Init_MBRegs()

The only thing you need to watch out for in the rest of the code is anywhere where you might have done sizeof(rtvals) (or any of the other arrays which are now just pointers).
If you do, you need to fix the code.

(PS - this is 20+ year old memory, most of the planet left DOS behind long ago)
Which memory model are you compiling with?
If you have compact or large, then you could just put each array definition in a separate source file, eg.

// rtvals.c
WORD rtvals[Maxregs];

Then your header file would be

extern WORD rtvals[];
// ditto for all your other arrays

In the large model for example, you're restricted to a max of 64K code/data within a single source file. But spreading things over multiple source files allows you to access multiple 64K segments in your whole program.

[nonoob]

The point is, all other source files will have header "extern ..." either by explicit mention or via #include "header...". The ONE source where you want to initialize the values should not have "extern" in front of the variables.