[Info-vax] VAX BASIC global variables.

[E Thump]

On Friday, October 15, 2021 at 4:44:49 PM UTC+1, Jeffrey H. Coffield wrote:
> On 10/15/2021 02:42 AM, E Thump wrote: 
> 
> > 
> > Here's what I've done now: 
> > 
> > External SUB adder (integer,integer) 
> > External INTEGER a,b 
> > 
> > a=100 
> > b=200 
> > 
> > print "a+b before sub: ",a+b 
> > call adder (10,20) 
> > print "a+b after sub: ",a+b 
> > 
> > end program 
> > 
> > sub adder (integer c,integer d) 
> > a=400 
> > b=1000 
> > print "a+b in sub: ",a+b 
> > print "c+d in sub: ",c+d 
> > end sub 
> > 
> > compiles clean but throws this when linking : 
> > 
> > %LINK-W-NUDFSYMS, 2 undefined symbols: 
> > %LINK-I-UDFSYM, A 
> > %LINK-I-UDFSYM, B 
> > %LINK-W-USEUNDEF, undefined symbol A referenced 
> > in psect $CODE offset %X00000021 
> > in module TEST$MAIN file SYS$USERS:[ECKY]TEST.OBJ;24 
> > %LINK-W-USEUNDEF, undefined symbol B referenced 
> > in psect $CODE offset %X0000002C 
> > in module TEST$MAIN file SYS$USERS:[ECKY]TEST.OBJ;24 
> > %LINK-W-USEUNDEF, undefined symbol A referenced 
> > in psect $CODE offset %X00000048 
> > in module TEST$MAIN file SYS$USERS:[ECKY]TEST.OBJ;24 
> > ...... 
> > 
> >
> The EXTERNAL statement says something else will define whatever you are 
> referencing. COMMON or MAP is what you want and it has to be in all 
> program/subprogram sections. The "MY_DATA" will be the name that is 
> shared so it can be whatever you want, it just has to be the same in all 
> sections that want to reference it. 
> Try this: 
> ---------------------------------------- 
> 
> External SUB adder (integer,integer) 
> COMMON (MY_DATA) INTEGER a,b
> a=100 
> b=200 
> 
> print "a+b before sub: ",a+b 
> call adder (10,20) 
> print "a+b after sub: ",a+b 
> 
> end program 
> 
> sub adder (integer c,integer d)
> COMMON (MY_DATA) INTEGER a,b
> a=400 
> b=1000 
> print "a+b in sub: ",a+b 
> print "c+d in sub: ",c+d 
> end sub
> ------------------------------------------ 
> Jeff Coffield 
> www.digitalsynergyinc.com

Cheers, yeah I went back to Arne's initial suggestion and am backfilling my program accordingly.

Next question to do with arrays. Instead of doing DIM Z(10) it seems I should do COMMON (MY_DATA) INTEGER Z(10) and then use that exact same line within the sub. The 10 and everything has to match. Am I on the right lines there?

Appreciate the help guys!