[Info-vax] VAX BASIC global variables.

[Jeffrey H. Coffield]

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