New subject: Sharing variables between modules

5 Sep 2002


      ...
Nick Ioffe wrote:
...
I declare public variables in module interface and then
try to use them.
The problem is that while integer variables work perfectly
all other kinds of variables (at least files and strings) 
don't work at all.
May somebody explain me what is going on?
Why integer is defined ok, but string has problem?
It's a known problem:
: the capacity of strings declared in interfaces of modules is not
: initialized (daj3.pas, sven14c.pas, nick1.pas)
Actually, it affects those types that require some automatic
initialization which are schemata (including strings), files and
objects.
It only happens with modules, not with units. I'll try to fix it
when I get to it, but it's not trivial and will require some other
cleaning up of the module mechanism ...
Frank
Hi! Thank you for all your responses. I'm sorry for bringing back
the known problem.
Here're 2 more strange behaviours with interface vs. implementation
global variables definitions. May be they will help you to find out
what is wrong in modules initialization.
Problem I:
I slightly change the previous expample - declare my_str_var in both
mod1 module interface and implementation, in mod2 implementation
and in my_main global var definitions block.
What happens is that although each variable should be local for the module
(at least that is what the common sense tells me) all the variables
behave like there're the same variable.
I've checked it with debugger and it points to the same address in all modules.
the source is as follows:
---------------mod1.pas-------------------
module mod1 interface;
export mod1 = all;
Type
    mystr = string(7);
Var
    my_str_var : mystr;
procedure mSet (str_arg : mystr);
end.
module mod1 implementation;
Var
    my_str_var : mystr;
procedure mSet (str_arg : mystr);
begin
   writeln ('mod1 mset str_arg:',str_arg,'.');
   my_str_var := str_arg;
   writeln ('mod1 mset my_str_var:',my_str_var,'.');
end;
end.
---------------mod2.pas--------------------
module mod2 interface
export mod2 = all;
import mod1;
procedure sSet (str_arg : mystr);
function sGet : mystr;
end.
module mod2 implementation;
import mod1
Var
    my_str_var : mystr;
procedure sSet (str_arg : mystr);
begin
   writeln ('mod2 sset str_arg:',str_arg,'.');
   my_str_var := str_arg;
   writeln ('mod2 sset my_str_var:',my_str_var,'.');
end;
function sGet : mystr;
begin
   sGet := my_str_var;
end;
end.
-----------------------my_main.pas-------------------
program my_main (input,output);
import mod1;
import mod2;
Var
   another_str : mystr := '7654321';
   my_str_var  : mystr;
begin
   sSet ('0123456');
   writeln ('1. my_main another_str:',another_str,'.');
   another_str := sGet;
   writeln ('2. my_main another_str:',another_str,'.');
my_Str_var := 'abcdefg';
   another_str := sGet;
   writeln ('2. my_main another_str:',another_str,'.');
mSet ('nick io');
   another_str := sGet;
   writeln ('2. my_main another_str:',another_str,'.');
end.
--------------------------------------------------------
The run results are:
mod2 sset str_arg:0123456.
mod2 sset my_str_var:0123456.
1. my_main another_str:7654321.
2. my_main another_str:0123456.
3. my_main another_str:abcdefg.
mod2 sset str_arg:nick io.
mod2 sset my_str_var:nick io.
4. my_main another_str:nick io.
=============================================================
Problem II.
As we've seen in problem I repeating the declaration in module
implementation solves the problem of accessing the strings.
Now I need to declare the array of string:
-----------------mod3_1.pas-------------------------
module mod3 interface;
export mod3 = all;
Var
    my_buff : array [1..10] of String(80);
procedure pBuff;
end.
module mod3 implementation;
Var
    my_buff : array [1..10] of String(80);
procedure pbuff;
var	int ii;
begin
    for ii:=1 to 10 do
    	writeln (my_buff[ii]);
end;
end.
------------------------------------------------
When I compile it I get the following errors:
mod3.pas:15: redeclaration of 'My_buff'
mod3.pas:10: previous declaration of 'Mybuff'
then I change the source as follows:
-----------------mod3_2.pas-------------------------
module mod3 interface;
export mod3 = all;
Type
    my_buff_type = array [1..10] of String(80);
Var
    my_buff : my_buff_type;
procedure pBuff;
end.
module mod3 implementation;
Var
    my_buff : my_buff_type;
procedure pbuff;
var	int ii;
begin
    for ii:=1 to 10 do
    	writeln (my_buff[ii]);
end;
end.
------------------------------------------------
Now everything compiles good.
Why? What is the difference?
Sincerely, 
Nick

Re: Sharing variables between modules