[open-cobol-list] Help understanding this behaviour

[Patrick]

Hi Everyone

I have attached a code snippet at the end of this email.

I don't understand the behaviour of the program.

There is an outer procedure calling in inner one. There is a linkage 
section.

In the outer program, if I create a record in the working storage 
section and pass this, everything works in the program being called.

However if I pass a string not defined in the working storage section, a 
part of a string in a paragraph from the outer program shows up later, 
the "value is spaces" no longer seems to work and an unwanted value is 
showing up later.

In hello world cobol programs there is no working storage. I am assuming 
that when we code DISPLAY "hello world" the compiler has allocated the 
memory for "hello world" but it looks like I have to create working 
storage records for everything or there will be trouble later.

So specifically with this program I have a statement:
DISPLAY "why is this string showing up later"

If I pass the variable some-str the result makes sense
./confused
some              <-- this is instruction-string

but if I pass the string "some" I get some of the string from a previous 
display statement, "why is th"
./confused
somewhy is th <-- this is instruction-string

I don't understand why this is happening, could someone help clear it up 
for me?

Thanks for reading-Patrick




       >>SOURCE FORMAT FREE
       IDENTIFICATION DIVISION.
       PROGRAM-ID. confused.
       ENVIRONMENT DIVISION.
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01 some-str PIC X(17) VALUE IS "some" .

       PROCEDURE DIVISION.

      *>this is a problem = CALL 'stack-controller' USING "some"
         CALL 'stack-controller' USING some-str
         END-CALL
       STOP RUN
       .
            100-TEST-PARA.
            DISPLAY "why is this string showing up later"
            .

*>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

             IDENTIFICATION DIVISION.
             PROGRAM-ID. stack-controller.
             ENVIRONMENT DIVISION.
             DATA DIVISION.
             WORKING-STORAGE SECTION.

             01 instruction-string PIC X(17) VALUE IS SPACES   .

             LINKAGE SECTION.
             01 instruction-argument PIC X(17)   .

             PROCEDURE DIVISION USING
                             BY VALUE instruction-argument.

             MOVE instruction-argument TO instruction-string

             DISPLAY instruction-string WITH NO ADVANCING DISPLAY " <-- 
this is instruction-string"

             EXIT PROGRAM.
             END PROGRAM stack-controller
             .


       END PROGRAM confused
       .

      *> If I pass the variable some-str the result makes sense
      *>./confused
      *>some              <-- this is instruction-string


      *> but if I pass the string "some" I get some of the string from 
the DISPLAY in 100-TEST-PARA
      *>./confused
      *> somewhy is th <-- this is instruction-string