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[open-cobol-list] Re: static cobol 2 c

From: Roger While
Subject: [open-cobol-list] Re: static cobol 2 c
Date: Tue Oct 25 00:26:57 2005

> what about float/double numbers ?

COMP-1 (AKA FLOAT-SHORT) is always "native" - 4 bytes (float)
COMP-2 (AKA FLOAT-LONG)   is always "native" - 8 bytes (double)

Also, a word of warning about alignment :

If you want to pass a group item as a "C structure" (and reference it as such -
ie. struct mystruct * ),
make sure that the group item is a 01 level.
Why ? - On i386 and "alignment tolerant" architectures you can get away with
casting anything to anything. On other boxes this is definitely not so.

Further, if we take your example :
> typedef struct abcd {
>        char phrase[10];
>        int compteur ;
> } efgh;
and assuming (as previously said) that we have used the "pack" attribute,
then the 4 byte "compteur" field is not naturally aligned.
Once again, on alignment tolerant machines, you get away with this.
On non-alignment tolerant architectures, you will get a bus error when
you access compteur.
(unless GCC is clever enough to sort this out - Anybody know ?)

Note that all of this thread also applies to MF and ACU Cobol.

The absolute correct and poratable way to communicate with C is
to assume everything is characters eg.
int my_c_routine ( char * mygrouppointer )
        struct {
                char            phrase[10];
                char            compteur[4];
        } mystruct;
        int                     mylocalcompteur;

        /* Note we must use 14 and not "sizeof" here */
        (void)memcpy ((char *)&mystruct, mygrouppointer, 14);
        (void)memcpy ((char *)&mylocalcompteur, mystruct.compteur, sizeof(int));

And, if that isn't enough, be aware of fields that have "USAGE POINTER" -
These are 4 bytes on 32-bit boxes and 8 bytes on 64-bit boxes.
So, you would need something like this for POINTER items :
      03  MYALPHA      PIC X(10).

#define MY_POINTER_LENGTH       sizeof(char *)
int my_c_routine ( char * mygrouppointer )
        struct {
                char            phrase[10];
                char            mypointer[MY_POINTER_LENGTH];
        } mystruct;
        char *                  mylocalpointer;

        /* Note we must use 10 + .. and not "sizeof" here */
        (void)memcpy ((char *)&mystruct, mygrouppointer, 10 + 
        (void)memcpy ((char *)&mylocalpointer, mystruct.mypointer, 


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