IBM AS/400 manual Call Operations, Using, V4R4M0, Fixed-Form Call

Using

the

Fixed-Form Call

Operations

For ILE C, declare the

returned

value as a struct with a

subfiel

(The RPG return value can also

be

declared

as

a

3-digit

unsigned

since that is the way

that

ILE

C

defines

a

1-byte character.)

typedef struct

{

char c;

} RPGCHAR;

RPGCHAR RPGPROC(int i);

void fn()

{

RPGCHAR ret;

ret = RPGPROC(3);

/* The returned character is ret.c */

}

2. When

passing

parameters

by

value to or

from

ILE

C

of

the

followin

¹

1-byte character

¹

2-byte

integer

or

unsigned

integer

¹

4-byte float

you may get incorrect results since ILE C assumes

that

these

para

widened

to

4-byte integer or

unsigned

integer

or to 8-byte

float.

To

correct

this

problem

you

can specify in your ILE C code that

should

not

occur,

or

you

can

declare the parameters in RPG

in

the

form. It is straightforward to correct short integers and short f

defining

the

parameters

as 4-byte integer

or

8-byte

float,

but

to

1-byte

character

values

is

more

difficult.

The

following

illustrates

handle

this:

* This prototype and call might give incorrect results

D proc

PR

D

char1

1A

VALUE

C

CALLP

proc(character_parm)

* Code this instead

D proc

PR

D

char1

10U 0 VALUE

D cvtchar1

DS

D

cvtuns10

10U 0 INZ(0)

D

cvtchar1

1A

OVERLAY(cvtuns10:4)

C

EVAL

cvtchar1 = character_parm

C

CALLP

proc(cvtuns10)

3. Using

ILE

C

and

other languages, you can declare pointers to ter

memory. ILE C requires a special compile-time option to address thi

storage,

but

ILE

RPG

can

always

address this storage if compiled

release

of

V4R4M0

or

later.

For

more

information

on pointers

in

tera

theILE Concepts, SC41-5606-03 publication.

Using

the

Fixed-Form

Call Operations

You

use

the

CALL

(Call

a

Program)

operation

to

make

a

program

call

and

t

CALLB

(Call a Bound Procedure) operation to make a procedure call to pr

or

procedures

that

are

not

prototyped. The two call operations are v

their syntax and their use. To

call

a

program

or

procedure,

follow

th

steps:

1. Identify

the

object

to

be

called

in

the

Factor

2

entry.

148 ILE RPG for AS/400 Programmer's Guide