Chapter 2: Portability Issues

This chapter describes syntax that the Net Express Compiler can flag, using warning or information error messages, as being incompatible between Net Express and COBOL for UNIX. However, the Net Express Compiler cannot flag all incompatibilities, so this chapter also describes syntax that you should manually check and change before porting the program to a UNIX system.

If a section is flagged as Not Server Express, the portability issues in that section can be ignored if you are publishing to a UNIX system that has Server Express installed.

Syntax Checking

The default for the INTLEVEL directive, for both Net Express and COBOL for UNIX, is set to 2. This is the value required to create portable intermediate code. However, certain syntax in Net Express COBOL, even when compiled with INTLEVEL"2", generates intermediate code that might not run on UNIX systems.

Therefore, if you set the WARNINGS"2" Compiler directive, the Net Express Compiler flags those syntax structures likely to cause problems if ported to a UNIX system.

Syntax Flagged

Not Server Express:

If you compile a program with the INTLEVEL"2" and WARNINGS"2" directives set on Net Express, various syntax structures are flagged. The flags are in the form of information or warning messages. You can increase the severity of an informational or warning message to a severe error using the CHANGE-MESSAGE Compiler directive. The following syntax is flagged:

Literals greater than 160 bytes. The COBOL for UNIX limit is currently 160 bytes.
Call conventions. The Net Express Compiler accepts call conventions not acceptable to the COBOL for UNIX Compiler; for example, both call conventions 256 and 512 are acceptable to Net Express, but not to COBOL for UNIX.
Filenames that contain spaces.
Entry points that each have a different call-convention specified. COBOL for UNIX assumes that the first entry point sets the call convention for the remaining entry points.
By value items greater than 4 bytes. In COBOL for UNIX, a maximum of 4 bytes can be passed by value in a CALL statement. If you try to pass a larger value it is possible that the operating system will fail.
The IS EXTERNAL DEFINITION and IS EXTERNAL REDEFINITION phrases. These are only available on Net Express.
The number of parameters on an entry point if it exceeds 255 (the maximum for COBOL for UNIX).
Multi-threading syntax. This is available in COBOL for UNIX.
Any OO COBOL support detected in a source program. OO COBOL is only supported in Object COBOL Version 4.1 for UNIX and later versions.

Syntax Not Flagged

The following syntax is not flagged, but you should check for occurrences in your programs:

Library routines that do not work on UNIX (that is, those marked in your COBOL for UNIX documentation as DOS, OS/2 or Windows only, or those that are specific to the PC.). For example, the PC_ library routines, such as PC_FIND_DRIVES, are not available in COBOL for UNIX. Some call-by-number library routines are different between Net Express and COBOL for UNIX. For example, none of the mouse routines, or controlling mouse-function using the x"AF" routine are available in UNIX.
MF_CLIENT calls, and Windows API calls are not available in UNIX.
Calls to Panels2. These are not supported.
Explicit calls to .dll files.
Filenames that do not work on UNIX; for example, those that have a .dat extension, or that contain spaces, or drive identifiers.
Embedded PC characters (that is, non-printing characters) in literals.
COMP-5 data items in the File Description. If you specify COMP-5 data items in the file record descriptions you should note that the byte-order might be different between PC and UNIX systems.
If the program contains Object Oriented syntax, then for COBOL for UNIX you should ensure that the MFOO directive is set, preferably using a $SET statement at the beginning of the source code. See the next section for details.
If the program contains arithmetic in subscripts, the source code is not portable to UNIX-based COBOL systems prior to Server Express (although the intermediate code is). The same portability issue also applies to Windows-based COBOL systems prior to Net Express and Mainframe Express.

You should also be aware of the following differences between COBOL for UNIX and Net Express COBOL:

Byte ordering. If your applications pass parameters between programs you need to be aware of the way in which systems pass parameters. Some UNIX systems have COBOL byte ordering, rather than the reverse byte ordering used by PCs. Therefore, a program that has been tested and works on a PC with an Intel chip might not work as expected when moved to, for example, a SPARC system. This issue only arises when passing parameters between COBOL and non-COBOL programs, or where the programs originating and receiving data are running on different machines.
The default filetypes differ between PCs and UNIX.
The delimiter used for line sequential files differs between PCs and UNIX.

Using the LINKCOUNT Directive

Not Server Express:

The COBOL for UNIX Compiler has a different mechanism to the Net Express Compiler for allocating storage slots for data items. Therefore, programs that work when compiled using Net Express might give the Compiler error:

0067 Please recompile using a larger value for the LINKCOUNT directive

when published to the UNIX system. If this happens you should set the LINKCOUNT directive in the program causing the error using a $SET statement in the COBOL source program.

Debugging and .idy Files

Not Server Express:

The format of .idy files is different between the Net Express and Object COBOL Development System 4.1 and earlier versions of COBOL for UNIX. Hence, you cannot use the .idy file created by Net Express on these systems.

Object-Oriented Programs

Not Server Express:

In Object COBOL for UNIX you need to specify the MFOO Compiler directive to check Class and OO programs. This directive loads the OO COBOL reserved words. Net Express accepts the MFOO directive, but ignores it, as all the OO COBOL reserved words are already loaded by default.

To develop an OO program or class under Net Express, and then recompile it using COBOL for UNIX, you need to specify the MFOO directive. This is best done by setting the directive using a $SET statement in the source code.

You should also be aware of the following:

If any user classes inherit from a class library a class with data, compilation of these user classes might fail on UNIX since the class library is different to the class library on Net Express. You are advised to inherit a class without data.
The semantics of the Class-Control paragraph was changed for Net Express. This might cause problems when recompiling with COBOL for UNIX. Class-Control entries have the following form:
```
class-control. logicalClassName is class "physicalFileName".
```
In Net Express, the logicalClassName is scoped within the individual class or program in which it exists. It has no effect beyond this. In earlier versions of OO COBOL, the logicalClassName has global scope; if entries exist for a given logicalClassName in more than one compilation unit, the entries need to match, otherwise run-time error 119 occurs.
On COBOL for UNIX, a class can have a Procedure Division outside of a method which is executed once when the class is loaded. This structure has been removed in Net Express and replaced by the Initializeclass class method. This method is invoked by the OO COBOL run-time system when the class is first loaded (it thus has a similar effect to the use of a Procedure Division in COBOL for UNIX). Initializeclass methods are therefore not automatically executed in Object COBOL for UNIX.

CGI Applications

The various versions of COBOL for UNIX provide differing levels of support for the syntax and run-time support required by CGI applications. For example, Object COBOL for UNIX introduced the ACCCGI run-time support module.

The UNIX Option provides a standard level of CGI syntax and run-time support for all COBOL for UNIX products. If the COBOL for UNIX product provides its own syntax or run-time support, this is automatically used by the UNIX Option.

Passing Java Structures to COBOL

When working with Java applications, Net Express enables you to pass data from a Java class into the Linkage Section of COBOL programs and Object COBOL methods, providing that the corresponding Java parameter is an Object which implements the mfcobol.lang.Datatype interface. If you are using Server Express version 2.0.11 or later, you can use this feature to publish from Net Express to a UNIX system: this feature is not available on earlier COBOL for UNIX systems.