Linking C Programs

Specifying the Correct Entry Point

Because of the variety of ways a SAS/C program can be constructed, the same entry point is not appropriate for all programs. This section describes how to determine what entry point your application requires and then describes how to specify this entry point when you link the program.

In the case of a normal, single load module SAS/C application with no special requirements, the program entry point is the symbol MAIN . In most cases, you need not take any special action to have this entry point selected.
The module you are linking may be a dynamically loadable component of a multi-load-module program. In this case, the entry point name depends on whether you compiled with the norent option or with one of rent or rentext . In the norent case, the entry point is #DYNAMNR. In the rent or rentext case, the entry point is #DYNAMN. Under TSO, OS/390 batch and the shell, you can often specify a keyword to ensure that the correct entry point is selected.
You may have written your program to be called from assembler language, as described in Communication with Assembler Programs. Some of these calls require one of the entry points $MAINC or $MAINO, as described in this chapter. In this case, you must explicitly specify the correct entry point.
You may have compiled your initial function with the indep option. If so, this function must be specified as the entry point. Since the name of this function is not fixed, you must explicitly specify the correct entry point.
You may be linking your application with the SPE library (see Systems Programming with the SAS/C Compiler) and using the standard front-end for your environment. In this case, the correct entry point will be either #OSEP, #CMSEP, #CICSEP or #OEEP, depending on whether the program is intended for execution under OS/390, CMS, CICS, or the USS shell. Under TSO, OS/390 batch and the shell, you can often specify a keyword to ensure that the correct entry point is used.
You may be linking your application with the SPE library and using a custom front-end. In this case, you must specify your own front-end as the entry point. Since this name cannot be predicted, you must explicitly specify the entry point.

The correct entry point can always be specified via a linkage editor control card or the RESET option of the CMS LOAD command. Additionally, when you use most of

the SAS/C batch cataloged PROCs or the COOL TSO CLIST, you can often use the entry keyword to specify the entry point; when you compile under the USS shell, you can use the -Bep option of sascc370 for this. To illustrate:

OS/390 batch: // EXEC LC370L,PARM.LKED='LIST,MAP',ENTRY=MAIN
TSO: cool example(init) list map rent entry(dyn)
USS: sascc370 -Bep='#OEEP' -Tspe example/init.c

The entry keyword may have any of the following values:

MAIN The module is an ordinary C main program.

DYN The module is a rent - or rentext -compiled dynamically loadable module.

DYNNR The module is a norent -compiled dynamically loadable module

OS The module is an SPE application using the default OS/390 start-up code

OE The module is an USS SPE application using the default USS start-up code.

CSPE The module is a CICS SPE application using the default CICS start-up code. This option is available only with the CICS batch PROCs (for example, LCCCPCL).

NONE The entry point to the module is specified by an input ENTRY control statement provided by the user.

If no entry option is specified, the default is always MAIN.

Note: The -Bep option of the sascc370 shell command, unlike the entry keyword for batch and TSO, requires that the actual entry point be specified, not a code. Thus, the example above specifies -Bep='#OEEP' , not -Bep=OE . [cautionend]

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MAIN	The module is an ordinary C main program.
DYN	The module is a `rent` - or `rentext` -compiled dynamically loadable module.
DYNNR	The module is a `norent` -compiled dynamically loadable module
OS	The module is an SPE application using the default OS/390 start-up code
OE	The module is an USS SPE application using the default USS start-up code.
CSPE	The module is a CICS SPE application using the default CICS start-up code. This option is available only with the CICS batch PROCs (for example, LCCCPCL).
NONE	The entry point to the module is specified by an input ENTRY control statement provided by the user.