NetWare Loadable Module Programming HOWTO

3. First Step: Hello world

As usual, we will start with the famous "Hello world" program. The source code for hello.nlm is available in the nlm-samples package. You can download it from ftp://ftp.penguin.cz/pub/users/mhi/nlm/.

3.1 hello.c - Source File

#define N_PLAT_NLM                                /* Define dest. platform */

#include <nwconio.h>                              /* ConsolePrintf */

int
main (int argc, char **argv)
{
  int i;

  ConsolePrintf ("\rHello world!\n\n");           /* print on system console */

  ConsolePrintf("Arguments:\n");                  /* all arguments */
  for (i=0;i<argc;i++)
   ConsolePrintf("argv[%u]=\"%s\"\n",i, argv[i]);

  return 0;                                       /* exit NLM */
}

3.2 hello.def - NLM header file

#
# hello.def - NLM Header definition file for nlmconv(1)
# Copyright (c) 2000 Martin Hinner <martin at hinner.info>
#

# define startup object files
INPUT   hello.o
INPUT   /usr/nwsdk/lib/prelude.o            # clib startup code

# all imported functions and import lists
IMPORT  at /usr/nwsdk/imports/clib.imp         # Functions in CLIB.NLM
IMPORT  at /usr/nwsdk/imports/threads.imp      # Functions in THREADS.NLM

# NLM header...
OUTPUT  hello.nlm                           # output file
TYPE 0                                      # Ordinary NLM
VERSION 1,0,0                               # Version 1.0
COPYRIGHT "Copyright (c) 2000 Martin Hinner <martin at hinner.info>" # (c) ...
DESCRIPTION "Simple 'Hello world' NLM module." # title of nlm
SCREENNAME "System Console"                 # Default screen name

MODULE CLIB,THREADS                         # req'd modules

3.3 Makefile

# makefile for "hello world" NLM

CC = gcc
CFLAGS = -Wall -O2 -g -I/usr/nwsdk/include/ -nostdinc -fno-builtin -fpack-struct

hello.nlm:      hello.o hello.def
        nlmconv --output-target=nlm32-i386 -T hello.def

hello.o:        hello.c
        $(CC) $(CFLAGS) -c hello.c

3.4 GCC problems

You must pass these arguments to the gcc:

• -fno-builtin: GCC's fast builtin functions sometimes cause server to abend, so we don't want to use them.
• -nostdinc: Only include files in /usr/nwsdk/include are valid for NLMs (don't forget to use also -I/usr/nwsdk/include).
• -fpack-struct: GCC's struct packing method is not valid for Novell NetWare, so we won't use it. Thanks to Gabor Keresztvalvi for this information.
• -fno-canary-all-functions: If you have Immunix StackGuard GCC, we don't want to use it. StackGuard doesn't work under NetWare.

3.5 Testing the Module

Copy hello.nlm to the SYS:\SYSTEM directory on your NetWare server. Then, on the system console, type "load hello.nlm". If everything went fine, you should see NLM version information, a copyright message and "Hello world".