Configuring and Managing MPE/iX Internet Services (August 2002)

Chapter 9
HP WebWise MPE/iX Secure Web Server
Module Creation Using a Template
167
Module Creation Using a Template
Any existing Apache module can be used as a template for a new module. Mod_example.c is distributed with
Apache in /APACHE/PUB/libexec and makes a useful template for a simple module. When compiled and
linked as the shared library (NMXL) mod_example.so, this module is a fully working DSO. The module
libexec/mod_example.so has already been pre-built.
For a more functional module, try a different module as your template. For instance, to create a new module
that does authentication, starting with one of Apache’s authentication modules may be more appropriate. If
you want to create a module that has its own configuration directives, start with another module that already
does this.
To create the module file “mod_hw.c” from file “mod_example.c”, log on as MGR.APACHE so that the file is
created with the right ownership:
:HELLO MGR.APACHE
:XEQ SH.HPBIN.SYS -L
shell/iX> mkdir hw
shell/iX> cd hw
shell/iX> cp /APACHE/PUB/libexec/mod_example.c mod_hw.c
Change all references inside mod_hw.c from mod_example, example_module, example_handler, etc. to
mod_hw, hw_module, hw_handler, etc., and modify/add any other code, as needed. Creating a separate
directory for the module, such as hw, separates it from other modules under development.
To compile a module, certain compile options must be specified and the Apache C header files must also be
included. Below, gcc creates two object files, hw.o and mod_hw.o, using the necessary options and include
files. Use the -c option for compilation:
shell/iX> gcc -DMPE -D_POSIX_SOURCE -D_SOCKET_SOURCE
-DNO_DBM_REWRITEMAP -DUSE_HSREGEX -DEAPI -DSHARED_MODULE
-I/APACHE/PUB/include -c mod_hw.c hw.c
Next, link the module. The link steps will be different when calling external functions that reside in archive
or shared libraries. Other examples of linking are shown later.
To link, the MPE/iX LinkEditor can be called from the CI or the POSIX shell:
:linkedit
or
shell/iX> callci linkedit
LinkEd> buildxl xl=./mod_hw.so;limit=5
LinkEd> addxl from=./mod_hw.o,./hw.o;to=./mod_hw.so;
rl=/lib/libm.a,/lib/libc.a;merge;share
1 OBJECT FILE HAS BEEN ADDED.
The “rl=” option is used to specify which archive libraries are used to resolve external function calls. The
math library (/lib/libm.a) is specified here to resolve pow() in mod_hw.o. /lib/libc.a is not actually
needed by the sample code. But it is a good practice to always specify libc since most modules and other
libraries are likely to need functions from this library. If libc is not specified explicitly as shown here, the
MPE/iX C library will be used by default (LIBC.LIB.SYS). Since Apache is built with libc, we recommend
explicitly specifying /lib/libc instead of defaulting to LIBC.LIB.SYS. /lib/libc and LIBC.LIB.SYS are not
identical. The order of the libraries listed by “rl=” is important and libc should always be specified last. The