PORTING

--- INTRODUCTION

Just a quick note on porting and sending me patches:

First off, you probably should subscribe to
ucd-snmp-coders@ece.ucdavis.edu by sending a message to
ucd-snmp-coders-request@ece.ucdavis.edu with a subject line of
subscribe.  This is a mailing list to discuss all oft the coding
aspects of the project.

Quite a while back I started using the GNU autoconf testing suite to
greatly enhance portability.  Because of this porting to new
architectures is much easier than before.  However, new people porting
the package to new architectures rarely take advantage of this setup
and send me patches with lots of '#ifdef ARCH' type C code in it.  Let
me say up front, I *hate* this type of coding now (even though I used
to use it a lot).  What is better is to check for the necissary
functionality using the configure script and then use the results of
those tests.

To do this, you need to install the GNU 'autoconf' package which also
requires the GNU 'm4' (gm4) package as well.  This double installation
is extremely easy and shouldn't take you more than 15 minutes max.
After that, modify the configure.in and acconfig.h files as needed
instead of modifying the config.h or configure files directly.  The
Makefile will re-produce these files from the first two.

Worst case: Don't put in #ifdef architecture style statements.
Rather, create a new define in the s/ and m/ system specific header
files and use those defines to test against in the C code.  This
should only be done for things that can't be checked using configure
though.

Some autoconf examples:

--- HEADER FILES

In configure.in:
  AC_CHECK_HEADERS(headdir/header.h)

Then in your source code:
  #ifdef HAVE_HEADDIR_HEADER_H
    #include <headdir/header.h>
  #ENDIF

--- LIBRARY ROUTIENS

In configure.in:
  AC_CHECK_LIB(libexample, example_function)

Thats it.  The Makefiles will automatically link against -llibexample
if example_function is found in the library.

--- FUNCTION CHECKS

In configure.in:
  AC_CHECK_FUNCS(example_function)

In source code:
  #ifdef HAVE_EXAMPLE_FUNCTION
    /* use it */
  #endif

--- STRUCTURE MEMBER CHECKS

In configure.in:
  AC_CHECK_STRUCT_FOR([
#include lines
], STRUCTURE, MEMBER)
   ^^^^^^^^^  ^^^^^^  (change)

In acconfig.h:
  #undef STRUCT_STRUCTURE_HAS_MEMBER
                ^^^^^^^^^     ^^^^^^  (change)

In source code:
  #ifdef STRUCT_STRUCTURE_HAS_MEMBER
    /* use it */
  #endif

--- READ THE MANUAL

The GNU autoconf info files are extremely well written and easy to
follow.  Please check them out.

I'd be happy to help you through anything you don't understand or
through more complex examples (eg, checking for structure parts or
existance).  I'd be far less happy to get patches ignoring the above
request.  If you simple can't abide by this, please send the patches
anyway, but it'll just take me longer to get them applied.

Mail the patches to ucd-snmp-coders@ece.ucdavis.edu.  Please include
what version of the ucd-snmp package it was applied to and state the
arcitectures you have tested it on.

Thanks a lot for the consideration,
Wes