This is a loose collection of notes for people hacking on simulators.
If this document gets big enough it can be prettied it up then.

Contents

- The "common" directory
- Common Makefile Support
- Generating "configure" files

The "common" directory
======================

The common directory contains:

- common documentation files (e.g. run.1, and maybe in time .texi files)
- common source files (e.g. run.c)
- common Makefile fragment and configury (e.g. Make-common.in, aclocal.m4).

In addition "common" contains portions of the system call support
(e.g. callback.c, nltvals.def).

Even though no files are built in this directory, it is still configured
so support for regenerating nltvals.def is present.

Common Makefile Support
=======================

A common configuration framework is available for simulators that want
to use it.  The common framework exists to remove a lot of duplication
in configure.in and Makefile.in, and it also provides a foundation for
enhancing the simulators uniformly (e.g. the more they share in common
the easier a feature added to one is added to all).

The configure.in of a simulator using the common framework should look like:

--- snip ---
dnl Process this file with autoconf to produce a configure script.
sinclude(../common/aclocal.m4)
AC_PREREQ(2.5)dnl
AC_INIT(Makefile.in)

SIM_AC_COMMON

... target specific additions ...

SIM_AC_OUTPUT
--- snip ---

SIM_AC_COMMON:

- invokes the autoconf macros most often used by the simulators
- defines --enable/--with options usable by all simulators
- initializes sim_link_files/sim_link_links as the set of symbolic links
  to set up

SIM_AC_OUTPUT:

- creates the symbolic links defined in sim_link_{files,links}
- creates config.h
- creates the Makefile

The Makefile.in of a simulator using the common framework should look like:

--- snip ---
# Makefile for blah ...
# Copyright blah ...

## COMMON_PRE_CONFIG_FRAG

# These variables are given default values in COMMON_PRE_CONFIG_FRAG.
# We override the ones we need to here.
# Not all of these need to be mentioned, only the necessary ones.

# List of object files, less common parts.
SIM_OBJS =
# List of flags to always pass to $(CC).
SIM_EXTRA_CFLAGS =
# List of extra libraries to link with.
SIM_EXTRA_LIBS =
# List of extra program dependencies.
SIM_EXTRA_LIBDEPS =
# List of main object files for `run'.
SIM_RUN_OBJS = run.o
# Dependency of `all' to build any extra files.
SIM_EXTRA_ALL =
# Dependency of `install' to install any extra files.
SIM_EXTRA_INSTALL =
# Dependency of `clean' to clean any extra files.
SIM_EXTRA_CLEAN =

## COMMON_POST_CONFIG_FRAG

# Rules need to build $(SIM_OBJS), plus whatever else the target wants.

... target specific rules ...
--- snip ---

COMMON_{PRE,POST}_CONFIG_FRAG are markers for SIM_AC_OUTPUT to tell it
where to insert the two pieces of common/Make-common.in.
The resulting Makefile is created by doing autoconf substitions on
both the target's Makefile.in and Make-common.in, and inserting
the two pieces of Make-common.in into the target's Makefile.in at
COMMON_{PRE,POST}_CONFIG_FRAG.

Generating "configure" files
============================

For target's using the common framework, "configure" can be generated
by running autoconf.  This works because configure.in contains
"sinclude(../common/aclocal.m4)".

To regenerate the configure files for all targets using the common framework:

	$  cd devo/sim
	$  make -f Makefile.in autoconf-common

To add a change-log entry to the ChangeLog file for each updated
directory (WARNING - check the modified new-ChangeLog files before
renaming):

	$  make -f Makefile.in autoconf-changelog
	$  more */new-ChangeLog
	$  make -f Makefile.in autoconf-install

In a similar vein, both the configure and config.in files can be
updated using the sequence:

	$  cd devo/sim
	$  make -f Makefile.in autoheader-common
	$  make -f Makefile.in autoheader-changelog
	$  more */new-ChangeLog
	$  make -f Makefile.in autoheader-install