Re: [patches] First cut at simple option group support

[Jim Blandy <jimb@xxxxxxxxxxxxxxxx>]

Richard, here's a revision of the patch that implements (my
understanding of) your suggestion.  Does this look better?

I've made some other minor changes:

- I renamed the config file to 'option-groups.config'.  Naming some
  part of EGLIBC 'eglibc' is only meaningful when one is trying to
  draw a contrast with something else, as is the case with
  'ChangeLog.eglibc' opposing itself to GLIBC's 'ChangeLog'.
  Otherwise, it's a wasted opportunity to say something more
  meaningful.

- I renamed our toy catgets option group OPTION_EGLIBC_CATGETS.
  The groups suggested by POSIX will have names like
  OPTION_POSIX_NETWORKING and OPTION_XSI_I18N; since the catgets
  option is our own invention, it seems appropriate for the name to
  live in an 'EGLIBC' namespace.

- I expanded the comments in option-groups.def.


ChangeLog.eglibc:
2006-12-08  Jim Blandy  <jimb@xxxxxxxxxxxxxxxx>

	Add rudimentary option group support.
	* option-groups.mak, option-groups.def, option-groups.defaults:
       New files.
	* Makerules: Add contents of enabled option groups to the values
	of the variables 'routines', 'others', 'install-bin',
	'install-sbin', 'extra-objs', 'tests', and 'test-srcs'.
	* catgets/Makefile: Add the catgets directory's routines and
	programs to the OPTION_EGLIBC_CATGETS option group.

Index: option-groups.def
===================================================================
--- option-groups.def	(revision 0)
+++ option-groups.def	(revision 0)
@@ -0,0 +1,44 @@
+# This file documents the option groups EGLIBC currently supports, in
+# a format akin to the Linux Kconfig system's.  The syntax may change
+# over time.
+#
+# An entry of the form:
+#
+#   config OPTION_GROUP_NAME
+#       bool "one-line explanation of what this option group controls"
+#       help
+#           Multi-line help explaining the option group's meaning in
+#           some detail, terminated by indentation level.
+#
+# defines an option group whose variable is OPTION_GROUP_NAME, with
+# meaningful values 'y' (enabled) and 'n' (disabled).  The
+# documentation is formatted to be consumed by some sort of
+# interactive configuration interface, but EGLIBC doesn't have such an
+# interface yet.
+# 
+# Option group variables get their default values from the file
+# 'option-groups.defaults', in the top directory of the EGLIBC source
+# tree.  By default, all EGLIBC option groups are enabled --- their
+# variables are set to 'y'.
+#
+# After including 'option-groups.defaults', the EGLIBC make machinery
+# includes the file 'option-groups.config' from the top of the build
+# tree, if it is present.  Developers can place assignments to option
+# group variables in that file to override the defaults.  For example,
+# to disable an option group, place a line of the form:
+#
+#    OPTION_GROUP_NAME = n
+#
+# in 'option-groups.config' at the top of your build tree.  To
+# explicitly enable an option group, you may also write:
+#
+#    OPTION_GROUP_NAME = y
+# 
+# although this simply reestablishes the value already set by
+# 'option-groups.defaults'.
+
+config OPTION_EGLIBC_CATGETS
+   bool "Functions for accessing message catalogs"
+   help
+       This option group includes functions for accessing message
+       catalogs: catopen, catclose, and catgets.
Index: catgets/Makefile
===================================================================
--- catgets/Makefile	(revision 157175)
+++ catgets/Makefile	(working copy)
@@ -21,16 +21,18 @@
 #
 subdir	:= catgets
 
+include ../option-groups.mak
+
 headers		= nl_types.h
 distribute	= catgetsinfo.h config.h xopen-msg.sed test1.msg test2.msg \
 		  test-gencat.sh sample.SJIS
-routines	= catgets open_catalog
-others		= gencat
-install-bin	= gencat
-extra-objs	= $(gencat-modules:=.o)
+routines-$(OPTION_EGLIBC_CATGETS)    := catgets open_catalog
+others-$(OPTION_EGLIBC_CATGETS)      := gencat
+install-bin-$(OPTION_EGLIBC_CATGETS) := gencat
+extra-objs-$(OPTION_EGLIBC_CATGETS)  := $(gencat-modules:=.o)
 
-tests = tst-catgets
-test-srcs = test-gencat
+tests-$(OPTION_EGLIBC_CATGETS)       := tst-catgets
+test-srcs-$(OPTION_EGLIBC_CATGETS)   := test-gencat
 
 gencat-modules	= xmalloc
 
Index: option-groups.mak
===================================================================
--- option-groups.mak	(revision 0)
+++ option-groups.mak	(revision 0)
@@ -0,0 +1,17 @@
+# Setup file for subdirectory Makefiles that define EGLIBC option groups.
+
+# Read the default settings for all options.
+include $(..)option-groups.defaults
+
+# Read the developer's option group selections, overriding the
+# defaults from option-groups.defaults.
+-include $(objdir)/option-groups.config
+
+# Establish 'routines-y', etc. as simply expanded variables.
+routines-y     :=
+others-y       :=
+install-bin-y  :=
+install-sbin-y :=
+extra-objs-y   :=
+tests-y        :=
+test-srcs-y    :=
Index: Makerules
===================================================================
--- Makerules	(revision 157175)
+++ Makerules	(working copy)
@@ -405,6 +405,16 @@
 endef
 endif
 
+# Include targets in the selected option groups.
+routines     += $(routines-y)
+others       += $(others-y)
+install-bin  += $(install-bin-y)
+install-sbin += $(install-sbin-y)
+extra-objs   += $(extra-objs-y)
+tests        += $(tests-y)
+test-srcs    += $(test-srcs-y)
+
+
 # Modify the list of routines we build for different targets
 
 ifeq (yesyes,$(build-shared)$(elf))
Index: option-groups.defaults
===================================================================
--- option-groups.defaults	(revision 0)
+++ option-groups.defaults	(revision 0)
@@ -0,0 +1,11 @@
+# This file sets default values for all option group variables
+# mentioned in option-groups.def; see that file for a description of
+# each option group.
+#
+# Subdirectory makefiles include this file before including the user's
+# settings from option-groups.config at the top of the build tree;
+# that file need only refer to those options whose default settings
+# are to be changed.
+#
+# By default, all option groups are enabled.
+OPTION_EGLIBC_CATGETS = y