Line	Description
======= =======================================================================

?MAKE:	The ?MAKE: line records dependencies

    ?MAKE:symbol list: dependency list [+optional]

	This is the first dependency line. The first "symbol list"
	should list all the symbols built by this unit (i.e. whose
	value is computed by the shell section of the unit). Symbols
	should be space separated. If a defined symbol is for internal
	use only and should not appear in the generated "config.sh"
	file, then it should be preceded by a '+' (not to be confused
	with optional dependencies defined hereafter).
	The second part of the list (after the middle ':') is the unit
	dependency.  It should list all the needed special units, as
	well as all the symbols used by the shell implementation. If
	a symbol is needed but its configuration value is not critical,
	it can be preceded by a '+', in which case it is called a
	conditional dependency: its corresponding unit will be loaded
	if, and only if, that symbol is otherwise really wanted;
	otherwise the default value will be used.

    ?MAKE: <tab> command

	There can be one or more command lines following the initial
	dependency lines.  Those commands will be executed when the
	unit is wanted to load them into "Configure".
	Note that the leading <tab> character is required before the
	"command".

?INIT:	Initializations printed verbatim

?LINT:	Hints for metalint

	set		Listed variables are set
	    ?LINT:set d_getservprotos
	describe	Listed shell variables are described
	    ?LINT:describe awk ar bash bison byacc cat chgrp chmod chown
	create		Listed created files in regular units
	    ?LINT:create mips
	known		Listed C variables are described
	    ?LINT:known StGiFy
	change		Shell variable ok to be changed
	    ?LINT:change CONFIG_H
	extern		Variables known to be externally defined
	    ?LINT:extern CONFIG_H
	usefile		Files marked as being used
	    ?LINT:usefile foobar
	use		Variables declared as used by unit
	    ?LINT:use PERL_CONFIG_SH
	define		Listed variables are defined
	    ?LINT:define fieldn
	empty		Empty unit file
	    ?LINT:empty
	unclosed	Unclosed here-documents
	    ?LINT:unclosed EOT
	nothere		Not a here-document name
	nocomment	OK if leading unit ': comment' missing
	    ?LINT:nocomment

?RCS:	RCS comments are ignored

	To be used for RCS comments, at the top of the unit.

?C:	C symbols

	Comments for #defines

?D:	Default value for conditional symbols

	?D:osname=''

?E:	Example of usage

?F:	Produced files

	Defines what files are created by this module

	Files produced in the UU directory and which are identified by the
	convention ./filename. Files !filename are not produced, i.e. they are
	temporary or externally provided.

	?F:cppstdin !testcpp.out !testcpp.c

?H:	Process the config.h lines

	Defines the part to be included in the generated config_h.SH

	To get #ifdefs in config_h.SH, you'll need strange constructs like

	?H:?%<:@if USE_SITECUSTOMIZE
	?H:?%<:#ifndef USE_SITECUSTOMIZE
	?H:?%<:#$usesitecustomize     USE_SITECUSTOMIZE               /**/
	?H:?%<:#endif
	?H:?%<:@end

?I:	Added includes

?L:	Added libraries

?M:	Process the confmagic.h lines

?O:	Unit obsolescence

?P:	Location of PD implementation file

?S:	Shell variables

    ?S:symbol_name (obsolete symbol list)]:

	Introduces a shell symbol. This first line names the symbol,
	optionally followed by a list enclosed between parenthesis and
	giving the obsolete equivalent. Those obsolete symbols will be
	remapped to the new "symbol_name" if the -o option is given to
	"metaconfig".

    ?S: <tab> any text, for "Porting/Glossary"

	Basically a comment describing the shell symbol, which will be
	extracted by "makegloss" into the Glossary file.

    ?S:.

	Closes the shell symbol comment.

?T:	Shell temporaries used

	What variables are used as temporary variables

?V:	Visible symbols like 'rp', 'dflt'

	?V:fieldn

?W:	Wanted value for interpreter

?X:	User comment is ignored

	General purpose comments. May appear anywhere in the unit but must be
	left justfied. For RCS comments, please use the ?RCS: comment form.

?Y:	User-defined layout preference

	Declare a layout directive for this unit. That directive may be one
	of the strings "top", "default" or "bottom" (case does not matter,
	recommended style is to spell them out uppercased). If omitted,
	"default" is assumed.

	This directive is only required if you wish to force a unit at the
	top or the bottom of the generated "Configure" script, as unit
	dependencies permit it. Important questions may thus be forced
	at the beginning. Within the same layout class, units are sorted
	alphabetically with two special cases for d_* and i_* units, forced
	respectively at the top and bottom of their classes (but these
	should belong to the default class).

	It you force at the top a unit whose dependencies require all the
	other unit to precede it, you achieve nothing interesting. Therefore,
	that directive should really be used to increase the priority of
	some interactive units that do not depend on many other user-visible
	symbols, like path-related questions.

	?Y:TOP

lines can be made conditional (see Config_sh.U)

@if d_portable
:
:
@end
