Documented extended static rules.

make.texinfo

@@ -6,7 +6,10 @@
 $Header$
 
 $Log$
-Revision 1.17  1988/05/18 16:26:55  mcgrath
+Revision 1.22  1988/05/20 17:00:49  mcgrath
+Documented extended static rules.
+
+Revision 1.17  88/05/18  16:26:55  mcgrath
 Fixed a couple Texinfo bugs.
 
 Revision 1.16  88/05/15  18:58:00  mcgrath
@@ -181,6 +184,8 @@ be recompiled, or how.  @xref{Running}.
 
 * Implicit::	Implicit rules take over if the makefile doesn't say
 		 how a file is to be remade.
+* Static::	Extended static rules provide a compromise between explicit
+		 rules and implicit rule assumptions.
 * Archives::	How to use @code{make} to update archive files.
 * Missing::	Features of other @code{make}s not supported by GNU @code{make}.
 
@@ -3994,7 +3999,76 @@ The name of the first dependency that came via the implicit rule.
 For @code{.DEFAULT} commands, as for non-implicit commands, @samp{$*}
 and @samp{$<} are empty.  @samp{$@@} is @var{t}, as always.
 
-@node Archives, Missing, Implicit, Top
+@node Static, Archives, Implicit, Top
+@chapter Extended Static Rules
+@cindex extended static rules
+@cindex static rules
+@cindex explicit rules
+
+@dfn{Static rules}, or @dfn{explicit rules} are simple rules where you give
+the dependencies and commands for the targets.  @dfn{Implicit rules}
+(@pxref{Implicit}) are rules generated by @code{make} for which you specify
+only the target (and perhaps some implicit rules in addition to the
+standard set), and the dependencies and commands are figured out for you.
+@dfn{Extended static rules} provide a compromise between these two types of
+rules.  They have the flexibility of implicit rules, but do not depend on
+the contents of any directory to determine what is made from what.
+
+Extended static rules are basically implicit rules that are applied to a
+limited set of targets, rather than just any target that has no commands of
+its own.  The syntax of this type of rule follows directly from this
+explanation:
+
+@example
+@var{targets}: @var{target-pattern}: @var{dep} @dots{}; @var{command}
+	@var{command}
+	@dots{}
+@end example
+
+The first part of this rule, ``@var{targets}:'' gives the list of targets
+that the rule applies to.  These targets are filenames, possibly containing
+wildcard characters, just like the targets of ordinary explicit rules.
+The rest of the rule resembles an implicit pattern rule.  It has a target
+pattern containing a @samp{%} character and dependency filenames, each of
+which may contain a @samp{%} which is replaced by what matched the @samp{%}
+in the target pattern.
+
+In extended static rules, each target must match the target pattern; a
+warning is issued for each that does not.  If you have a list of files,
+only some of which will match the pattern, you can use the @samp{filter}
+function to remove nonmatching filenames:
+
+@example
+files := foo.elc bar.o
+
+$(filter %.o,$(files)): %.o: %.c; cc $< -o $@@
+$(filter %.elc,$(files)): %.elc: %.el; el-compile $< -o $@@
+@end example
+
+This type of rule is better than implicit rules in some situations
+for a few reasons:
+
+@itemize @bullet
+@item
+You may wish to have a different pattern rule apply to one set of files
+than applies to all others.
+
+@item
+If you cannot be sure of the contents of the directories in which your
+targets reside (or those listed in @code{vpath} search paths or the
+@code{VPATH} variable; @pxref{Directory Search}), you may want to
+circumvent possible unintended actions by @code{make} resulting from the
+wrong implicit rule matching.
+
+@item
+You may simply be of the opinion that implicit rules are inherently not
+particularly wonderful and would rather tell @code{make} exactly what to do
+with what, but without all the trouble of ordinary explicit rules.
+(This is included because that appears to be the opinion of the person who
+originally suggested the concept of extended static rules.)
+@end itemize
+
+@node Archives, Missing, Static, Top
 @chapter Using @code{make} to Update Archive Files
 @cindex archive