X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ian/git?p=subdirmk.git;a=blobdiff_plain;f=subdirmk%2Fregen.mk.in;h=65d75c2ebfc32db72ccb6e7e432ba4ee6b71cfda;hp=f9d7240d412dd0cbb2583b5e8a2bdb08e49fe18b;hb=3feffa3257a111e37dafd9684092726845d34f42;hpb=ac5e06a07b23212991e152370900361adee14a58

diff --git a/subdirmk/regen.mk.in b/subdirmk/regen.mk.in
index f9d7240..65d75c2 100644
--- a/subdirmk/regen.mk.in
+++ b/subdirmk/regen.mk.in
@@ -1,3 +1,7 @@
+# subdirmk - rules for regenerating makefiles etc.
+#  Copyright 2019 Mark Wooding
+#  Copyright 2019 Ian Jackson
+# SPDX-License-Identifier: LGPL-2.0-or-later
 
 CONFIGURE	?= configure
 CONFIGURE_AC 	?= $(CONFIGURE).ac
@@ -12,16 +16,32 @@ $(top_srcdir)/$(CONFIGURE): $(addprefix $(top_srcdir)/,$(CONFIGURE_ACS))
 $(CONFIG_STATUS): $(top_srcdir)/$(CONFIGURE)
 	./$(CONFIG_STATUS) --recheck
 
-MAKEFILES += subdirmk/regen.mk
+MAKEFILE_TEMPLATES += $(top_srcdir)/Perdir.sd.mk
+MAKEFILE_TEMPLATES += $(addprefix $(top_srcdir)/, $(addsuffix .in, \
+	@_SUBDIRMK_MAKEFILES@ \
+	))
 
-main.mk $(MAKEFILES): makefiles.phantom ;
-.INTERMEDIATE: makefiles.phantom
-makefiles.phantom: 						\
+main.mk $(MAKEFILES): .makefiles.stamp ;
+.makefiles.stamp: 						\
 		$(top_srcdir)/subdirmk/generate			\
 		$(CONFIG_STATUS)				\
-		$(top_srcdir)/Perdir.mk.in			\
-		$(foreach m,$(MAKEFILES),$(top_srcdir)/$(m).in)
-	./$(CONFIG_STATUS)
+		$(MAKEFILE_TEMPLATES)
+# This filtering arranges that we can often run config.status to
+# generate only particular output files.  We look for *inputs* that
+# have changed.  If the only inputs that have changed are ones that we
+# know affect only one output (Subdir.mk.in and regen.mk.in), we pass
+# config.status the corresponding output file names.  Otherwise we
+# pass nothing and config.status does them all.  We need to mention
+# regen.mk.in twice because if $(top_srcdir) is `.', make elides the
+# directory part from $?.
+	./$(CONFIG_STATUS) $(if					\
+		$(filter-out Subdir.sd.mk %/Subdir.sd.mk	\
+			     %.mk.in				\
+			, $?),,					\
+		$(sort						\
+			$(patsubst %.sd.mk,%.mk,$(filter %.sd.mk,$?)) \
+			$(patsubst %.mk.in,%.mk,$(filter %.mk.in,$?))))
+	touch $@
 
 realclean:: clean
 	$(RM) config.status config.log