X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ian/git?p=subdirmk.git;a=blobdiff_plain;f=subdirmk%2Fregen.mk.in;h=b8e031f7686c929cf5e1da072162a43bebe621e3;hp=f9d7240d412dd0cbb2583b5e8a2bdb08e49fe18b;hb=b1f14d76cfc604fedd57499c6d8ce44a91391067;hpb=ac5e06a07b23212991e152370900361adee14a58

diff --git a/subdirmk/regen.mk.in b/subdirmk/regen.mk.in
index f9d7240..b8e031f 100644
--- a/subdirmk/regen.mk.in
+++ b/subdirmk/regen.mk.in
@@ -14,14 +14,29 @@ $(CONFIG_STATUS): $(top_srcdir)/$(CONFIGURE)
 
 MAKEFILES += subdirmk/regen.mk
 
-main.mk $(MAKEFILES): makefiles.phantom ;
-.INTERMEDIATE: makefiles.phantom
-makefiles.phantom: 						\
+MAKEFILE_TEMPLATES += $(top_srcdir)/Perdir.mk.in
+
+main.mk $(MAKEFILES): .makefiles.stamp ;
+.makefiles.stamp: 						\
 		$(top_srcdir)/subdirmk/generate			\
 		$(CONFIG_STATUS)				\
-		$(top_srcdir)/Perdir.mk.in			\
+		$(MAKEFILE_TEMPLATES)				\
 		$(foreach m,$(MAKEFILES),$(top_srcdir)/$(m).in)
-	./$(CONFIG_STATUS)
+# 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.mk.in %/Subdir.mk.in	\
+			subdirmk/regen.mk.in			\
+			$(top_srcdir)/subdirmk/regen.mk.in	\
+			, $?),,					\
+		$(sort $(patsubst %.mk.in,%.mk,$(filter %.mk.in,$?))))
+	touch $@
 
 realclean:: clean
 	$(RM) config.status config.log