Complete quiet and fast make -j N all support avoiding rebuilds of nut_version.h and libupsclient-version.h within the single run

Makefile.am

@@ -12,6 +12,10 @@
 # include directory for aclocal
 ACLOCAL_AMFLAGS = -I m4
 
+CLEANFILES =
+DISTCLEANFILES =
+MAINTAINERCLEANFILES =
+
 # Autotools' SUBDIRS (our values are listed below) allow for powerful recursive
 # recipe automation, with one notable weakness: the dirs are processed in a
 # loop sequentially, even in parallel builds (each such sub-make is parallel
@@ -91,13 +95,24 @@ SUBDIRS_ALL_LIBS_LOCAL = \
 #all all-recursive all-am-local all-local: all-fanout-maybe
 all-recursive: all-fanout-maybe
 
+all: all-fanout-cleanup
+
+# Run as part of "all", but after the autotools-standard "all-recursive"
+# where we quiesce nut_version.h regeneration attempts for each subdir
+all-fanout-cleanup: all-recursive
+	@rm -f include/.all.nut_version-generated.timestamp \
+	       clients/.all.libupsclient_version-generated.timestamp
+
 # Verbosity for fanout rule tracing; 0/1 (or "default" that may auto-set
 # to 0 or 1 in some rules below)
 SUBDIR_MAKE_VERBOSE = default
 
 # Run the standard build if going sequential (or with unknown MAKEFLAGS),
 # or fanout if parallel (presuming GNU/BSD/Sun make at least):
+CLEANFILES += include/.all.nut_version-generated.timestamp clients/.all.libupsclient_version-generated.timestamp
 all-fanout-maybe: @dotMAKE@
+	@rm -f include/.all.nut_version-generated.timestamp \
+	       clients/.all.libupsclient_version-generated.timestamp
 	+@if [ x"$(NUT_MAKE_SKIP_FANOUT)" = xtrue ] ; then \
 		if [ x"$(SUBDIR_MAKE_VERBOSE)" != x0 ] ; then \
 			echo "  SUBDIR-MAKE	$@: skip optimization for parallel make - NUT_MAKE_SKIP_FANOUT is set" ; \
@@ -216,6 +231,10 @@ SUBDIR_TGT_RULE = ( \
 all-libs-local/include: @dotMAKE@
 	+@NUT_VERSION_H_GENERATED=false; export NUT_VERSION_H_GENERATED; \
 	  $(SUBDIR_TGT_RULE)
+	@[ -s include/nut_version.h ]
+	@touch -r include/nut_version.h -d '-10 seconds' include/.all.nut_version-generated.timestamp && exit ; \
+	 touch -d '1970-01-01' include/.all.nut_version-generated.timestamp && exit ; \
+	 touch include/.all.nut_version-generated.timestamp
 
 ### Delivers: libcommon.la libcommonclient.la libcommonstr.la libcommonstrjson.la
 ###           (consume only one of these at a time!)
@@ -239,6 +258,10 @@ all-libs-local/common: all-libs-local/include @dotMAKE@
 all-libs-local/clients: all-libs-local/common @dotMAKE@
 	+@NUT_VERSION_H_GENERATED=true; export NUT_VERSION_H_GENERATED; \
 	  $(SUBDIR_TGT_RULE)
+	@[ -s clients/libupsclient-version.h ]
+	@touch -r clients/libupsclient-version.h -d '-10 seconds' clients/.all.libupsclient_version-generated.timestamp && exit ; \
+	 touch -d '1970-01-01' clients/.all.libupsclient_version-generated.timestamp && exit ; \
+	 touch clients/.all.libupsclient_version-generated.timestamp
 
 ### Delivers: libdummy_main.la libdummy_serial.la libdummy_upsdrvquery.la
 ### Delivers: libdummy_mockdrv.la libserial-nutscan.la
@@ -630,8 +653,8 @@ distcleancheck:
 realclean: maintainer-clean
 
 # Files made by our targets:
-CLEANFILES = *-spellchecked *.adoc-parsed cppcheck*.xml config.log.inplace-outer
-DISTCLEANFILES = ChangeLog
+CLEANFILES += *-spellchecked *.adoc-parsed cppcheck*.xml config.log.inplace-outer
+DISTCLEANFILES += ChangeLog
 
 # Most of the files generated by custom rules in the configure script
 # or by autogen.sh are cleaned by the Makefile.am in their directories.
@@ -647,7 +670,7 @@ DISTCLEANFILES += include/config.h.in~
 # from their installation, or made by `automake` etc. on the system
 # which generates `configure`; rebuilding NUT after deleting these
 # requires `autogen.sh` script to be re-run (and tools available):
-MAINTAINERCLEANFILES = INSTALL
+MAINTAINERCLEANFILES += INSTALL
 MAINTAINERCLEANFILES += aclocal.m4 config.guess config.sub
 MAINTAINERCLEANFILES += configure
 MAINTAINERCLEANFILES += depcomp install-sh ltmain.sh test-driver ar-lib
@@ -1048,10 +1071,13 @@ ChangeLog.adoc: ChangeLog @dotMAKE@
 	+cd $(abs_top_builddir)/docs && $(MAKE) $(AM_MAKEFLAGS) ../ChangeLog.adoc
 
 nut_version.h include/nut_version.h: @dotMAKE@
+	@rm -f include/.all.nut_version-generated.timestamp
 	+cd $(abs_top_builddir)/include && $(MAKE) $(AM_MAKEFLAGS) nut_version.h
 
+# May depend on nut_version.h at least when we ENABLE_SHARED_PRIVATE_LIBS
 # May involve (re-)build of libupsclient.la
-libupsclient-version.h clients/libupsclient-version.h: @dotMAKE@
+libupsclient-version.h clients/libupsclient-version.h: include/nut_version.h @dotMAKE@
+	@rm -f clients/.all.libupsclient_version-generated.timestamp
 	+cd $(abs_top_builddir)/include && $(MAKE) $(AM_MAKEFLAGS) libupsclient-version.h
 
 tools/gitlog2changelog.py: tools/gitlog2changelog.py.in @dotMAKE@

clients/.gitignore

@@ -1,3 +1,4 @@
+/.all.libupsclient_version-generated.timestamp
 /libupsclient-version.h
 /libupsclient-version.h.tmp*
 /upsimage.cgi

clients/Makefile.am

@@ -201,9 +201,27 @@ endif HAVE_WINDOWS
 #   dlname='libupsclient-6.dll'
 #   library_names='libupsclient.dll.a'
 #   libdir='//lib'
+# Note that volatile dependencies like nut_version.h can cause re-evaluation
+# of the libupsclient.la goal even if ultimately nothing has changed, and so
+# cause needless evaluations of libupsclient-version.h. We try a couple of
+# ways to skip this rebuild noise for common NUT parallel `make -j N all` runs.
 CLEANFILES += libupsclient-version.h libupsclient-version.h.tmp*
 libupsclient-version.h: libupsclient.la
-	@echo "  GENERATE-HEADER	$@" ; \
+	@if [ -s '$@' -a -s '$?' ] ; then \
+	    if test -n "`find '$@' -newer '$?' 2>/dev/null`" ; then \
+	        if [ x"$(MAINTAINER_GENERATE_HEADER_DEBUG)" = xyes ] ; then \
+	            echo "=== SKIP (include) $@ (libupsclient.la is older than the generated file - not remade when re-evaluated)" >&2; \
+	        fi ; \
+	        exit 0; \
+	    fi ; \
+	    if test -n "`find '$@' -newer '.all.libupsclient_version-generated.timestamp' 2>/dev/null`" ; then \
+	        if [ x"$(MAINTAINER_GENERATE_HEADER_DEBUG)" = xyes ] ; then \
+	            echo "=== SKIP (include) $@ (.all.libupsclient_version-generated.timestamp was made in this larger run and is older than the generated file)" >&2; \
+	        fi ; \
+	        exit 0 ; \
+	    fi ; \
+	 fi ; \
+	 echo "  GENERATE-HEADER	$@" ; \
 	 RES=0; \
 	 dlname_filter() { sed -e 's/^[^=]*=//' -e 's/^"\(.*\)"$$/\1/' -e 's/^'"'"'\(.*\)'"'"'$$/\1/' ; }; \
 	 SOFILE_LIBUPSCLIENT="`$(EGREP) '^dlname' '$?' | dlname_filter`" \

include/.gitignore

@@ -1,5 +1,6 @@
 /config.h
 /config.h.in
+/.all.nut_version-generated.timestamp
 /nut_version.h
 /nut_version.h.tmp*
 /stamp-h1

include/Makefile.am

@@ -45,12 +45,20 @@ MAINTAINERCLEANFILES = Makefile.in .dirstamp
 # (e.g. a commit tagged as 2.8.3-rc5 can have its own NUT_VERSION based
 # on 2.8.2-something, but is assumed as a pre-release for 2.8.3 SEMVER)
 nut_version.h: @FORCE_NUT_VERSION@
-	@if [ -s '$@' ] && ( [ x"$(NUT_VERSION_H_GENERATED)" = xtrue ] || [ x"$${NUT_VERSION_H_GENERATED}" = xtrue ] ) ; then \
-	    if [ x"$(MAINTAINER_GENERATE_HEADER_DEBUG)" = xyes ] ; then \
-	        echo "=== SKIP (include) $@ (NUT_VERSION_H_GENERATED makevar=$(NUT_VERSION_H_GENERATED) shellvar=$${NUT_VERSION_H_GENERATED})" >&2; \
+	@if [ -s '$@' ] ; then \
+	    if [ x"$(NUT_VERSION_H_GENERATED)" = xtrue ] || [ x"$${NUT_VERSION_H_GENERATED}" = xtrue ] ; then \
+	        if [ x"$(MAINTAINER_GENERATE_HEADER_DEBUG)" = xyes ] ; then \
+	            echo "=== SKIP (include) $@ (NUT_VERSION_H_GENERATED makevar=$(NUT_VERSION_H_GENERATED) shellvar=$${NUT_VERSION_H_GENERATED})" >&2; \
+	        fi ; \
+	        exit 0 ; \
 	    fi ; \
-	    exit 0 ; \
-	 fi ; \
+	    if test -n "`find '$@' -newer '.all.nut_version-generated.timestamp' 2>/dev/null`" ; then \
+	        if [ x"$(MAINTAINER_GENERATE_HEADER_DEBUG)" = xyes ] ; then \
+	            echo "=== SKIP (include) $@ (.all.nut_version-generated.timestamp was made in this larger run and is older than the generated file)" >&2; \
+	        fi ; \
+	        exit 0 ; \
+	    fi ; \
+	 fi; \
 	 if [ x"$(MAINTAINER_GENERATE_HEADER_DEBUG)" = xyes ] ; then \
 	    echo "  GENERATE-HEADER	$@ (NUT_VERSION_H_GENERATED makevar=$(NUT_VERSION_H_GENERATED) shellvar=$${NUT_VERSION_H_GENERATED})"; \
 	 else \