libstdc++: Simplify build targets for debug library

This rewrites the stamp-debug and build-debug targets in src/Makefile so
that each generated Makefile in the debug/$(SUBDIRS) directories is a
make target, instead of being created by a loop in the stamp-debug
recipe. The final adjustments to debug/Makefile are done as part of the
stamp-debug target instead of the build-debug target.

The advantage is that each $(SUBDIRS)/debug/Makefile now has the
corresponding $(SUBDIRS)/Makefile as a prerequisite, so they will be
regenerated if needed. Generating those can also be parallelized by
make, although those steps are very fast so that doesn't really matter.

This also removes the duplication in the stamp-debug recipe, which was
using exactly the same sed command for debug/Makefile and each
debug/$(SUBDIRS)/Makefile. That is done by adding "." to the list of
subdirectories to process. The recipes can also be simplified to use
separate shell commands per line, instead of using backslashes to join
the whole recipe into a single shell command.

Also replace 'echo `date` > stamp-xxx' with just 'date > stamp-xxx'
which is equivalent but simpler.

libstdc++-v3/ChangeLog:

	* src/Makefile.am: Simplify debug build targets.
	* src/Makefile.in: Regenerate.

2 files changed, 56 insertions, 79 deletions

diff --git a/libstdc++-v3/src/Makefile.am b/libstdc++-v3/src/Makefile.am
index b83c222..b545ebf 100644
--- a/libstdc++-v3/src/Makefile.am
+++ b/libstdc++-v3/src/Makefile.am
@@ -30,10 +30,8 @@ endif
 
 if ENABLE_BACKTRACE
 backtrace_dir = libbacktrace
-backtrace_supported_h = $(backtrace_dir)/backtrace-supported.h
 else
 backtrace_dir =
-backtrace_supported_h =
 endif
 
 ## Keep this list sync'd with acinclude.m4:GLIBCXX_CONFIGURE.
@@ -370,7 +368,7 @@ libstdc++convenience.la: $(toolexeclib_LTLIBRARIES)
 	if test ! -f .libs/libstdc++.a; then \
 	  cp .libs/libstdc++convenience.a .libs/libstdc++.a; \
 	fi; \
-	echo `date` > stamp-libstdc++convenience;
+	date > stamp-libstdc++convenience;
 
 # Added rules.
 # 1 debug library
@@ -386,50 +384,41 @@ CLEAN_DEBUG =
 endif
 
 # Build a debug variant.
+
 # Take care to fix all possibly-relative paths.
-debugdir = ${glibcxx_builddir}/src/debug
-stamp-debug: Makefile $(foreach dir,$(SUBDIRS),$(dir)/Makefile)
-	if test ! -d ${debugdir} || test ! -f ${debugdir}/Makefile ; then \
-	  mkdir -p ${debugdir}; \
-	  for d in $(SUBDIRS); do mkdir -p  ${debugdir}/$$d; done; \
-	  (cd ${debugdir}; \
-	  sed -e 's/top_builddir = \.\./top_builddir = ..\/../' \
-	      -e 's/top_build_prefix = \.\./top_build_prefix = ..\/../' \
-	      -e 's/srcdir = \.\./srcdir = ..\/../' \
-	      -e 's/VPATH = \.\./VPATH = ..\/../' \
-	      -e 's/glibcxx_basedir = \.\./glibcxx_basedir = ..\/../' \
-	      -e 's/MKDIR_P = \.\./MKDIR_P = ..\/../' \
-	  < ../Makefile > Makefile ; \
-	  for d in . $(SUBDIRS); do \
-	  sed -e 's/top_builddir = \.\./top_builddir = ..\/../' \
-	      -e 's/top_build_prefix = \.\./top_build_prefix = ..\/../' \
-	      -e 's/srcdir = \.\./srcdir = ..\/../' \
-	      -e 's/VPATH = \.\./VPATH = ..\/../' \
-	      -e 's/glibcxx_basedir = \.\./glibcxx_basedir = ..\/../' \
-	      -e 's/MKDIR_P = \.\./MKDIR_P = ..\/../' \
-	  < ../$$d/Makefile > $$d/Makefile ; \
-	  done) ; \
-	fi; \
-	echo `date` > stamp-debug;
+debug/%/Makefile: %/Makefile
+	$(MKDIR_P) $(dir $@)
+	sed -e 's/top_builddir = \.\./top_builddir = ..\/../' \
+	    -e 's/top_build_prefix = \.\./top_build_prefix = ..\/../' \
+	    -e 's/srcdir = \.\./srcdir = ..\/../' \
+	    -e 's/VPATH = \.\./VPATH = ..\/../' \
+	    -e 's/glibcxx_basedir = \.\./glibcxx_basedir = ..\/../' \
+	    -e 's/MKDIR_P = \.\./MKDIR_P = ..\/../' \
+	  < $< > $@
+
+stamp-debug: $(foreach dir,. $(SUBDIRS),debug/$(dir)/Makefile)
+	mv debug/Makefile debug/Makefile.tmp
+	sed -e 's,all-local: all-once,all-local:,' \
+	    -e 's,install-data-local: install-data-once,install-data-local:,' \
+	    -e '/vpath/!s,src/c,src/debug/c,' \
+	  < debug/Makefile.tmp > debug/Makefile
+	rm -f debug/Makefile.tmp
+	date > stamp-debug;
+
+.SECONDARY: $(foreach dir,. $(SUBDIRS),debug/$(dir)/Makefile)
 
 if ENABLE_BACKTRACE
-${debugdir}/$(backtrace_supported_h): $(backtrace_supported_h) stamp-debug
+backtrace_supported_h = $(backtrace_dir)/backtrace-supported.h
+debug_backtrace_supported_h = debug/$(backtrace_supported_h)
+$(debug_backtrace_supported_h): $(backtrace_supported_h) stamp-debug
 	cp $< $@
-debug_backtrace_supported_h = ${debugdir}/$(backtrace_supported_h)
 else
 debug_backtrace_supported_h =
 endif
 
 build-debug: stamp-debug $(debug_backtrace_supported_h)
-	  (cd ${debugdir}; \
-	  mv Makefile Makefile.tmp; \
-	  sed -e 's,all-local: all-once,all-local:,' \
-	      -e 's,install-data-local: install-data-once,install-data-local:,' \
-	      -e '/vpath/!s,src/c,src/debug/c,' \
-	  < Makefile.tmp > Makefile ; \
-	  rm -f Makefile.tmp ; \
-	  $(MAKE) CXXFLAGS='$(DEBUG_FLAGS)' \
-	  toolexeclibdir=$(glibcxx_toolexeclibdir)/debug all) ;
+	  $(MAKE) -C debug CXXFLAGS='$(DEBUG_FLAGS)' \
+	    toolexeclibdir=$(glibcxx_toolexeclibdir)/debug all
 
 # Install debug library.
 install-debug: build-debug
diff --git a/libstdc++-v3/src/Makefile.in b/libstdc++-v3/src/Makefile.in
index 41a00f7..f54ee28 100644
--- a/libstdc++-v3/src/Makefile.in
+++ b/libstdc++-v3/src/Makefile.in
@@ -485,8 +485,6 @@ AM_CPPFLAGS = $(GLIBCXX_INCLUDES) $(CPPFLAGS)
 @ENABLE_FILESYSTEM_TS_TRUE@filesystem_dir = filesystem
 @ENABLE_BACKTRACE_FALSE@backtrace_dir = 
 @ENABLE_BACKTRACE_TRUE@backtrace_dir = libbacktrace
-@ENABLE_BACKTRACE_FALSE@backtrace_supported_h = 
-@ENABLE_BACKTRACE_TRUE@backtrace_supported_h = $(backtrace_dir)/backtrace-supported.h
 SUBDIRS = c++98 c++11 c++17 c++20 $(filesystem_dir) $(backtrace_dir)
 @VTV_CYGMIN_FALSE@toolexeclib_LTLIBRARIES = libstdc++.la
 
@@ -675,12 +673,9 @@ CXXLINK = \
 @GLIBCXX_BUILD_DEBUG_TRUE@STAMP_INSTALL_DEBUG = install-debug
 @GLIBCXX_BUILD_DEBUG_FALSE@CLEAN_DEBUG = 
 @GLIBCXX_BUILD_DEBUG_TRUE@CLEAN_DEBUG = debug
-
-# Build a debug variant.
-# Take care to fix all possibly-relative paths.
-debugdir = ${glibcxx_builddir}/src/debug
+@ENABLE_BACKTRACE_TRUE@backtrace_supported_h = $(backtrace_dir)/backtrace-supported.h
 @ENABLE_BACKTRACE_FALSE@debug_backtrace_supported_h = 
-@ENABLE_BACKTRACE_TRUE@debug_backtrace_supported_h = ${debugdir}/$(backtrace_supported_h)
+@ENABLE_BACKTRACE_TRUE@debug_backtrace_supported_h = debug/$(backtrace_supported_h)
 all: all-recursive
 
 .SUFFIXES:
@@ -1113,44 +1108,37 @@ libstdc++convenience.la: $(toolexeclib_LTLIBRARIES)
 	if test ! -f .libs/libstdc++.a; then \
 	  cp .libs/libstdc++convenience.a .libs/libstdc++.a; \
 	fi; \
-	echo `date` > stamp-libstdc++convenience;
-stamp-debug: Makefile $(foreach dir,$(SUBDIRS),$(dir)/Makefile)
-	if test ! -d ${debugdir} || test ! -f ${debugdir}/Makefile ; then \
-	  mkdir -p ${debugdir}; \
-	  for d in $(SUBDIRS); do mkdir -p  ${debugdir}/$$d; done; \
-	  (cd ${debugdir}; \
-	  sed -e 's/top_builddir = \.\./top_builddir = ..\/../' \
-	      -e 's/top_build_prefix = \.\./top_build_prefix = ..\/../' \
-	      -e 's/srcdir = \.\./srcdir = ..\/../' \
-	      -e 's/VPATH = \.\./VPATH = ..\/../' \
-	      -e 's/glibcxx_basedir = \.\./glibcxx_basedir = ..\/../' \
-	      -e 's/MKDIR_P = \.\./MKDIR_P = ..\/../' \
-	  < ../Makefile > Makefile ; \
-	  for d in . $(SUBDIRS); do \
-	  sed -e 's/top_builddir = \.\./top_builddir = ..\/../' \
-	      -e 's/top_build_prefix = \.\./top_build_prefix = ..\/../' \
-	      -e 's/srcdir = \.\./srcdir = ..\/../' \
-	      -e 's/VPATH = \.\./VPATH = ..\/../' \
-	      -e 's/glibcxx_basedir = \.\./glibcxx_basedir = ..\/../' \
-	      -e 's/MKDIR_P = \.\./MKDIR_P = ..\/../' \
-	  < ../$$d/Makefile > $$d/Makefile ; \
-	  done) ; \
-	fi; \
-	echo `date` > stamp-debug;
+	date > stamp-libstdc++convenience;
+
+# Build a debug variant.
 
-@ENABLE_BACKTRACE_TRUE@${debugdir}/$(backtrace_supported_h): $(backtrace_supported_h) stamp-debug
+# Take care to fix all possibly-relative paths.
+debug/%/Makefile: %/Makefile
+	$(MKDIR_P) $(dir $@)
+	sed -e 's/top_builddir = \.\./top_builddir = ..\/../' \
+	    -e 's/top_build_prefix = \.\./top_build_prefix = ..\/../' \
+	    -e 's/srcdir = \.\./srcdir = ..\/../' \
+	    -e 's/VPATH = \.\./VPATH = ..\/../' \
+	    -e 's/glibcxx_basedir = \.\./glibcxx_basedir = ..\/../' \
+	    -e 's/MKDIR_P = \.\./MKDIR_P = ..\/../' \
+	  < $< > $@
+
+stamp-debug: $(foreach dir,. $(SUBDIRS),debug/$(dir)/Makefile)
+	mv debug/Makefile debug/Makefile.tmp
+	sed -e 's,all-local: all-once,all-local:,' \
+	    -e 's,install-data-local: install-data-once,install-data-local:,' \
+	    -e '/vpath/!s,src/c,src/debug/c,' \
+	  < debug/Makefile.tmp > debug/Makefile
+	rm -f debug/Makefile.tmp
+	date > stamp-debug;
+
+.SECONDARY: $(foreach dir,. $(SUBDIRS),debug/$(dir)/Makefile)
+@ENABLE_BACKTRACE_TRUE@$(debug_backtrace_supported_h): $(backtrace_supported_h) stamp-debug
 @ENABLE_BACKTRACE_TRUE@	cp $< $@
 
 build-debug: stamp-debug $(debug_backtrace_supported_h)
-	  (cd ${debugdir}; \
-	  mv Makefile Makefile.tmp; \
-	  sed -e 's,all-local: all-once,all-local:,' \
-	      -e 's,install-data-local: install-data-once,install-data-local:,' \
-	      -e '/vpath/!s,src/c,src/debug/c,' \
-	  < Makefile.tmp > Makefile ; \
-	  rm -f Makefile.tmp ; \
-	  $(MAKE) CXXFLAGS='$(DEBUG_FLAGS)' \
-	  toolexeclibdir=$(glibcxx_toolexeclibdir)/debug all) ;
+	  $(MAKE) -C debug CXXFLAGS='$(DEBUG_FLAGS)' \
+	    toolexeclibdir=$(glibcxx_toolexeclibdir)/debug all
 
 # Install debug library.
 install-debug: build-debug