diff --git a/Mmakefile b/Mmakefile
index a66838b82..0dcfa8bfd 100644
--- a/Mmakefile
+++ b/Mmakefile
@@ -53,7 +53,7 @@ SUBDIRS = \
 
 MMAKEFLAGS =
 
-# We include ../../mfilterjavac in this path because $SUBDIR_MMAKE is used
+# We include ../../mfilterjavac in this path because $(SUBDIR_MMAKE) is used
 # from the grade install directories, and we need mfilterjavac in our path
 # when executing in install_grade_dir.java/library and others.
 SUBDIR_MMAKE = \
@@ -612,7 +612,7 @@ tar2: 	$(GENERATED_DOCS)
 	chmod -R a+r *
 	# Our invoker should have passed to us in ${SRCDIST_NAME}
 	# the name of the current directory in its parent directory.
-	# This name should have the form mercury-srcdist-$VERSION,
+	# This name should have the form mercury-srcdist-$(VERSION),
 	# which matters, because it will also be the name of the directory
 	# that the tar file we are creating here will unpack into.
 	#
@@ -929,7 +929,7 @@ bindist: WORK_IN_PROGRESS TODO
 
 #-----------------------------------------------------------------------------#
 
-clean: clean_tests clean_subdirs
+clean: clean_tests clean_subdirs clean_extras
 
 .PHONY: clean_subdirs
 clean_subdirs:
@@ -941,14 +941,20 @@ clean_subdirs:
 .PHONY: clean_tests
 clean_tests:
 	+if test -d tests; then \
-		(cd tests; $(SUBDIR_MMAKE) clean) \
+		(cd tests; $(MMAKE) $(MMAKEFLAGS) clean) \
 	fi
 
 realclean: realclean_tests realclean_subdirs realclean_local
 	+cd scripts; $(SUBDIR_MMAKE) realclean
 
+.PHONY: clean_extras
+clean_extras:
+	+if test -d extras; then \
+		(cd extras; $(MMAKE) $(MMAKEFLAGS) clean) \
+	fi
+
 .PHONY: realclean_local
-realclean_local: realclean_config realclean_docs
+realclean_local: realclean_config realclean_docs realclean_extras
 
 .PHONY: realclean_subdirs
 realclean_subdirs: clean_subdirs
@@ -970,7 +976,13 @@ realclean_config:
 .PHONY: realclean_tests
 realclean_tests:
 	+if test -d tests; then \
-		(cd tests; $(SUBDIR_MMAKE) realclean) \
+		(cd tests; $(MMAKE) $(MMAKEFLAGS) realclean) \
+	fi
+
+.PHONY: realclean_extras
+realclean_extras:
+	+if test -d extras; then \
+		(cd extras; $(MMAKE) $(MMAKEFLAGS) realclean) \
 	fi
 
 #-----------------------------------------------------------------------------#
diff --git a/configure.ac b/configure.ac
index 40f7b6e4b..dc9551305 100644
--- a/configure.ac
+++ b/configure.ac
@@ -5677,17 +5677,6 @@ AC_SUBST(CSHPATH)
 
 #-----------------------------------------------------------------------------#
 
-# When running the debugger tests we want to use the local mdbrc file,
-# not the installed one, so that we can test changes to this file
-# without having to install first. We therefore create a copy of the mdbrc.in
-# for use with the test suite.
-
-test_mdbrc=tests/mdbrc
-
-cat "`pwd`"/scripts/mdbrc.in | sed \
-    -e 's/DEFAULT_MERCURY_DEBUGGER_INIT_DIR/TESTS_MDB_INIT_DIR/g' \
-    -e 's/DEFAULT_MERCURY_DEBUGGER_DOC/TESTS_MDB_DOC/g' > $test_mdbrc.in
-
 TESTS_MDB_INIT_DIR="`pwd`"/scripts
 TESTS_MDB_DOC="`pwd`"/doc/mdb_doc
 AC_SUBST(TESTS_MDB_INIT_DIR)
@@ -5774,7 +5763,6 @@ output_files="$nonexecutable_output_files $executable_output_files"
 # scripts/mercury_config.in.
 
 AC_OUTPUT($output_files
-"$test_mdbrc"
 ,
 [
 # Only do this when compiling the source, not when reconfiguring
diff --git a/scripts/Mmakefile b/scripts/Mmakefile
index 13d17d11c..e46e9899f 100644
--- a/scripts/Mmakefile
+++ b/scripts/Mmakefile
@@ -48,22 +48,23 @@ CONF_FILES = \
 	Mmake.vars \
 	parse_ml_options.sh-subr
 
-CONF_DEBUG_SCRIPTS = 	\
+CONF_DEBUG_SCRIPTS = \
 	mdbrc
 
-DEBUGGER_SCRIPTS = $(CONF_DEBUG_SCRIPTS) 	\
-		xul_tree.xsl			\
-		mdb_open			\
-		mdb_grep			\
-		mdb_track			\
-		mdb_term_browser.js		\
-		mdb_term_browser.css		\
-		jquery.slim.js			\
-		jstree.js			\
-		jstree.style.css		\
-		32px.png			\
-		40px.png			\
-		throbber.gif
+DEBUGGER_SCRIPTS = \
+	$(CONF_DEBUG_SCRIPTS) \
+	xul_tree.xsl \
+	mdb_open \
+	mdb_grep \
+	mdb_track \
+	mdb_term_browser.js \
+	mdb_term_browser.css \
+	jquery.slim.js \
+	jstree.js \
+	jstree.style.css \
+	32px.png \
+	40px.png \
+	throbber.gif
 
 EMACS_SCRIPTS = gud.el
 
@@ -78,7 +79,7 @@ CSHARP_WRAPPER_SCRIPTS = \
 
 # .SUFFIXES: .in
 
-# we test membership of CONF_SCRIPTS and CONF_FILES, because testing $(@D)
+# We test membership of CONF_SCRIPTS and CONF_FILES, because testing $(@D)
 # (the directory part of $*) does the wrong thing for Mercury.config.
 # Not testing anything would make this rule apply even to ../Mmake.common.
 # The grep is there to ensure that there were no mispelt autoconf variable
@@ -105,10 +106,30 @@ CSHARP_WRAPPER_SCRIPTS = \
 		fi \
 	done
 
+# To allow a change to the debugger and/or to its documentation to be
+# matched by changes in the expected output files in the debugger and
+# declarative_debugger test directories, we must give the tests in those
+# directories access to mdb_doc and mdbrc files in the current workspace,
+# *not* in the installed system.
+test_mdbrc: mdbrc.in mdbrc
+	ABS_MERCURY_DIR=`(cd $(MERCURY_DIR); /bin/pwd)` ; \
+	sed \
+		-e "s:@DEFAULT_MERCURY_DEBUGGER_DOC@:$${ABS_MERCURY_DIR}/doc/mdb_doc:" \
+		-e "s:@DEFAULT_MERCURY_DEBUGGER_INIT_DIR@:$${ABS_MERCURY_DIR}/scripts:" \
+		-e '/^xml_/d' \
+		-e '/^web_/d' \
+	< mdbrc.in > test_mdbrc
+	egrep '^xml_' < mdbrc >> test_mdbrc
+	egrep '^web_' < mdbrc >> test_mdbrc
+	@if grep '@' test_mdbrc; then \
+		echo "unhandled configuration variable in test_mdbrc"; \
+		exit 1; \
+	fi
+
 #-----------------------------------------------------------------------------#
 
 .PHONY: all
-all: $(CONF_FILES) $(SCRIPTS) $(DEBUGGER_SCRIPTS) $(EMACS_SCRIPTS)
+all: $(CONF_FILES) $(SCRIPTS) $(DEBUGGER_SCRIPTS) $(EMACS_SCRIPTS) test_mdbrc
 
 #-----------------------------------------------------------------------------#
 
@@ -171,11 +192,9 @@ install_config: Mercury.config install_dirs
 
 .PHONY: install_debugger_scripts
 install_debugger_scripts: $(DEBUGGER_SCRIPTS) install_dirs
-	# Reportedly old versions of Mercury
-	# used to install mdbrc as read-only.
-	# If that is the case, then we need to make sure
-	# that it gets made writable before we install the
-	# new version.
+	# Reportedly old versions of Mercury used to install mdbrc
+	# as read-only. If that is the case, then we need to make sure
+	# that it gets made writable before we install the new version.
 	-chmod u+w $(INSTALL_LIBDIR)/mdb/*
 	cp $(DEBUGGER_SCRIPTS) $(INSTALL_LIBDIR)/mdb
 
diff --git a/tests/Mmake.common b/tests/Mmake.common
index 83b04d8f7..e66466172 100644
--- a/tests/Mmake.common
+++ b/tests/Mmake.common
@@ -82,7 +82,7 @@ JAVA=java
 # the source of irrelevant difference between the actual and expected outputs.
 
 MDB = HOME=/nonexistent MERCURY_SUPPRESS_MDB_BANNER=yes \
-	MERCURY_DEBUGGER_INIT=$(TESTS_DIR)/mdbrc mdb
+	MERCURY_DEBUGGER_INIT=$(WORKSPACE)/scripts/test_mdbrc mdb
 
 MDB_NOINIT = HOME=/nonexistent MERCURY_SUPPRESS_MDB_BANNER=yes \
 	MERCURY_DEBUGGER_INIT="" mdb
@@ -274,6 +274,10 @@ realclean_local: clean_logs clean_errors clean_mdbrc
 
 clean_local: clean_out clean_res clean_trace_counts clean_mdbrc_in
 
+# XXX As of 2020 oct 4, mdbrc and mdbrc.in are no longer created
+# in this directory. After a few weeks, after all workspaces can be
+# expected to be cleaned up, we should delete these two now-redundant
+# targets, and the references to them.
 clean_mdbrc:
 	-rm -f mdbrc
 
diff --git a/tests/Mmakefile b/tests/Mmakefile
index 18c76bd40..c337900dc 100644
--- a/tests/Mmakefile
+++ b/tests/Mmakefile
@@ -91,6 +91,10 @@ $(RUNTESTS_IN_SUBDIRS): runtests_in_%:
 		echo Could not run tests in directory $* >> NOMAKE_DIRS ; \
 	fi
 
+#-----------------------------------------------------------------------------#
+
+realclean: realclean_subdirs
+
 realclean_subdirs:
 	+succeeded=true; \
 	for dir in $(SUBDIRS); do \
@@ -102,6 +106,8 @@ realclean_subdirs:
 			;; \
 	esac
 
+clean: clean_subdirs
+
 clean_subdirs:
 	+succeeded=true; \
 	for dir in $(SUBDIRS); do \
@@ -112,3 +118,5 @@ clean_subdirs:
 			exit 1 \
 			;; \
 	esac
+
+#-----------------------------------------------------------------------------#
diff --git a/tools/bootcheck b/tools/bootcheck
index 33239044f..4566dbdca 100755
--- a/tools/bootcheck
+++ b/tools/bootcheck
@@ -1912,30 +1912,14 @@ if ${runtests}
 then
     echo "starting the test suite at `date`"
 
-    # We need to give tests/debugger access to the mdbrc and mdb_doc
-    # files in the doc and scripts directories, without hardcoding their
-    # pathnames. We must also compensate for scripts/mdbrc having hardcoded
-    # within it the *installed* pathname of mdb_doc and not its current
-    # pathname.
-    cat ${root}/doc/mdb_doc > ${root}/scripts/test_mdbrc
-    sed -e '/^source/d' ${root}/scripts/mdbrc >> ${root}/scripts/test_mdbrc
+    # If the workspace has been moved since ${root}/scripts/test_mdbrc
+    # was last built, that file will refer to the OLD location of
+    # the workspace, which may not exist anymore. We therefore rebuild
+    # the file.
+    (cd =${root}/scripts; /bin/rm test_mdbrc; mmake test_mdbrc)
     MERCURY_DEBUGGER_INIT=${root}/scripts/test_mdbrc
     export MERCURY_DEBUGGER_INIT
 
-    # If the workspace has been copied or moved since ${root}/tests/mdbrc
-    # has been created by an invocation of ${root}/configure, the
-    # ${root}/tests/mdbrc file will refer to the mdb_doc file in the OLD
-    # location of the workspace, which may not exist anymore.
-    # Override the settings in tests/mdbrc that refer to the current
-    # directory; keep the xml settings, which do not do so.
-    sed \
-        -e "s:@TESTS_MDB_DOC@:${root}/doc/mdb_doc:" \
-        -e "s:@TESTS_MDB_INIT_DIR@:${root}/scripts:" \
-        -e "/^xml_/d" \
-        < "${root}/tests/mdbrc.in" > "${root}/tests/mdbrc.tmp"
-    grep '^xml_' < "${root}/tests/mdbrc" >> "${root}/tests/mdbrc.tmp"
-    mv "${root}/tests/mdbrc.tmp" "${root}/tests/mdbrc"
-
     MERCURY_SUPPRESS_STACK_TRACE=yes
     export MERCURY_SUPPRESS_STACK_TRACE