diff --git a/m4/ax_valgrind_check.m4 b/m4/ax_valgrind_check.m4
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+# ===========================================================================
+#    https://www.gnu.org/software/autoconf-archive/ax_valgrind_check.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_VALGRIND_DFLT(memcheck|helgrind|drd|sgcheck, on|off)
+#   AX_VALGRIND_CHECK()
+#
+# DESCRIPTION
+#
+#   AX_VALGRIND_CHECK checks whether Valgrind is present and, if so, allows
+#   running `make check` under a variety of Valgrind tools to check for
+#   memory and threading errors.
+#
+#   Defines VALGRIND_CHECK_RULES which should be substituted in your
+#   Makefile; and $enable_valgrind which can be used in subsequent configure
+#   output. VALGRIND_ENABLED is defined and substituted, and corresponds to
+#   the value of the --enable-valgrind option, which defaults to being
+#   enabled if Valgrind is installed and disabled otherwise. Individual
+#   Valgrind tools can be disabled via --disable-valgrind-<tool>, the
+#   default is configurable via the AX_VALGRIND_DFLT command or is to use
+#   all commands not disabled via AX_VALGRIND_DFLT. All AX_VALGRIND_DFLT
+#   calls must be made before the call to AX_VALGRIND_CHECK.
+#
+#   If unit tests are written using a shell script and automake's
+#   LOG_COMPILER system, the $(VALGRIND) variable can be used within the
+#   shell scripts to enable Valgrind, as described here:
+#
+#     https://www.gnu.org/software/gnulib/manual/html_node/Running-self_002dtests-under-valgrind.html
+#
+#   Usage example:
+#
+#   configure.ac:
+#
+#     AX_VALGRIND_DFLT([sgcheck], [off])
+#     AX_VALGRIND_CHECK
+#
+#   in each Makefile.am with tests:
+#
+#     @VALGRIND_CHECK_RULES@
+#     VALGRIND_SUPPRESSIONS_FILES = my-project.supp
+#     EXTRA_DIST = my-project.supp
+#
+#   This results in a "check-valgrind" rule being added. Running `make
+#   check-valgrind` in that directory will recursively run the module's test
+#   suite (`make check`) once for each of the available Valgrind tools (out
+#   of memcheck, helgrind and drd) while the sgcheck will be skipped unless
+#   enabled again on the commandline with --enable-valgrind-sgcheck. The
+#   results for each check will be output to test-suite-$toolname.log. The
+#   target will succeed if there are zero errors and fail otherwise.
+#
+#   Alternatively, a "check-valgrind-$TOOL" rule will be added, for $TOOL in
+#   memcheck, helgrind, drd and sgcheck. These are useful because often only
+#   some of those tools can be ran cleanly on a codebase.
+#
+#   The macro supports running with and without libtool.
+#
+# LICENSE
+#
+#   Copyright (c) 2014, 2015, 2016 Philip Withnall <philip.withnall@collabora.co.uk>
+#
+#   Copying and distribution of this file, with or without modification, are
+#   permitted in any medium without royalty provided the copyright notice
+#   and this notice are preserved.  This file is offered as-is, without any
+#   warranty.
+
+#serial 23
+
+dnl Configured tools
+m4_define([valgrind_tool_list], [[memcheck], [helgrind], [drd], [sgcheck]])
+m4_set_add_all([valgrind_exp_tool_set], [sgcheck])
+m4_foreach([vgtool], [valgrind_tool_list],
+           [m4_define([en_dflt_valgrind_]vgtool, [on])])
+
+AC_DEFUN([AX_VALGRIND_DFLT],[
+	m4_define([en_dflt_valgrind_$1], [$2])
+])dnl
+
+AC_DEFUN([AX_VALGRIND_CHECK],[
+	AM_EXTRA_RECURSIVE_TARGETS([check-valgrind])
+	m4_foreach([vgtool], [valgrind_tool_list],
+		[AM_EXTRA_RECURSIVE_TARGETS([check-valgrind-]vgtool)])
+
+	dnl Check for --enable-valgrind
+	AC_ARG_ENABLE([valgrind],
+	              [AS_HELP_STRING([--enable-valgrind], [Whether to enable Valgrind on the unit tests])],
+	              [enable_valgrind=$enableval],[enable_valgrind=])
+
+	AS_IF([test "$enable_valgrind" != "no"],[
+		# Check for Valgrind.
+		AC_CHECK_PROG([VALGRIND],[valgrind],[valgrind])
+		AS_IF([test "$VALGRIND" = ""],[
+			AS_IF([test "$enable_valgrind" = "yes"],[
+				AC_MSG_ERROR([Could not find valgrind; either install it or reconfigure with --disable-valgrind])
+			],[
+				enable_valgrind=no
+			])
+		],[
+			enable_valgrind=yes
+		])
+	])
+
+	AM_CONDITIONAL([VALGRIND_ENABLED],[test "$enable_valgrind" = "yes"])
+	AC_SUBST([VALGRIND_ENABLED],[$enable_valgrind])
+
+	# Check for Valgrind tools we care about.
+	[valgrind_enabled_tools=]
+	m4_foreach([vgtool],[valgrind_tool_list],[
+		AC_ARG_ENABLE([valgrind-]vgtool,
+		    m4_if(m4_defn([en_dflt_valgrind_]vgtool),[off],dnl
+[AS_HELP_STRING([--enable-valgrind-]vgtool, [Whether to use ]vgtool[ during the Valgrind tests])],dnl
+[AS_HELP_STRING([--disable-valgrind-]vgtool, [Whether to skip ]vgtool[ during the Valgrind tests])]),
+		              [enable_valgrind_]vgtool[=$enableval],
+		              [enable_valgrind_]vgtool[=])
+		AS_IF([test "$enable_valgrind" = "no"],[
+			enable_valgrind_]vgtool[=no],
+		      [test "$enable_valgrind_]vgtool[" ]dnl
+m4_if(m4_defn([en_dflt_valgrind_]vgtool), [off], [= "yes"], [!= "no"]),[
+			AC_CACHE_CHECK([for Valgrind tool ]vgtool,
+			               [ax_cv_valgrind_tool_]vgtool,[
+				ax_cv_valgrind_tool_]vgtool[=no
+				m4_set_contains([valgrind_exp_tool_set],vgtool,
+				    [m4_define([vgtoolx],[exp-]vgtool)],
+				    [m4_define([vgtoolx],vgtool)])
+				AS_IF([`$VALGRIND --tool=]vgtoolx[ --help >/dev/null 2>&1`],[
+					ax_cv_valgrind_tool_]vgtool[=yes
+				])
+			])
+			AS_IF([test "$ax_cv_valgrind_tool_]vgtool[" = "no"],[
+				AS_IF([test "$enable_valgrind_]vgtool[" = "yes"],[
+					AC_MSG_ERROR([Valgrind does not support ]vgtool[; reconfigure with --disable-valgrind-]vgtool)
+				],[
+					enable_valgrind_]vgtool[=no
+				])
+			],[
+				enable_valgrind_]vgtool[=yes
+			])
+		])
+		AS_IF([test "$enable_valgrind_]vgtool[" = "yes"],[
+			valgrind_enabled_tools="$valgrind_enabled_tools ]m4_bpatsubst(vgtool,[^exp-])["
+		])
+		AC_SUBST([ENABLE_VALGRIND_]vgtool,[$enable_valgrind_]vgtool)
+	])
+	AC_SUBST([valgrind_tools],["]m4_join([ ], valgrind_tool_list)["])
+	AC_SUBST([valgrind_enabled_tools],[$valgrind_enabled_tools])
+
+[VALGRIND_CHECK_RULES='
+# Valgrind check
+#
+# Optional:
+#  - VALGRIND_SUPPRESSIONS_FILES: Space-separated list of Valgrind suppressions
+#    files to load. (Default: empty)
+#  - VALGRIND_FLAGS: General flags to pass to all Valgrind tools.
+#    (Default: --num-callers=30)
+#  - VALGRIND_$toolname_FLAGS: Flags to pass to Valgrind $toolname (one of:
+#    memcheck, helgrind, drd, sgcheck). (Default: various)
+
+# Optional variables
+VALGRIND_SUPPRESSIONS ?= $(addprefix --suppressions=,$(VALGRIND_SUPPRESSIONS_FILES))
+VALGRIND_FLAGS ?= --num-callers=30
+VALGRIND_memcheck_FLAGS ?= --leak-check=full --show-reachable=no
+VALGRIND_helgrind_FLAGS ?= --history-level=approx
+VALGRIND_drd_FLAGS ?=
+VALGRIND_sgcheck_FLAGS ?=
+
+# Internal use
+valgrind_log_files = $(addprefix test-suite-,$(addsuffix .log,$(valgrind_tools)))
+
+valgrind_memcheck_flags = --tool=memcheck $(VALGRIND_memcheck_FLAGS)
+valgrind_helgrind_flags = --tool=helgrind $(VALGRIND_helgrind_FLAGS)
+valgrind_drd_flags = --tool=drd $(VALGRIND_drd_FLAGS)
+valgrind_sgcheck_flags = --tool=exp-sgcheck $(VALGRIND_sgcheck_FLAGS)
+
+valgrind_quiet = $(valgrind_quiet_$(V))
+valgrind_quiet_ = $(valgrind_quiet_$(AM_DEFAULT_VERBOSITY))
+valgrind_quiet_0 = --quiet
+valgrind_v_use   = $(valgrind_v_use_$(V))
+valgrind_v_use_  = $(valgrind_v_use_$(AM_DEFAULT_VERBOSITY))
+valgrind_v_use_0 = @echo "  USE   " $(patsubst check-valgrind-%-local,%,$''@):;
+
+# Support running with and without libtool.
+ifneq ($(LIBTOOL),)
+valgrind_lt = $(LIBTOOL) $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=execute
+else
+valgrind_lt =
+endif
+
+# Use recursive makes in order to ignore errors during check
+check-valgrind-local:
+ifeq ($(VALGRIND_ENABLED),yes)
+	$(A''M_V_at)$(MAKE) $(AM_MAKEFLAGS) -k \
+		$(foreach tool, $(valgrind_enabled_tools), check-valgrind-$(tool))
+else
+	@echo "Need to reconfigure with --enable-valgrind"
+endif
+
+# Valgrind running
+VALGRIND_TESTS_ENVIRONMENT = \
+	$(TESTS_ENVIRONMENT) \
+	env VALGRIND=$(VALGRIND) \
+	G_SLICE=always-malloc,debug-blocks \
+	G_DEBUG=fatal-warnings,fatal-criticals,gc-friendly
+
+VALGRIND_LOG_COMPILER = \
+	$(valgrind_lt) \
+	$(VALGRIND) $(VALGRIND_SUPPRESSIONS) --error-exitcode=1 $(VALGRIND_FLAGS)
+
+define valgrind_tool_rule
+check-valgrind-$(1)-local:
+ifeq ($$(VALGRIND_ENABLED)-$$(ENABLE_VALGRIND_$(1)),yes-yes)
+ifneq ($$(TESTS),)
+	$$(valgrind_v_use)$$(MAKE) check-TESTS \
+		TESTS_ENVIRONMENT="$$(VALGRIND_TESTS_ENVIRONMENT)" \
+		LOG_COMPILER="$$(VALGRIND_LOG_COMPILER)" \
+		LOG_FLAGS="$$(valgrind_$(1)_flags)" \
+		TEST_SUITE_LOG=test-suite-$(1).log
+endif
+else ifeq ($$(VALGRIND_ENABLED),yes)
+	@echo "Need to reconfigure with --enable-valgrind-$(1)"
+else
+	@echo "Need to reconfigure with --enable-valgrind"
+endif
+endef
+
+$(foreach tool,$(valgrind_tools),$(eval $(call valgrind_tool_rule,$(tool))))
+
+A''M_DISTCHECK_CONFIGURE_FLAGS ?=
+A''M_DISTCHECK_CONFIGURE_FLAGS += --disable-valgrind
+
+MOSTLYCLEANFILES ?=
+MOSTLYCLEANFILES += $(valgrind_log_files)
+
+.PHONY: check-valgrind $(addprefix check-valgrind-,$(valgrind_tools))
+']
+
+	AC_SUBST([VALGRIND_CHECK_RULES])
+	m4_ifdef([_AM_SUBST_NOTMAKE], [_AM_SUBST_NOTMAKE([VALGRIND_CHECK_RULES])])
+])