diff --git a/m4/ax_code_coverage.m4 b/m4/ax_code_coverage.m4
index 67b2774b4..6484f0332 100644
--- a/m4/ax_code_coverage.m4
+++ b/m4/ax_code_coverage.m4
@@ -1,5 +1,5 @@
 # ===========================================================================
-#     http://www.gnu.org/software/autoconf-archive/ax_code_coverage.html
+#     https://www.gnu.org/software/autoconf-archive/ax_code_coverage.html
 # ===========================================================================
 #
 # SYNOPSIS
@@ -8,19 +8,20 @@
 #
 # DESCRIPTION
 #
-#   Defines CODE_COVERAGE_CFLAGS and CODE_COVERAGE_LDFLAGS which should be
-#   included in the CFLAGS and LIBS/LDFLAGS variables of every build target
-#   (program or library) which should be built with code coverage support.
-#   Also defines CODE_COVERAGE_RULES which should be substituted in your
-#   Makefile; and $enable_code_coverage which can be used in subsequent
-#   configure output. CODE_COVERAGE_ENABLED is defined and substituted, and
-#   corresponds to the value of the --enable-code-coverage option, which
-#   defaults to being disabled.
+#   Defines CODE_COVERAGE_CPPFLAGS, CODE_COVERAGE_CFLAGS,
+#   CODE_COVERAGE_CXXFLAGS and CODE_COVERAGE_LIBS which should be included
+#   in the CPPFLAGS, CFLAGS CXXFLAGS and LIBS/LIBADD variables of every
+#   build target (program or library) which should be built with code
+#   coverage support. Also defines CODE_COVERAGE_RULES which should be
+#   substituted in your Makefile; and $enable_code_coverage which can be
+#   used in subsequent configure output. CODE_COVERAGE_ENABLED is defined
+#   and substituted, and corresponds to the value of the
+#   --enable-code-coverage option, which defaults to being disabled.
 #
 #   Test also for gcov program and create GCOV variable that could be
 #   substituted.
 #
-#   Note that all optimisation flags in CFLAGS must be disabled when code
+#   Note that all optimization flags in CFLAGS must be disabled when code
 #   coverage is enabled.
 #
 #   Usage example:
@@ -32,8 +33,10 @@
 #   Makefile.am:
 #
 #     @CODE_COVERAGE_RULES@
-#     my_program_LIBS = ... $(CODE_COVERAGE_LDFLAGS) ...
+#     my_program_LIBS = ... $(CODE_COVERAGE_LIBS) ...
+#     my_program_CPPFLAGS = ... $(CODE_COVERAGE_CPPFLAGS) ...
 #     my_program_CFLAGS = ... $(CODE_COVERAGE_CFLAGS) ...
+#     my_program_CXXFLAGS = ... $(CODE_COVERAGE_CXXFLAGS) ...
 #
 #   This results in a "check-code-coverage" rule being added to any
 #   Makefile.am which includes "@CODE_COVERAGE_RULES@" (assuming the module
@@ -42,12 +45,17 @@
 #   (`make check`) and build a code coverage report detailing the code which
 #   was touched, then print the URI for the report.
 #
+#   In earlier versions of this macro, CODE_COVERAGE_LDFLAGS was defined
+#   instead of CODE_COVERAGE_LIBS. They are both still defined, but use of
+#   CODE_COVERAGE_LIBS is preferred for clarity; CODE_COVERAGE_LDFLAGS is
+#   deprecated. They have the same value.
+#
 #   This code was derived from Makefile.decl in GLib, originally licenced
 #   under LGPLv2.1+.
 #
 # LICENSE
 #
-#   Copyright (c) 2012 Philip Withnall
+#   Copyright (c) 2012, 2016 Philip Withnall
 #   Copyright (c) 2012 Xan Lopez
 #   Copyright (c) 2012 Christian Persch
 #   Copyright (c) 2012 Paolo Borelli
@@ -65,9 +73,9 @@
 #   General Public License for more details.
 #
 #   You should have received a copy of the GNU Lesser General Public License
-#   along with this program. If not, see <http://www.gnu.org/licenses/>.
+#   along with this program. If not, see <https://www.gnu.org/licenses/>.
 
-#serial 5
+#serial 25
 
 AC_DEFUN([AX_CODE_COVERAGE],[
 	dnl Check for --enable-code-coverage
@@ -103,51 +111,64 @@ AC_DEFUN([AX_CODE_COVERAGE],[
 			AC_MSG_ERROR([not compiling with gcc, which is required for gcov code coverage])
 		])
 
-		# List of supported lcov versions.
-		lcov_version_list="1.6 1.7 1.8 1.9 1.10 1.11 1.13"
-
 		AC_CHECK_PROG([LCOV], [lcov], [lcov])
 		AC_CHECK_PROG([GENHTML], [genhtml], [genhtml])
 
-		AS_IF([ test "$LCOV" ], [
-			AC_CACHE_CHECK([for lcov version], ax_cv_lcov_version, [
-				ax_cv_lcov_version=invalid
-				lcov_version=`$LCOV -v 2>/dev/null | $SED -e 's/^.* //'`
-				for lcov_check_version in $lcov_version_list; do
-					if test "$lcov_version" = "$lcov_check_version"; then
-						ax_cv_lcov_version="$lcov_check_version (ok)"
-					fi
-				done
-			])
-		], [
-			lcov_msg="To enable code coverage reporting you must have one of the following lcov versions installed: $lcov_version_list"
-			AC_MSG_ERROR([$lcov_msg])
+		AS_IF([ test -z "$LCOV" ], [
+			AC_MSG_ERROR([To enable code coverage reporting you must have lcov installed])
 		])
 
-		case $ax_cv_lcov_version in
-			""|invalid[)]
-				lcov_msg="You must have one of the following versions of lcov: $lcov_version_list (found: $lcov_version)."
-				AC_MSG_ERROR([$lcov_msg])
-				LCOV="exit 0;"
-			;;
-		esac
-
 		AS_IF([ test -z "$GENHTML" ], [
 			AC_MSG_ERROR([Could not find genhtml from the lcov package])
 		])
 
 		dnl Build the code coverage flags
+		dnl Define CODE_COVERAGE_LDFLAGS for backwards compatibility
+		CODE_COVERAGE_CPPFLAGS="-DNDEBUG"
 		CODE_COVERAGE_CFLAGS="-O0 -g -fprofile-arcs -ftest-coverage"
-		CODE_COVERAGE_LDFLAGS="-lgcov"
+		CODE_COVERAGE_CXXFLAGS="-O0 -g -fprofile-arcs -ftest-coverage"
+		CODE_COVERAGE_LIBS="-lgcov"
+		CODE_COVERAGE_LDFLAGS="$CODE_COVERAGE_LIBS"
 
+		AC_SUBST([CODE_COVERAGE_CPPFLAGS])
 		AC_SUBST([CODE_COVERAGE_CFLAGS])
+		AC_SUBST([CODE_COVERAGE_CXXFLAGS])
+		AC_SUBST([CODE_COVERAGE_LIBS])
 		AC_SUBST([CODE_COVERAGE_LDFLAGS])
 
-CODE_COVERAGE_RULES='
+		[CODE_COVERAGE_RULES_CHECK='
+	-$(A''M_V_at)$(MAKE) $(AM_MAKEFLAGS) -k check
+	$(A''M_V_at)$(MAKE) $(AM_MAKEFLAGS) code-coverage-capture
+']
+		[CODE_COVERAGE_RULES_CAPTURE='
+	$(code_coverage_v_lcov_cap)$(LCOV) $(code_coverage_quiet) $(addprefix --directory ,$(CODE_COVERAGE_DIRECTORY)) --capture --output-file "$(CODE_COVERAGE_OUTPUT_FILE).tmp" --test-name "$(call code_coverage_sanitize,$(PACKAGE_NAME)-$(PACKAGE_VERSION))" --no-checksum --compat-libtool $(CODE_COVERAGE_LCOV_SHOPTS) $(CODE_COVERAGE_LCOV_OPTIONS)
+	$(code_coverage_v_lcov_ign)$(LCOV) $(code_coverage_quiet) $(addprefix --directory ,$(CODE_COVERAGE_DIRECTORY)) --remove "$(CODE_COVERAGE_OUTPUT_FILE).tmp" "/tmp/*" $(CODE_COVERAGE_IGNORE_PATTERN) --output-file "$(CODE_COVERAGE_OUTPUT_FILE)" $(CODE_COVERAGE_LCOV_SHOPTS) $(CODE_COVERAGE_LCOV_RMOPTS)
+	-@rm -f $(CODE_COVERAGE_OUTPUT_FILE).tmp
+	$(code_coverage_v_genhtml)LANG=C $(GENHTML) $(code_coverage_quiet) $(addprefix --prefix ,$(CODE_COVERAGE_DIRECTORY)) --output-directory "$(CODE_COVERAGE_OUTPUT_DIRECTORY)" --title "$(PACKAGE_NAME)-$(PACKAGE_VERSION) Code Coverage" --legend --show-details "$(CODE_COVERAGE_OUTPUT_FILE)" $(CODE_COVERAGE_GENHTML_OPTIONS)
+	@echo "file://$(abs_builddir)/$(CODE_COVERAGE_OUTPUT_DIRECTORY)/index.html"
+']
+		[CODE_COVERAGE_RULES_CLEAN='
+clean: code-coverage-clean
+distclean: code-coverage-clean
+code-coverage-clean:
+	-$(LCOV) --directory $(top_builddir) -z
+	-rm -rf $(CODE_COVERAGE_OUTPUT_FILE) $(CODE_COVERAGE_OUTPUT_FILE).tmp $(CODE_COVERAGE_OUTPUT_DIRECTORY)
+	-find . \( -name "*.gcda" -o -name "*.gcno" -o -name "*.gcov" \) -delete
+']
+	], [
+		[CODE_COVERAGE_RULES_CHECK='
+	@echo "Need to reconfigure with --enable-code-coverage"
+']
+		CODE_COVERAGE_RULES_CAPTURE="$CODE_COVERAGE_RULES_CHECK"
+		CODE_COVERAGE_RULES_CLEAN=''
+	])
+
+[CODE_COVERAGE_RULES='
 # Code coverage
 #
 # Optional:
 #  - CODE_COVERAGE_DIRECTORY: Top-level directory for code coverage reporting.
+#    Multiple directories may be specified, separated by whitespace.
 #    (Default: $(top_builddir))
 #  - CODE_COVERAGE_OUTPUT_FILE: Filename and path for the .info file generated
 #    by lcov for code coverage. (Default:
@@ -155,13 +176,26 @@ CODE_COVERAGE_RULES='
 #  - CODE_COVERAGE_OUTPUT_DIRECTORY: Directory for generated code coverage
 #    reports to be created. (Default:
 #    $(PACKAGE_NAME)-$(PACKAGE_VERSION)-coverage)
+#  - CODE_COVERAGE_BRANCH_COVERAGE: Set to 1 to enforce branch coverage,
+#    set to 0 to disable it and leave empty to stay with the default.
+#    (Default: empty)
+#  - CODE_COVERAGE_LCOV_SHOPTS_DEFAULT: Extra options shared between both lcov
+#    instances. (Default: based on $CODE_COVERAGE_BRANCH_COVERAGE)
+#  - CODE_COVERAGE_LCOV_SHOPTS: Extra options to shared between both lcov
+#    instances. (Default: $CODE_COVERAGE_LCOV_SHOPTS_DEFAULT)
 #  - CODE_COVERAGE_LCOV_OPTIONS_GCOVPATH: --gcov-tool pathtogcov
-#  - CODE_COVERAGE_LCOV_OPTIONS_DEFAULT: Extra options to pass to the lcov instance.
-#    (Default: $CODE_COVERAGE_LCOV_OPTIONS_GCOVPATH)
-#  - CODE_COVERAGE_LCOV_OPTIONS: Extra options to pass to the lcov instance.
-#    (Default: $CODE_COVERAGE_LCOV_OPTIONS_DEFAULT)
+#  - CODE_COVERAGE_LCOV_OPTIONS_DEFAULT: Extra options to pass to the
+#    collecting lcov instance. (Default: $CODE_COVERAGE_LCOV_OPTIONS_GCOVPATH)
+#  - CODE_COVERAGE_LCOV_OPTIONS: Extra options to pass to the collecting lcov
+#    instance. (Default: $CODE_COVERAGE_LCOV_OPTIONS_DEFAULT)
+#  - CODE_COVERAGE_LCOV_RMOPTS_DEFAULT: Extra options to pass to the filtering
+#    lcov instance. (Default: empty)
+#  - CODE_COVERAGE_LCOV_RMOPTS: Extra options to pass to the filtering lcov
+#    instance. (Default: $CODE_COVERAGE_LCOV_RMOPTS_DEFAULT)
+#  - CODE_COVERAGE_GENHTML_OPTIONS_DEFAULT: Extra options to pass to the
+#    genhtml instance. (Default: based on $CODE_COVERAGE_BRANCH_COVERAGE)
 #  - CODE_COVERAGE_GENHTML_OPTIONS: Extra options to pass to the genhtml
-#    instance. (Default: empty)
+#    instance. (Default: $CODE_COVERAGE_GENHTML_OPTIONS_DEFAULT)
 #  - CODE_COVERAGE_IGNORE_PATTERN: Extra glob pattern of files to ignore
 #
 # The generated report will be titled using the $(PACKAGE_NAME) and
@@ -172,48 +206,59 @@ CODE_COVERAGE_RULES='
 CODE_COVERAGE_DIRECTORY ?= $(top_builddir)
 CODE_COVERAGE_OUTPUT_FILE ?= $(PACKAGE_NAME)-$(PACKAGE_VERSION)-coverage.info
 CODE_COVERAGE_OUTPUT_DIRECTORY ?= $(PACKAGE_NAME)-$(PACKAGE_VERSION)-coverage
+CODE_COVERAGE_BRANCH_COVERAGE ?=
+CODE_COVERAGE_LCOV_SHOPTS_DEFAULT ?= $(if $(CODE_COVERAGE_BRANCH_COVERAGE),\
+--rc lcov_branch_coverage=$(CODE_COVERAGE_BRANCH_COVERAGE))
+CODE_COVERAGE_LCOV_SHOPTS ?= $(CODE_COVERAGE_LCOV_SHOPTS_DEFAULT)
 CODE_COVERAGE_LCOV_OPTIONS_GCOVPATH ?= --gcov-tool "$(GCOV)"
 CODE_COVERAGE_LCOV_OPTIONS_DEFAULT ?= $(CODE_COVERAGE_LCOV_OPTIONS_GCOVPATH)
 CODE_COVERAGE_LCOV_OPTIONS ?= $(CODE_COVERAGE_LCOV_OPTIONS_DEFAULT)
-CODE_COVERAGE_GENHTML_OPTIONS ?=
+CODE_COVERAGE_LCOV_RMOPTS_DEFAULT ?=
+CODE_COVERAGE_LCOV_RMOPTS ?= $(CODE_COVERAGE_LCOV_RMOPTS_DEFAULT)
+CODE_COVERAGE_GENHTML_OPTIONS_DEFAULT ?=\
+$(if $(CODE_COVERAGE_BRANCH_COVERAGE),\
+--rc genhtml_branch_coverage=$(CODE_COVERAGE_BRANCH_COVERAGE))
+CODE_COVERAGE_GENHTML_OPTIONS ?= $(CODE_COVERAGE_GENHTML_OPTIONS_DEFAULT)
 CODE_COVERAGE_IGNORE_PATTERN ?=
 
-code_coverage_quiet = $(code_coverage_quiet_$(V))
-code_coverage_quiet_ =
-code_coverage_quiet_0 = --quiet
-
-# Use recursive makes in order to ignore errors during check
-check-code-coverage:
-	-$(MAKE) $(AM_MAKEFLAGS) -k check
-	$(MAKE) $(AM_MAKEFLAGS) code-coverage-capture
-
-# Capture code coverage data
-code-coverage-capture: code-coverage-capture-hook
-	$(LCOV) $(code_coverage_quiet) --directory $(CODE_COVERAGE_DIRECTORY) --capture --output-file "$(CODE_COVERAGE_OUTPUT_FILE).tmp" --test-name "$(PACKAGE_NAME)-$(PACKAGE_VERSION)" --no-checksum --compat-libtool $(CODE_COVERAGE_LCOV_OPTIONS)
-	$(LCOV) $(code_coverage_quiet) --directory $(CODE_COVERAGE_DIRECTORY) --remove "$(CODE_COVERAGE_OUTPUT_FILE).tmp" "/tmp/*" $(CODE_COVERAGE_IGNORE_PATTERN) --output-file "$(CODE_COVERAGE_OUTPUT_FILE)"
-	-@rm -f $(CODE_COVERAGE_OUTPUT_FILE).tmp
-	LANG=C $(GENHTML) $(code_coverage_quiet) --prefix $(CODE_COVERAGE_DIRECTORY) --output-directory "$(CODE_COVERAGE_OUTPUT_DIRECTORY)" --title "$(PACKAGE_NAME)-$(PACKAGE_VERSION) Code Coverage" --legend --show-details "$(CODE_COVERAGE_OUTPUT_FILE)" $(CODE_COVERAGE_GENHTML_OPTIONS)
-	@echo "file://$(abs_builddir)/$(CODE_COVERAGE_OUTPUT_DIRECTORY)/index.html"
-
-# Hook rule executed before code-coverage-capture, overridable by the user
-code-coverage-capture-hook:
-
-clean: code-coverage-clean
-code-coverage-clean:
-	-$(LCOV) --directory $(top_builddir) -z
-	-rm -rf $(CODE_COVERAGE_OUTPUT_FILE) $(CODE_COVERAGE_OUTPUT_FILE).tmp $(CODE_COVERAGE_OUTPUT_DIRECTORY)
-	-find . -name "*.gcda" -o -name "*.gcov" -delete
-
 GITIGNOREFILES ?=
 GITIGNOREFILES += $(CODE_COVERAGE_OUTPUT_FILE) $(CODE_COVERAGE_OUTPUT_DIRECTORY)
 
-DISTCHECK_CONFIGURE_FLAGS ?=
-DISTCHECK_CONFIGURE_FLAGS += --disable-code-coverage
+code_coverage_v_lcov_cap = $(code_coverage_v_lcov_cap_$(V))
+code_coverage_v_lcov_cap_ = $(code_coverage_v_lcov_cap_$(AM_DEFAULT_VERBOSITY))
+code_coverage_v_lcov_cap_0 = @echo "  LCOV   --capture"\
+ $(CODE_COVERAGE_OUTPUT_FILE);
+code_coverage_v_lcov_ign = $(code_coverage_v_lcov_ign_$(V))
+code_coverage_v_lcov_ign_ = $(code_coverage_v_lcov_ign_$(AM_DEFAULT_VERBOSITY))
+code_coverage_v_lcov_ign_0 = @echo "  LCOV   --remove /tmp/*"\
+ $(CODE_COVERAGE_IGNORE_PATTERN);
+code_coverage_v_genhtml = $(code_coverage_v_genhtml_$(V))
+code_coverage_v_genhtml_ = $(code_coverage_v_genhtml_$(AM_DEFAULT_VERBOSITY))
+code_coverage_v_genhtml_0 = @echo "  GEN   " $(CODE_COVERAGE_OUTPUT_DIRECTORY);
+code_coverage_quiet = $(code_coverage_quiet_$(V))
+code_coverage_quiet_ = $(code_coverage_quiet_$(AM_DEFAULT_VERBOSITY))
+code_coverage_quiet_0 = --quiet
+
+# sanitizes the test-name: replaces with underscores: dashes and dots
+code_coverage_sanitize = $(subst -,_,$(subst .,_,$(1)))
+
+# Use recursive makes in order to ignore errors during check
+check-code-coverage:'"$CODE_COVERAGE_RULES_CHECK"'
+
+# Capture code coverage data
+code-coverage-capture: code-coverage-capture-hook'"$CODE_COVERAGE_RULES_CAPTURE"'
+
+# Hook rule executed before code-coverage-capture, overridable by the user
+code-coverage-capture-hook:
+
+'"$CODE_COVERAGE_RULES_CLEAN"'
+
+A''M_DISTCHECK_CONFIGURE_FLAGS ?=
+A''M_DISTCHECK_CONFIGURE_FLAGS += --disable-code-coverage
 
 .PHONY: check-code-coverage code-coverage-capture code-coverage-capture-hook code-coverage-clean
-'
-	AC_SUBST([CODE_COVERAGE_RULES])
-	])
+']
 
+	AC_SUBST([CODE_COVERAGE_RULES])
 	m4_ifdef([_AM_SUBST_NOTMAKE], [_AM_SUBST_NOTMAKE([CODE_COVERAGE_RULES])])
 ])