a Makefile target for test coverage

Makefile.am

@@ -10,5 +10,12 @@ json98_CXXFLAGS = -std=c++98
 json98_CPPFLAGS = -I$(top_srcdir)/src
 
 svn-clean: maintainer-clean
-	rm -fr configure INSTALL aclocal.m4 build-aux depcomp install-sh missing test-driver
+	rm -fr configure INSTALL aclocal.m4 build-aux depcomp install-sh missing test-driver cover_html *.gcda *.gcno coverage*.info
 	for DIR in $(DIST_SUBDIRS) .; do rm -f $$DIR/Makefile.in; done
+
+cover:
+	make clean
+	make json98 CXXFLAGS+="--coverage -g -fprofile-arcs -ftest-coverage" CPPFLAGS+="-DNDEBUG"
+	./json98
+	lcov --capture --directory . --output-file coverage98.info
+	genhtml coverage*.info --output-directory cover_html --show-details --title "$(PACKAGE_STRING)" --legend --demangle-cpp