Index: Makefile.in
==================================================================
--- Makefile.in
+++ Makefile.in
@@ -64,27 +64,40 @@
 	rm -f nano.tcl.h.new.1
 	mv nano.tcl.h.new.2 nano.tcl.h
 
 test: @EXTENSION_TARGET@ pkgIndex.tcl
 	@srcdir@/test/test.tcl .
+
+ifeq (@ENABLE_COVERAGE@,true)
+coverage.dir: test
+	rm -f nano-coverage.info
+	lcov --capture --directory . --output-file nano-coverage.info
+	mkdir coverage.dir
+	genhtml nano-coverage.info --output-directory coverage.dir
+	rm -f nano-coverage.info
+endif
 
 install: @EXTENSION_TARGET@ pkgIndex.tcl @srcdir@/nano.man
 	$(INSTALL) -d '$(DESTDIR)$(PACKAGE_INSTALL_DIR)'
 	$(INSTALL_PROGRAM) @EXTENSION_TARGET@ '$(DESTDIR)$(PACKAGE_INSTALL_DIR)'
 	$(INSTALL_DATA)    pkgIndex.tcl '$(DESTDIR)$(PACKAGE_INSTALL_DIR)'
 	$(INSTALL_DATA)    @srcdir@/nano.man '$(DESTDIR)$(PACKAGE_INSTALL_DIR)'
  
 clean:
 	rm -f nano-amalgamation.c nano-amalgamation.o
-	rm -f @EXTENSION_TARGET@ nano.o
+	rm -f @EXTENSION_TARGET@ nano.o nano.gcda nano.gcno
 	rm -f blake2b.o tweetnacl.o randombytes.o
+	rm -f blake2b.gcda tweetnacl.gcda randombytes.gcda
+	rm -f blake2b.gcno tweetnacl.gcno randombytes.gcno
+	rm -f nano-coverage.info
 
 distclean: clean
 	rm -f Makefile pkgIndex.tcl-shared pkgIndex.tcl-static nano.syms
 	rm -f pkgIndex.tcl
 	rm -f config.log config.status
 	rm -f nano.tcl.h nano.tcl.h.new.1 nano.tcl.h.new.2
+	rm -rf coverage.dir
 
 mrproper: distclean
 	rm -f @srcdir@/configure @srcdir@/aclocal.m4 @srcdir@/config.guess @srcdir@/config.sub @srcdir@/install-sh
 	rm -f @srcdir@/nano.vers
 	rm -rf @srcdir@/tweetnacl @srcdir@/blake2b

Index: configure.ac
==================================================================
--- configure.ac
+++ configure.ac
@@ -35,10 +35,21 @@
 AC_ARG_ENABLE([debug], AS_HELP_STRING([--enable-debug], [enable debugging parameters]), [
 	if test "$enableval" = "yes"; then
 		tcl_nano_debug='true'
 	fi
 ])
+
+dnl Enable support for a code coverage build
+tcl_nano_coverage='false'
+AC_ARG_ENABLE([coverage], AS_HELP_STRING([--enable-coverage], [enable code coverage build (requires debug)]), [
+	if test "$enableval" = "yes"; then
+		tcl_nano_coverage='true'
+		tcl_nano_debug='true'
+	fi
+])
+
+dnl If we are building a debug release, enable debugging flags
 if test "$tcl_nano_debug" = 'true'; then
 	AC_DEFINE(TCLEXT_TCL_NANO_DEBUG, [1], [Enable debugging build])
 	AX_CHECK_COMPILE_FLAG([-mmpx -fcheck-pointer-bounds], [CFLAGS="$CFLAGS -mmpx -fcheck-pointer-bounds"])
 	AX_CHECK_COMPILE_FLAG([-g3], [CFLAGS="$CFLAGS -g3"])
 	AX_CHECK_COMPILE_FLAG([-ggdb3], [CFLAGS="$CFLAGS -ggdb3"])
@@ -47,10 +58,20 @@
 	AX_CHECK_COMPILE_FLAG([-Wno-unused-value], [CFLAGS="$CFLAGS -Wno-unused-value"])
 	AX_CHECK_COMPILE_FLAG([-Wno-unused-parameter], [CFLAGS="$CFLAGS -Wno-unused-parameter"])
 	AX_CHECK_COMPILE_FLAG([-Wno-deprecated-declarations], [CFLAGS="$CFLAGS -Wno-deprecated-declarations"])
 fi
 AX_CHECK_COMPILE_FLAG([-Wno-sign-compare], [CFLAGS="$CFLAGS -Wno-sign-compare"])
+
+dnl If enabled, do code coverage
+if test "$tcl_nano_coverage" = 'true'; then
+	ENABLE_COVERAGE='true'
+	AC_SUBST(ENABLE_COVERAGE)
+	AX_CHECK_COMPILE_FLAG([-coverage], [
+		CFLAGS="$CFLAGS -coverage"
+		LDFLAGS="$LDFLAGS -coverage"
+	])
+fi
 
 dnl Enable compiler warnings
 AX_CHECK_COMPILE_FLAG([-Wall], [CFLAGS="-Wall $CFLAGS"])
 AX_CHECK_COMPILE_FLAG([-W], [
 	CFLAGS="-W $CFLAGS"