Add --enable-coverage configure option

This configure flag enables lcov [1] coverage generation and is intended
to be used with unit tests (--enable-unit-tests is implied).

A html coverage report can be generated by issuing the following command
in the toplevel build directory:

make coverage

[1] - http://ltp.sourceforge.net/coverage/lcov.php

Based on a patch by Adrian-Ken Rueegsegger.

configure.in

@@ -243,6 +243,7 @@ ARG_ENABL_SET([monolithic],     [build monolithic version of libstrongswan that
 ARG_ENABL_SET([bfd-backtraces], [use binutils libbfd to resolve backtraces for memory leaks and segfaults.])
 ARG_ENABL_SET([unwind-backtraces],[use libunwind to create backtraces for memory leaks and segfaults.])
 ARG_ENABL_SET([unit-tests],     [enable unit tests using the check test framework.])
+ARG_ENABL_SET([coverage],       [enable lcov coverage report generation.])
 ARG_ENABL_SET([tkm],            [enable Trusted Key Manager support.])
 ARG_ENABL_SET([cmd],            [enable the command line IKE client charon-cmd.])
 
@@ -362,6 +363,10 @@ if test x$medcli = xtrue; then
 	mediation=true
 fi
 
+if test x$coverage = xtrue; then
+	unit_tests=true
+fi
+
 # ===========================================
 #  check required libraries and header files
 # ===========================================
@@ -917,6 +922,25 @@ if test x$unit_tests = xtrue; then
 	AC_SUBST(CHECK_LIBS)
 fi
 
+if test x$coverage = xtrue; then
+	AC_PATH_PROG([LCOV], [lcov], [], [$PATH:/bin:/usr/bin:/usr/local/bin])
+	if test x$LCOV = x; then
+		AC_MSG_ERROR([lcov not found])
+	fi
+	AC_PATH_PROG([GENHTML], [genhtml], [], [$PATH:/bin:/usr/bin:/usr/local/bin])
+	if test x$GENHTML = x; then
+		AC_MSG_ERROR([genhtml not found])
+	fi
+
+	COVERAGE_CFLAGS="-fprofile-arcs -ftest-coverage"
+	COVERAGE_LDFLAGS="-fprofile-arcs"
+	AC_SUBST(COVERAGE_CFLAGS)
+	AC_SUBST(COVERAGE_LDFLAGS)
+
+	AC_MSG_NOTICE([coverage enabled, adding "-g -O0" to CFLAGS])
+	CFLAGS="${CFLAGS} -g -O0"
+fi
+
 # ===============================================
 #  collect plugin list for strongSwan components
 # ===============================================
@@ -1241,6 +1265,7 @@ AM_CONDITIONAL(USE_TROUSERS, test x$tss = xtrousers)
 AM_CONDITIONAL(MONOLITHIC, test x$monolithic = xtrue)
 AM_CONDITIONAL(USE_SILENT_RULES, test x$enable_silent_rules = xyes)
 AM_CONDITIONAL(UNITTESTS, test x$unit_tests = xtrue)
+AM_CONDITIONAL(COVERAGE, test x$coverage = xtrue)
 AM_CONDITIONAL(USE_TKM, test x$tkm = xtrue)
 AM_CONDITIONAL(USE_CMD, test x$cmd = xtrue)