Test for expl function presence.

CMakeLists.txt

@@ -883,6 +883,7 @@ CHECK_FUNCTION_EXISTS(wait4 HAVE_WAIT4)
 CHECK_FUNCTION_EXISTS(waitpid HAVE_WAITPID)
 CHECK_FUNCTION_EXISTS(flock HAVE_FLOCK)
 CHECK_FUNCTION_EXISTS(tanhl HAVE_TANHL)
+CHECK_FUNCTION_EXISTS(expl HAVE_EXPL)
 CHECK_FUNCTION_EXISTS(sendfile HAVE_SENDFILE)
 CHECK_FUNCTION_EXISTS(mkstemp HAVE_MKSTEMP)
 CHECK_FUNCTION_EXISTS(setitimer HAVE_SETITIMER)

config.h.in

@@ -144,6 +144,8 @@
 
 #cmakedefine HAVE_TANHL          1
 
+#cmakedefine HAVE_EXPL           1
+
 #cmakedefine HAVE_SA_SIGINFO     1
 
 #cmakedefine DEBUG_MODE          1

src/classifiers/bayes.c

@@ -121,7 +121,11 @@ inv_chi_square (gdouble value, gint freedom_deg)
 
 	value /= 2.;
 	errno = 0;
+#ifdef HAVE_EXPL
 	prob = expl (-value);
+#else
+	prob = exp (-value);
+#endif
 	if (errno == ERANGE) {
 		msg_err ("exp overflow");
 		return 0;