diff -up perftest-2.3/configure.ac.cflags perftest-2.3/configure.ac
--- perftest-2.3/configure.ac.cflags	2014-10-17 13:47:35.543196518 -0400
+++ perftest-2.3/configure.ac	2014-10-17 13:47:51.302043917 -0400
@@ -143,7 +143,7 @@ if [test "$CUDA_H_PATH" ]; then
 	LIBS=$LIBS" -lcuda"
 fi
 
-CFLAGS="-g -Wall -D_GNU_SOURCE -O3"
+CFLAGS+=" -g -Wall -D_GNU_SOURCE -O3"
 AC_SUBST([LIBUMAD])
 AC_SUBST([LIBMATH])
 AC_CONFIG_FILES([Makefile])