update example for change in function signature

control/examples/wrapper/Makefile

@@ -26,5 +26,5 @@ clean:
 	@echo "Cleaning..."
 	rm -f $(OBJECTS) $(OUT) *.bin gnuplotscript.gp
 
-.cpp.o:
+.c.o:
 	$(COMPILE) -c $< -o $@

control/examples/wrapper/main.c

@@ -1,7 +1,14 @@
 #include "b15f/wrapper/b15f.h"
+#include <stdio.h>
 
 int main() {
-	b15f_t* instance = get_instance();
+	char buf[512];
+	b15f_t* instance = get_instance(buf, sizeof(buf));
+
+	if (instance == NULL) {
+		fprintf(stderr, "%s", buf);
+		return -1;
+	}
 
 	return 0;
 }