diff --git a/src/xilinx.cpp b/src/xilinx.cpp
index c5ad81d..640190f 100644
--- a/src/xilinx.cpp
+++ b/src/xilinx.cpp
@@ -10,7 +10,7 @@
 #include "part.hpp"
 #include "progressBar.hpp"
 
-Xilinx::Xilinx(Jtag *jtag, std::string filename, bool verbose):
+Xilinx::Xilinx(Jtag *jtag, const std::string &filename, bool verbose):
 	Device(jtag, filename, verbose)
 {
 	if (_filename != ""){
@@ -294,7 +294,7 @@ int Xilinx::spi_wait(uint8_t cmd, uint8_t mask, uint8_t cond,
 			break;
 		}
 		if (verbose) {
-			printf("%x %x %x %d\n", tmp, mask, cond, count);
+			printf("%x %x %x %u\n", tmp, mask, cond, count);
 		}
 	} while ((tmp & mask) != cond);
 	_jtag->go_test_logic_reset();
diff --git a/src/xilinx.hpp b/src/xilinx.hpp
index fd6b88c..a7b56fb 100644
--- a/src/xilinx.hpp
+++ b/src/xilinx.hpp
@@ -10,14 +10,14 @@
 
 class Xilinx: public Device, SPIInterface {
 	public:
-		Xilinx(Jtag *jtag, std::string filename, bool verbose);
+		Xilinx(Jtag *jtag, const std::string &filename, bool verbose);
 		~Xilinx();
 
 		void program(unsigned int offset = 0) override;
 		void program_spi(unsigned int offset = 0);
 		void program_mem(BitParser &bitfile);
-		int idCode();
-		void reset();
+		int idCode() override;
+		void reset() override;
 
 		/* spi interface */
 		int spi_put(uint8_t cmd, uint8_t *tx, uint8_t *rx,