fix build warnings

modules/dnn/src/dnn.cpp

@@ -62,7 +62,9 @@ CV__DNN_EXPERIMENTAL_NS_BEGIN
 // this option is useful to run valgrind memory errors detection
 static bool DNN_DISABLE_MEMORY_OPTIMIZATIONS = utils::getConfigurationParameterBool("OPENCV_DNN_DISABLE_MEMORY_OPTIMIZATIONS", false);
 
+#ifdef HAVE_OPENCL
 static bool DNN_OPENCL_ALLOW_ALL_DEVICES = utils::getConfigurationParameterBool("OPENCV_DNN_OPENCL_ALLOW_ALL_DEVICES", false);
+#endif
 
 using std::vector;
 using std::map;

modules/stitching/src/blenders.cpp

@@ -661,7 +661,7 @@ void MultiBandBlender::blend(InputOutputArray dst, InputOutputArray dst_mask)
         }
 
         // Set destination Mats to 0 so new image can be blended
-        for (size_t i = 0; i < num_bands_ + 1; ++i)
+        for (size_t i = 0; i < (size_t)(num_bands_ + 1); ++i)
         {
             gpu_dst_band_weights_[i].setTo(0);
             gpu_dst_pyr_laplace_[i].setTo(Scalar::all(0));