build: eliminate GCC8 warnings

Author: alalek

modules/bgsegm/src/bgfg_gsoc.cpp

@@ -237,7 +237,8 @@ class BackgroundModel {
                     if (p.y >= size.height)
                         p.y = size.height - 1;
 
-                    memcpy(&samples[i * stride + j * nSamples], &bm.samples[p.y * stride + p.x * nSamples], sizeof(BackgroundSampleType) * nSamples);
+                    for (int k = 0; k < nSamples; k++)
+                        samples[i * stride + j * nSamples + k] = bm.samples[p.y * stride + p.x * nSamples + k];
                 }
     }
 

modules/bioinspired/samples/OpenEXRimages_HDR_Retina_toneMapping.cpp

@@ -294,7 +294,7 @@ int main(int argc, char* argv[])
 			 */
 			cv::waitKey(10);
 		}
-	}catch(cv::Exception e)
+	} catch(const cv::Exception& e)
 	{
 		std::cerr<<"Error using Retina : "<<e.what()<<std::endl;
 	}

modules/rgbd/src/linemod.cpp

@@ -994,8 +994,8 @@ static void spread(const Mat& src, Mat& dst, int T)
     int height = src.rows - r;
     for (int c = 0; c < T; ++c)
     {
-      orUnaligned8u(&src.at<unsigned char>(r, c), static_cast<const int>(src.step1()), dst.ptr(),
-                    static_cast<const int>(dst.step1()), src.cols - c, height);
+      orUnaligned8u(&src.at<unsigned char>(r, c), static_cast<int>(src.step1()), dst.ptr(),
+                    static_cast<int>(dst.step1()), src.cols - c, height);
     }
   }
 }

modules/sfm/src/libmv_light/CMakeLists.txt

@@ -4,5 +4,8 @@ include(CMake/Installation.cmake)
 set(BUILD_SHARED_LIBS OFF) # Force static libs for 3rdparty dependencies
 
 ocv_warnings_disable(CMAKE_CXX_FLAGS -Winconsistent-missing-override -Wsuggest-override)
+if(CV_GCC AND CMAKE_CXX_COMPILER_VERSION VERSION_GREATER 8.0)
+  ocv_warnings_disable(CMAKE_CXX_FLAGS -Wclass-memaccess)
+endif()
 
 add_subdirectory(libmv)