diff --git a/3rdparty/ippicv/CMakeLists.txt b/3rdparty/ippicv/CMakeLists.txt
index 43ad806dd7..4ef248f3c0 100644
--- a/3rdparty/ippicv/CMakeLists.txt
+++ b/3rdparty/ippicv/CMakeLists.txt
@@ -24,7 +24,7 @@ if(UNIX)
     set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wno-unused-function -Wno-missing-braces -Wno-missing-field-initializers")
   endif()
   if(CV_CLANG)
-    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wno-self-assign")
+    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wno-self-assign -Wno-strict-prototypes")
   endif()
 endif()
 
diff --git a/modules/core/include/opencv2/core/private.hpp b/modules/core/include/opencv2/core/private.hpp
index 146d37f009..02ac1ba1e3 100644
--- a/modules/core/include/opencv2/core/private.hpp
+++ b/modules/core/include/opencv2/core/private.hpp
@@ -235,6 +235,10 @@ T* allocSingletonNew() { return new(allocSingletonNewBuffer(sizeof(T))) T(); }
 #include "ipp.h"
 #endif
 #ifdef HAVE_IPP_IW
+#  if defined(__OPENCV_BUILD) && defined(__clang__)
+#  pragma clang diagnostic push
+#  pragma clang diagnostic ignored "-Wstrict-prototypes"
+#  endif
 #  if defined(__OPENCV_BUILD) && defined(__GNUC__) && __GNUC__ >= 5
 #  pragma GCC diagnostic push
 #  pragma GCC diagnostic ignored "-Wsuggest-override"
@@ -246,6 +250,9 @@ T* allocSingletonNew() { return new(allocSingletonNewBuffer(sizeof(T))) T(); }
 #  if defined(__OPENCV_BUILD) && defined(__GNUC__) && __GNUC__ >= 5
 #  pragma GCC diagnostic pop
 #  endif
+#  if defined(__OPENCV_BUILD) && defined(__clang__)
+#  pragma clang diagnostic pop
+#  endif
 #endif
 
 #if IPP_VERSION_X100 >= 201700
diff --git a/modules/gapi/misc/python/pyopencv_gapi.hpp b/modules/gapi/misc/python/pyopencv_gapi.hpp
index 49b2ddd1eb..07bacd3665 100644
--- a/modules/gapi/misc/python/pyopencv_gapi.hpp
+++ b/modules/gapi/misc/python/pyopencv_gapi.hpp
@@ -664,7 +664,6 @@ static cv::GRunArgs run_py_kernel(cv::detail::PyObjectHolder kernel,
     cv::GRunArgs outs;
     try
     {
-        int in_idx = 0;
         // NB: Doesn't increase reference counter (false),
         // because PyObject already have ownership.
         // In case exception decrement reference counter.
@@ -697,7 +696,6 @@ static cv::GRunArgs run_py_kernel(cv::detail::PyObjectHolder kernel,
                     util::throw_error(std::logic_error("GFrame isn't supported for custom operation"));
                     break;
             }
-            ++in_idx;
         }
 
         if (ctx.m_state.has_value())
diff --git a/modules/gapi/test/internal/gapi_int_executor_tests.cpp b/modules/gapi/test/internal/gapi_int_executor_tests.cpp
index b8f0e18e0b..79117aebf3 100644
--- a/modules/gapi/test/internal/gapi_int_executor_tests.cpp
+++ b/modules/gapi/test/internal/gapi_int_executor_tests.cpp
@@ -27,7 +27,7 @@ class GMockExecutable final: public cv::gimpl::GIslandExecutable
         m_priv->m_reshape_counter++;
     }
     virtual void handleNewStream() override {  }
-    virtual void run(std::vector<InObj>&&, std::vector<OutObj>&&) { }
+    virtual void run(std::vector<InObj>&&, std::vector<OutObj>&&) override { }
     virtual bool allocatesOutputs() const override
     {
         return true;
diff --git a/modules/gapi/test/streaming/gapi_streaming_tests.cpp b/modules/gapi/test/streaming/gapi_streaming_tests.cpp
index c27ebe3ca2..bdb0ae9cd9 100644
--- a/modules/gapi/test/streaming/gapi_streaming_tests.cpp
+++ b/modules/gapi/test/streaming/gapi_streaming_tests.cpp
@@ -190,7 +190,7 @@ public:
         : cv::gapi::wip::GCaptureSource(pipeline) {
     }
 
-    bool pull(cv::gapi::wip::Data& data) {
+    bool pull(cv::gapi::wip::Data& data) override {
         if (cv::gapi::wip::GCaptureSource::pull(data)) {
             data = cv::MediaFrame::Create<TestMediaBGR>(cv::util::get<cv::Mat>(data));
             return true;
@@ -232,7 +232,7 @@ public:
         : cv::gapi::wip::GCaptureSource(pipeline) {
     }
 
-    bool pull(cv::gapi::wip::Data& data) {
+    bool pull(cv::gapi::wip::Data& data) override {
         if (cv::gapi::wip::GCaptureSource::pull(data)) {
             cv::Mat bgr = cv::util::get<cv::Mat>(data);
             cv::Mat y, uv;
@@ -256,7 +256,7 @@ public:
         : cv::gapi::wip::GCaptureSource(pipeline) {
     }
 
-    bool pull(cv::gapi::wip::Data& data) {
+    bool pull(cv::gapi::wip::Data& data) override {
         if (cv::gapi::wip::GCaptureSource::pull(data)) {
             cv::Mat bgr = cv::util::get<cv::Mat>(data);
             cv::Mat gray;
@@ -319,7 +319,7 @@ public:
         return "InvalidSource sucessfuly failed!";
     }
 
-    bool pull(cv::gapi::wip::Data& d) {
+    bool pull(cv::gapi::wip::Data& d) override {
         ++m_curr_frame_id;
         if (m_curr_frame_id > m_num_frames) {
             return false;
diff --git a/modules/imgproc/test/test_filter.cpp b/modules/imgproc/test/test_filter.cpp
index ad8bac5a47..02d5e232a2 100644
--- a/modules/imgproc/test/test_filter.cpp
+++ b/modules/imgproc/test/test_filter.cpp
@@ -49,10 +49,10 @@ public:
     CV_FilterBaseTest( bool _fp_kernel );
 
 protected:
-    int prepare_test_case( int test_case_idx );
-    int read_params( const cv::FileStorage& fs );
-    void get_test_array_types_and_sizes( int test_case_idx, vector<vector<Size> >& sizes, vector<vector<int> >& types );
-    void get_minmax_bounds( int i, int j, int type, Scalar& low, Scalar& high );
+    int prepare_test_case( int test_case_idx ) CV_OVERRIDE;
+    int read_params( const cv::FileStorage& fs ) CV_OVERRIDE;
+    void get_test_array_types_and_sizes( int test_case_idx, vector<vector<Size> >& sizes, vector<vector<int> >& types ) CV_OVERRIDE;
+    void get_minmax_bounds( int i, int j, int type, Scalar& low, Scalar& high ) CV_OVERRIDE;
     Size aperture_size;
     Point anchor;
     int max_aperture_size;
@@ -689,8 +689,8 @@ public:
     CV_SmoothBaseTest();
 
 protected:
-    void get_test_array_types_and_sizes( int test_case_idx, vector<vector<Size> >& sizes, vector<vector<int> >& types );
-    double get_success_error_level( int test_case_idx, int i, int j );
+    void get_test_array_types_and_sizes( int test_case_idx, vector<vector<Size> >& sizes, vector<vector<int> >& types ) CV_OVERRIDE;
+    double get_success_error_level( int test_case_idx, int i, int j ) CV_OVERRIDE;
     const char* smooth_type;
 
     void dump_test_case(int test_case_idx, std::ostream* out) CV_OVERRIDE
@@ -802,10 +802,10 @@ public:
     CV_GaussianBlurTest();
 
 protected:
-    void prepare_to_validation( int test_case_idx );
-    void run_func();
-    void get_test_array_types_and_sizes( int test_case_idx, vector<vector<Size> >& sizes, vector<vector<int> >& types );
-    double get_success_error_level( int /*test_case_idx*/, int /*i*/, int /*j*/ );
+    void prepare_to_validation( int test_case_idx ) CV_OVERRIDE;
+    void run_func() CV_OVERRIDE;
+    void get_test_array_types_and_sizes( int test_case_idx, vector<vector<Size> >& sizes, vector<vector<int> >& types ) CV_OVERRIDE;
+    double get_success_error_level( int /*test_case_idx*/, int /*i*/, int /*j*/ ) CV_OVERRIDE;
     double sigma;
     int param1, param2;
 
diff --git a/modules/ts/include/opencv2/ts.hpp b/modules/ts/include/opencv2/ts.hpp
index eee0376a0e..86f2d07761 100644
--- a/modules/ts/include/opencv2/ts.hpp
+++ b/modules/ts/include/opencv2/ts.hpp
@@ -116,20 +116,22 @@
 # endif
 #endif
 
-#if defined(__OPENCV_BUILD) && defined(__clang__)
-#pragma clang diagnostic ignored "-Winconsistent-missing-override"
-#endif
 #if defined(__OPENCV_BUILD) && defined(__GNUC__) && __GNUC__ >= 5
 //#pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wsuggest-override"
 #endif
-#if defined(__OPENCV_BUILD) && defined(__APPLE__) && defined(__clang__) && ((__clang_major__*100 + __clang_minor__) >= 1301)
+#if defined(__OPENCV_BUILD) && defined(__clang__) && ((__clang_major__*100 + __clang_minor__) >= 1301)
+#pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wdeprecated-copy"
+#pragma clang diagnostic ignored "-Winconsistent-missing-override"
 #endif
 #include "opencv2/ts/ts_gtest.h"
 #if defined(__OPENCV_BUILD) && defined(__GNUC__) && __GNUC__ >= 5
 //#pragma GCC diagnostic pop
 #endif
+#if defined(__OPENCV_BUILD) && defined(__clang__) && ((__clang_major__*100 + __clang_minor__) >= 1301)
+#pragma clang diagnostic pop
+#endif
 #include "opencv2/ts/ts_ext.hpp"
 
 #ifndef GTEST_USES_SIMPLE_RE
diff --git a/modules/ts/include/opencv2/ts/ts_ext.hpp b/modules/ts/include/opencv2/ts/ts_ext.hpp
index 5c09b569a5..efa4860510 100644
--- a/modules/ts/include/opencv2/ts/ts_ext.hpp
+++ b/modules/ts/include/opencv2/ts/ts_ext.hpp
@@ -49,13 +49,13 @@ bool checkBigDataTests();
 
 
 #undef TEST
-#define TEST_(test_case_name, test_name, parent_class, bodyMethodName, BODY_IMPL) \
+#define TEST_(test_case_name, test_name, parent_class, bodyMethodName, BODY_ATTR, BODY_IMPL) \
     class GTEST_TEST_CLASS_NAME_(test_case_name, test_name) : public parent_class {\
      public:\
       GTEST_TEST_CLASS_NAME_(test_case_name, test_name)() {}\
      private:\
       virtual void TestBody() CV_OVERRIDE;\
-      virtual void bodyMethodName();\
+      virtual void bodyMethodName() BODY_ATTR;\
       static ::testing::TestInfo* const test_info_ GTEST_ATTRIBUTE_UNUSED_;\
       GTEST_DISALLOW_COPY_AND_ASSIGN_(\
           GTEST_TEST_CLASS_NAME_(test_case_name, test_name));\
@@ -74,7 +74,7 @@ bool checkBigDataTests();
     void GTEST_TEST_CLASS_NAME_(test_case_name, test_name)::TestBody() BODY_IMPL( #test_case_name "_" #test_name ) \
     void GTEST_TEST_CLASS_NAME_(test_case_name, test_name)::bodyMethodName()
 
-#define TEST(test_case_name, test_name) TEST_(test_case_name, test_name, ::testing::Test, Body, CV__TEST_BODY_IMPL)
+#define TEST(test_case_name, test_name) TEST_(test_case_name, test_name, ::testing::Test, Body,, CV__TEST_BODY_IMPL)
 
 #define CV__TEST_BIGDATA_BODY_IMPL(name) \
     { \
@@ -96,9 +96,9 @@ bool checkBigDataTests();
 
 // Special type of tests which require / use or validate processing of huge amount of data (>= 2Gb)
 #if defined(_M_X64) || defined(_M_ARM64) || defined(__x86_64__) || defined(__aarch64__)
-#define BIGDATA_TEST(test_case_name, test_name) TEST_(BigData_ ## test_case_name, test_name, ::testing::Test, Body, CV__TEST_BIGDATA_BODY_IMPL)
+#define BIGDATA_TEST(test_case_name, test_name) TEST_(BigData_ ## test_case_name, test_name, ::testing::Test, Body,, CV__TEST_BIGDATA_BODY_IMPL)
 #else
-#define BIGDATA_TEST(test_case_name, test_name) TEST_(BigData_ ## test_case_name, DISABLED_ ## test_name, ::testing::Test, Body, CV__TEST_BIGDATA_BODY_IMPL)
+#define BIGDATA_TEST(test_case_name, test_name) TEST_(BigData_ ## test_case_name, DISABLED_ ## test_name, ::testing::Test, Body,, CV__TEST_BIGDATA_BODY_IMPL)
 #endif
 
 #undef TEST_F
@@ -128,13 +128,13 @@ bool checkBigDataTests();
     void GTEST_TEST_CLASS_NAME_(test_fixture, test_name)::Body()
 
 // Don't use directly
-#define CV__TEST_P(test_case_name, test_name, bodyMethodName, BODY_IMPL/*(name_str)*/) \
+#define CV__TEST_P(test_case_name, test_name, bodyMethodName, BODY_ATTR, BODY_IMPL/*(name_str)*/) \
   class GTEST_TEST_CLASS_NAME_(test_case_name, test_name) \
       : public test_case_name { \
    public: \
     GTEST_TEST_CLASS_NAME_(test_case_name, test_name)() {} \
    private: \
-    virtual void bodyMethodName(); \
+    virtual void bodyMethodName() BODY_ATTR; \
     virtual void TestBody() CV_OVERRIDE; \
     static int AddToRegistry() { \
       ::testing::UnitTest::GetInstance()->parameterized_test_registry(). \
@@ -160,7 +160,7 @@ bool checkBigDataTests();
     void GTEST_TEST_CLASS_NAME_(test_case_name, test_name)::bodyMethodName()
 
 #undef TEST_P
-#define TEST_P(test_case_name, test_name) CV__TEST_P(test_case_name, test_name, Body, CV__TEST_BODY_IMPL)
+#define TEST_P(test_case_name, test_name) CV__TEST_P(test_case_name, test_name, Body,, CV__TEST_BODY_IMPL)
 
 
 #define CV_TEST_EXPECT_EXCEPTION_MESSAGE(statement, msg) \
diff --git a/modules/ts/include/opencv2/ts/ts_perf.hpp b/modules/ts/include/opencv2/ts/ts_perf.hpp
index 5ca22d2b1e..7aa3809f27 100644
--- a/modules/ts/include/opencv2/ts/ts_perf.hpp
+++ b/modules/ts/include/opencv2/ts/ts_perf.hpp
@@ -551,7 +551,7 @@ void PrintTo(const Size& sz, ::std::ostream* os);
 //     EXPECT_TRUE(foo.StatusIsOK());
 //   }
 #define PERF_TEST(test_case_name, test_name)\
-    TEST_(test_case_name, test_name, ::perf::TestBase, PerfTestBody, CV__PERF_TEST_BODY_IMPL)
+    TEST_(test_case_name, test_name, ::perf::TestBase, PerfTestBody, CV_OVERRIDE, CV__PERF_TEST_BODY_IMPL)
 
 // Defines a performance test that uses a test fixture.
 //
@@ -595,7 +595,7 @@ void PrintTo(const Size& sz, ::std::ostream* os);
 //
 // @Note PERF_TEST_P() below violates behavior of original Google Tests - there is no tests instantiation in original TEST_P()
 // This macro is intended for usage with separate INSTANTIATE_TEST_CASE_P macro
-#define PERF_TEST_P_(test_case_name, test_name) CV__TEST_P(test_case_name, test_name, PerfTestBody, CV__PERF_TEST_BODY_IMPL)
+#define PERF_TEST_P_(test_case_name, test_name) CV__TEST_P(test_case_name, test_name, PerfTestBody, CV_OVERRIDE, CV__PERF_TEST_BODY_IMPL)
 
 // Defines a parametrized performance test.
 //
@@ -628,7 +628,7 @@ void PrintTo(const Size& sz, ::std::ostream* os);
      protected:\
       virtual void PerfTestBody();\
     };\
-    CV__TEST_P(fixture##_##name, name, PerfTestBodyDummy, CV__PERF_TEST_BODY_IMPL){} \
+    CV__TEST_P(fixture##_##name, name, PerfTestBodyDummy,, CV__PERF_TEST_BODY_IMPL){} \
     INSTANTIATE_TEST_CASE_P(/*none*/, fixture##_##name, params);\
     void fixture##_##name::PerfTestBody()
 
diff --git a/modules/ts/src/ts_perf.cpp b/modules/ts/src/ts_perf.cpp
index 958a2e300d..39147228b8 100644
--- a/modules/ts/src/ts_perf.cpp
+++ b/modules/ts/src/ts_perf.cpp
@@ -2104,8 +2104,6 @@ struct KeypointComparator
     {
         return cmp(pts_[idx1], pts_[idx2]);
     }
-private:
-    KeypointComparator& operator=(const KeypointComparator&) = delete;
 };
 }//namespace
 
@@ -2119,7 +2117,8 @@ void perf::sort(std::vector<cv::KeyPoint>& pts, cv::InputOutputArray descriptors
     for (int i = 0; i < desc.rows; ++i)
         idxs[i] = i;
 
-    std::sort(idxs.data(), idxs.data() + desc.rows, KeypointComparator(pts));
+    comparators::KeypointGreater cmp;
+    std::sort(idxs.data(), idxs.data() + desc.rows, [&](int lhs, int rhs){ return cmp(pts[lhs], pts[rhs]); });
 
     std::vector<cv::KeyPoint> spts(pts.size());
     cv::Mat sdesc(desc.size(), desc.type());
diff --git a/modules/videoio/src/cap_obsensor/obsensor_uvc_stream_channel.cpp b/modules/videoio/src/cap_obsensor/obsensor_uvc_stream_channel.cpp
index 1bcb6ddf76..35d2a7483f 100644
--- a/modules/videoio/src/cap_obsensor/obsensor_uvc_stream_channel.cpp
+++ b/modules/videoio/src/cap_obsensor/obsensor_uvc_stream_channel.cpp
@@ -198,7 +198,7 @@ DepthFrameUnpacker::DepthFrameUnpacker(){
     outputDataBuf_ = new uint8_t[OUT_DATA_SIZE];
 }
 
-DepthFrameUnpacker::~DepthFrameUnpacker(){
+DepthFrameUnpacker::~DepthFrameUnpacker() {
     delete[] outputDataBuf_;
 }
 
diff --git a/modules/videoio/src/cap_obsensor/obsensor_uvc_stream_channel.hpp b/modules/videoio/src/cap_obsensor/obsensor_uvc_stream_channel.hpp
index 02f4040101..caff38efea 100644
--- a/modules/videoio/src/cap_obsensor/obsensor_uvc_stream_channel.hpp
+++ b/modules/videoio/src/cap_obsensor/obsensor_uvc_stream_channel.hpp
@@ -67,7 +67,7 @@ public:
 class DepthFrameProcessor: public IFrameProcessor {
 public:
     DepthFrameProcessor(const OBExtensionParam& parma);
-    virtual ~DepthFrameProcessor() noexcept;
+    virtual ~DepthFrameProcessor();
     virtual void process(Frame* frame) override;
 
 private:
@@ -78,7 +78,7 @@ private:
 class DepthFrameUnpacker: public IFrameProcessor {
 public:
     DepthFrameUnpacker();
-    virtual ~DepthFrameUnpacker() noexcept;
+    virtual ~DepthFrameUnpacker();
     virtual void process(Frame* frame) override;
 private:
     const uint32_t OUT_DATA_SIZE = 1280*800*2;
diff --git a/samples/cpp/train_svmsgd.cpp b/samples/cpp/train_svmsgd.cpp
index bfd837d507..12e0384081 100644
--- a/samples/cpp/train_svmsgd.cpp
+++ b/samples/cpp/train_svmsgd.cpp
@@ -29,7 +29,7 @@ struct Data
 bool doTrain(const Mat samples, const Mat responses, Mat &weights, float &shift);
 
 //function finds two points for drawing line (wx = 0)
-bool findPointsForLine(const Mat &weights, float shift, Point points[], int width, int height);
+bool findPointsForLine(const Mat &weights, float shift, Point points[2], int width, int height);
 
 // function finds cross point of line (wx = 0) and segment ( (y = HEIGHT, 0 <= x <= WIDTH) or (x = WIDTH, 0 <= y <= HEIGHT) )
 bool findCrossPointWithBorders(const Mat &weights, float shift, const std::pair<Point,Point> &segment, Point &crossPoint);
diff --git a/samples/cpp/warpPerspective_demo.cpp b/samples/cpp/warpPerspective_demo.cpp
index 947abd4359..1a5bb07d87 100644
--- a/samples/cpp/warpPerspective_demo.cpp
+++ b/samples/cpp/warpPerspective_demo.cpp
@@ -157,7 +157,7 @@ static void onMouse(int event, int x, int y, int, void*)
     {
         for (int i = 0; i < 4; ++i)
         {
-            if ((event == EVENT_LBUTTONDOWN) & ((abs(roi_corners[i].x - x) < 10)) & (abs(roi_corners[i].y - y) < 10))
+            if ((event == EVENT_LBUTTONDOWN) && ((abs(roi_corners[i].x - x) < 10)) && (abs(roi_corners[i].y - y) < 10))
             {
                 selected_corner_index = i;
                 dragging = true;