Remove references to C++ < 17 and older compiler versions.

According to https://github.com/opencv/opencv/wiki/OpenCV-4-to-5-migration#1-build-requirements are not supported: - GCC < 7 - clang < 9 - MSVC < 2017 (19.14)
2026-09-25 04:09:57 +03:00 · 2026-09-24 11:02:15 +02:00
parent aa5546b3e4
commit 32b08d2b9e
46 changed files with 97 additions and 346 deletions
@@ -51,11 +51,7 @@ elseif(CV_CLANG)
    set(OPENCV_LINKER_DEFENSES_FLAGS_COMMON "${OPENCV_LINKER_DEFENSES_FLAGS_COMMON} -z noexecstack -z relro -z now" )
  endif()
 elseif(CV_GCC)
-  if(CMAKE_CXX_COMPILER_VERSION VERSION_LESS "4.9")
-    ocv_add_defense_compiler_flag("-fstack-protector")
-  else()
  ocv_add_defense_compiler_flag("-fstack-protector-strong")
-  endif()

  # These flags is added by general options: -Wformat -Wformat-security
  if(NOT CMAKE_CXX_FLAGS MATCHES "-Wformat" OR NOT CMAKE_CXX_FLAGS MATCHES "format-security")
@@ -296,7 +296,6 @@ if(X86 OR X86_64)
    ocv_update(CPU_SSSE3_FLAGS_ON "-mssse3")
    ocv_update(CPU_SSE2_FLAGS_ON "-msse2")
    ocv_update(CPU_SSE_FLAGS_ON "-msse")
-    if(NOT (CV_GCC AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS "5.0"))  # GCC >= 5.0
    ocv_update(CPU_AVX_512F_FLAGS_ON "-mavx512f")
    ocv_update(CPU_AVX_512CD_FLAGS_ON "-mavx512cd")
    ocv_update(CPU_AVX512_KNL_EXTRA_FLAGS_ON "-mavx512er -mavx512pf")
@@ -310,9 +309,6 @@ if(X86 OR X86_64)
    ocv_update(CPU_AVX_512VBMI2_FLAGS_ON "-mavx512vbmi2")
    ocv_update(CPU_AVX_512BITALG_FLAGS_ON "-mavx512bitalg")
    ocv_update(CPU_AVX_512VPOPCNTDQ_FLAGS_ON "-mavx512vpopcntdq")
-    else()
-      ocv_update(CPU_AVX_512F_SUPPORTED OFF)
-    endif()
  elseif(MSVC)
    ocv_update(CPU_AVX2_FLAGS_ON "/arch:AVX2")
    ocv_update(CPU_AVX_FLAGS_ON "/arch:AVX")
@@ -149,21 +149,17 @@ if(CV_GCC OR CV_CLANG OR CV_ICX)
  add_extra_compiler_option(-Wundef)
  add_extra_compiler_option(-Winit-self)
  add_extra_compiler_option(-Wpointer-arith)
-  if(NOT (CV_GCC AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS "5.0"))
-    add_extra_compiler_option(-Wshadow)  # old GCC emits warnings for variables + methods combination
-  endif()
+  add_extra_compiler_option(-Wshadow)
  add_extra_compiler_option(-Wsign-promo)
  add_extra_compiler_option(-Wuninitialized)
-  if(CV_GCC AND (CMAKE_CXX_COMPILER_VERSION VERSION_GREATER 6.0) AND (CMAKE_CXX_COMPILER_VERSION VERSION_LESS 7.0 OR ARM))
+  if(CV_GCC AND ARM)
    add_extra_compiler_option(-Wno-psabi)
  endif()
-  if(HAVE_CXX11)
  if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU" AND NOT ENABLE_PRECOMPILED_HEADERS)
    add_extra_compiler_option(-Wsuggest-override)
  elseif(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
    add_extra_compiler_option(-Winconsistent-missing-override)
  endif()
-  endif()

  if(ENABLE_NOISY_WARNINGS)
    add_extra_compiler_option(-Wcast-align)
@@ -174,16 +170,13 @@ if(CV_GCC OR CV_CLANG OR CV_ICX)
    add_extra_compiler_option(-Wno-comment)
    if(NOT OPENCV_SKIP_IMPLICIT_FALLTHROUGH
        AND NOT " ${CMAKE_CXX_FLAGS} ${OPENCV_EXTRA_FLAGS} ${OPENCV_EXTRA_CXX_FLAGS}" MATCHES "implicit-fallthrough"
-        AND (CV_GCC AND NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 7.0.0)
+        AND (CV_GCC OR CV_CLANG)
    )
      add_extra_compiler_option(-Wimplicit-fallthrough=3)
    endif()
    if(CV_GCC AND CMAKE_CXX_COMPILER_VERSION VERSION_GREATER 7.0)
      add_extra_compiler_option(-Wno-strict-overflow) # Issue appears when compiling surf.cpp from opencv_contrib/modules/xfeatures2d
    endif()
-    if(CV_GCC AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 5.0)
-      add_extra_compiler_option(-Wno-missing-field-initializers)  # GCC 4.x emits warnings about {}, fixed in GCC 5+
-    endif()
    if(CV_CLANG AND NOT CMAKE_CXX_COMPILER_ID STREQUAL "AppleClang" AND NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 10.0)
      add_extra_compiler_option(-Wno-deprecated-enum-enum-conversion)
      add_extra_compiler_option(-Wno-deprecated-anon-enum-enum-conversion)
@@ -266,9 +259,6 @@ if(CV_GCC OR CV_CLANG OR CV_ICX)
  endif()

  if(ENABLE_INSTRUMENTATION)
-    if(NOT HAVE_CXX11)
-      message(WARNING "ENABLE_INSTRUMENTATION requires C++11 support")
-    endif()
    set(WITH_VTK OFF) # There are issues with VTK 6.0
  endif()

@@ -314,9 +304,7 @@ if(MSVC)

  # Remove unreferenced functions: function level linking
  set(OPENCV_EXTRA_FLAGS "${OPENCV_EXTRA_FLAGS} /Gy")
-  if(NOT MSVC_VERSION LESS 1400)
  set(OPENCV_EXTRA_FLAGS "${OPENCV_EXTRA_FLAGS} /bigobj")
-  endif()

  if(OPENCV_WARNINGS_ARE_ERRORS)
    set(OPENCV_EXTRA_FLAGS "${OPENCV_EXTRA_FLAGS} /WX")
@@ -327,7 +315,7 @@ if(MSVC)
    set(OPENCV_EXTRA_EXE_LINKER_FLAGS_RELEASE "${OPENCV_EXTRA_EXE_LINKER_FLAGS_RELEASE} /LTCG")
  endif()

-  if(NOT MSVC_VERSION LESS 1800 AND NOT CMAKE_GENERATOR MATCHES "Visual Studio")
+  if(NOT CMAKE_GENERATOR MATCHES "Visual Studio")
    set(OPENCV_EXTRA_C_FLAGS "${OPENCV_EXTRA_C_FLAGS} /FS")
    set(OPENCV_EXTRA_CXX_FLAGS "${OPENCV_EXTRA_CXX_FLAGS} /FS")
  endif()
@@ -405,7 +405,7 @@ macro(ocv_nvcc_flags)
  endif()

  # disabled because of multiple warnings during building nvcc auto generated files
-  if(CV_GCC AND CMAKE_CXX_COMPILER_VERSION VERSION_GREATER "4.6.0")
+  if(CV_GCC)
    ocv_warnings_disable(CMAKE_CXX_FLAGS -Wunused-but-set-variable)
  endif()
 endmacro()
@@ -203,24 +203,11 @@ if(NOT OPENCV_SKIP_CMAKE_CXX_STANDARD)
  ocv_update(CMAKE_CXX_STANDARD 17)
  ocv_update(CMAKE_CXX_STANDARD_REQUIRED TRUE)
  ocv_update(CMAKE_CXX_EXTENSIONS OFF) # use -std=c++17 instead of -std=gnu++17
-  if("cxx_std_11" IN_LIST CMAKE_CXX_COMPILE_FEATURES)
-    set(HAVE_CXX11 ON)
-  endif()
-  if("cxx_std_17" IN_LIST CMAKE_CXX_COMPILE_FEATURES)
-    set(HAVE_CXX17 ON)
-  endif()
 endif()

-if(NOT HAVE_CXX11)
-  message(WARNING "OpenCV 5.x requires C++11 support, but it was not detected. Your compilation may fail.")
-endif()
-if(NOT HAVE_CXX17)
-  message(WARNING "OpenCV 5.x requires C++17 support, but it was not detected. Your compilation may fail.")
-endif()
-
-# Debian 10 - GCC 8.3.0
-if(CV_GCC AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 8)
-  message(WARNING "OpenCV requires GCC >= 8.x (detected ${CMAKE_CXX_COMPILER_VERSION}). Your compilation may fail.")
+# Debian 9 - GCC 7.3.0
+if(CV_GCC AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 7)
+  message(WARNING "OpenCV requires GCC >= 7.x (detected ${CMAKE_CXX_COMPILER_VERSION}). Your compilation may fail.")
 endif()

 # Debian 10 - Clang 7.0
@@ -236,12 +223,12 @@ endif()
 # TODO: check other known compilers versions

 set(__OPENCV_ENABLE_ATOMIC_LONG_LONG OFF)
-if(HAVE_CXX11 AND (X86 OR X86_64))
+if(X86 OR X86_64)
  set(__OPENCV_ENABLE_ATOMIC_LONG_LONG ON)
 endif()
 option(OPENCV_ENABLE_ATOMIC_LONG_LONG "Enable C++ compiler support for atomic<long long>" ${__OPENCV_ENABLE_ATOMIC_LONG_LONG})

-if((HAVE_CXX11 AND OPENCV_ENABLE_ATOMIC_LONG_LONG
+if((OPENCV_ENABLE_ATOMIC_LONG_LONG
        AND NOT MSVC
        AND NOT (X86 OR X86_64)
    AND NOT OPENCV_SKIP_LIBATOMIC_COMPILER_CHECK)
@@ -260,6 +247,6 @@ if((HAVE_CXX11 AND OPENCV_ENABLE_ATOMIC_LONG_LONG
  else()
    set(HAVE_ATOMIC_LONG_LONG ON)
  endif()
-else(HAVE_CXX11 AND OPENCV_ENABLE_ATOMIC_LONG_LONG)
+else()
  set(HAVE_ATOMIC_LONG_LONG ${OPENCV_ENABLE_ATOMIC_LONG_LONG})
 endif()
@@ -149,7 +149,7 @@ IF(OPENEXR_FOUND)
  if(NOT OPENEXR_VERSION)
    SET(OPENEXR_VERSION "Unknown")
  else()
-    if(HAVE_CXX17 AND OPENEXR_VERSION VERSION_LESS "2.3.0")
+    if(OPENEXR_VERSION VERSION_LESS "2.3.0")
      message(STATUS "  OpenEXR(ver ${OPENEXR_VERSION}) doesn't support C++17 and higher. Updating OpenEXR 2.3.0+ is required.")
      SET(OPENEXR_FOUND FALSE)
    endif()
@@ -78,15 +78,6 @@ endif()
 #   Details: https://protobuf.dev/news/2022-08-03/
 # And if std::text_view is in abseil-cpp requests C++17 and later.

-if(HAVE_PROTOBUF)
-  if(NOT (Protobuf_VERSION VERSION_LESS 22))
-    if((CMAKE_CXX_STANDARD EQUAL 98) OR (CMAKE_CXX_STANDARD LESS 17))
-      message(STATUS "CMAKE_CXX_STANDARD=${CMAKE_CXX_STANDARD} is too old to support protobuf(${Protobuf_VERSION}) and/or abseil-cpp. Use C++17 or later. Turning HAVE_PROTOBUF off")
-      set(HAVE_PROTOBUF FALSE)
-    endif()
-  endif()
-endif()
-
 if(HAVE_PROTOBUF AND PROTOBUF_UPDATE_FILES AND NOT COMMAND PROTOBUF_GENERATE_CPP)
  message(FATAL_ERROR "Can't configure protobuf dependency (BUILD_PROTOBUF=${BUILD_PROTOBUF} PROTOBUF_UPDATE_FILES=${PROTOBUF_UPDATE_FILES})")
 endif()
@@ -2,7 +2,7 @@ if(NOT DEFINED MIN_VER_CMAKE)
  set(MIN_VER_CMAKE 3.13) # Debian 10
  # set(MIN_VER_CMAKE 3.10) # Visual Studio 2017 15.7
 endif()
-set(MIN_VER_CUDA 6.5)
+set(MIN_VER_CUDA 9.0) # CUDA 9.0 is the minimum version supporting stable C++11 compilation for device code
 set(MIN_VER_CUDNN 7.5)
 set(MIN_VER_CUDNNJIT 9.0)
 set(MIN_VER_PYTHON3 3.2)
@@ -14,9 +14,7 @@

 IF(CV_GCC)

-    IF(NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS "4.2.0")
    SET(PCHSupport_FOUND TRUE)
-    ENDIF()

    SET(_PCH_include_prefix "-I")
    SET(_PCH_isystem_prefix "-isystem")
@@ -65,7 +63,7 @@ MACRO(_PCH_GET_COMPILE_FLAGS _out_compile_flags)
        ocv_is_opencv_directory(__result ${item})
        if(__result)
          LIST(APPEND ${_out_compile_flags} "${_PCH_include_prefix}\"${item}\"")
-        elseif(CV_GCC AND NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS "6.0" AND
+        elseif(CV_GCC AND
               item MATCHES "/usr/include$")
          # workaround for GCC 6.x bug
        else()
@@ -78,7 +76,7 @@ MACRO(_PCH_GET_COMPILE_FLAGS _out_compile_flags)
        ocv_is_opencv_directory(__result ${item})
        if(__result)
          LIST(APPEND ${_out_compile_flags} "${_PCH_include_prefix}\"${item}\"")
-        elseif(CV_GCC AND NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS "6.0" AND
+        elseif(CV_GCC AND
               item MATCHES "/usr/include$")
          # workaround for GCC 6.x bug
        else()
@@ -70,7 +70,6 @@ function(ocv_create_plugin module default_name dependency_target dependency_targ

  target_link_libraries(${OPENCV_PLUGIN_NAME} PRIVATE ${dependency_target})
  set_target_properties(${OPENCV_PLUGIN_NAME} PROPERTIES
-    CXX_STANDARD 11
    CXX_VISIBILITY_PRESET hidden
  )

@@ -305,7 +305,7 @@ function(ocv_include_directories)
    ocv_is_opencv_directory(__is_opencv_dir "${dir}")
    if(__is_opencv_dir)
      list(APPEND __add_before "${dir}")
-    elseif(((CV_GCC AND NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS "6.0") OR CV_CLANG) AND
+    elseif((CV_GCC OR CV_CLANG) AND
           dir MATCHES "/usr/include$")
      # workaround for GCC 6.x bug
    else()
@@ -359,7 +359,7 @@ function(ocv_target_include_directories target)
    if("${dir}" STREQUAL "SYSTEM")
      set(__var_name __system_params)
    else()
-      if(CV_GCC AND NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS "6.0" AND
+      if(CV_GCC AND
          dir MATCHES "/usr/include$")
         # workaround for GCC 6.x bug
      else()
@@ -139,7 +139,7 @@ option(OPENCV_ENABLE_ALLOCATOR_STATS "Enable Allocator metrics" ON)

 if(NOT OPENCV_ENABLE_ALLOCATOR_STATS)
  add_definitions(-DOPENCV_DISABLE_ALLOCATOR_STATS=1)
-elseif(HAVE_CXX11 OR DEFINED OPENCV_ALLOCATOR_STATS_COUNTER_TYPE)
+else()
  if(NOT DEFINED OPENCV_ALLOCATOR_STATS_COUNTER_TYPE)
    if(HAVE_ATOMIC_LONG_LONG AND OPENCV_ENABLE_ATOMIC_LONG_LONG)
      if(MINGW)
@@ -50,7 +50,7 @@
 #if defined(__OPENCV_BUILD) && defined(__clang__)
 #pragma clang diagnostic ignored "-Winconsistent-missing-override"
 #endif
-#if defined(__OPENCV_BUILD) && defined(__GNUC__) && __GNUC__ >= 5
+#if defined(__OPENCV_BUILD) && defined(__GNUC__)
 #pragma GCC diagnostic ignored "-Wsuggest-override"
 #endif

@@ -90,11 +90,9 @@ namespace cv { namespace debug_build_guard { } using namespace debug_build_guard

 #ifdef CV_Func
 // keep current value (through OpenCV port file)
-#elif defined __GNUC__ || (defined (__cpluscplus) && (__cpluscplus >= 201103))
+#elif defined __GNUC__ || defined __clang__ || defined __cplusplus
 #define CV_Func __func__
-#elif defined __clang__ && (__clang_minor__ * 100 + __clang_major__ >= 305)
-#define CV_Func __func__
-#elif defined(__STDC_VERSION__) && (__STDC_VERSION >= 199901)
+#elif defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L)
 #define CV_Func __func__
 #elif defined _MSC_VER
 #define CV_Func __FUNCTION__
@@ -114,36 +112,12 @@ namespace cv { namespace debug_build_guard { } using namespace debug_build_guard
 #define CVAUX_CONCAT_EXP(a, b) a##b
 #define CVAUX_CONCAT(a, b) CVAUX_CONCAT_EXP(a,b)

-#if defined(__clang__)
-#  ifndef __has_extension
-#    define __has_extension __has_feature /* compatibility, for older versions of clang */
-#  endif
-#  if __has_extension(cxx_static_assert)
+#if defined(__cplusplus) || (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 202311L)
 #  define CV_StaticAssert(condition, reason) static_assert((condition), reason " " #condition)
-#  elif __has_extension(c_static_assert)
+#elif defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L
 #  define CV_StaticAssert(condition, reason) _Static_assert((condition), reason " " #condition)
-#  endif
-#elif defined(__GNUC__)
-#  if (defined(__GXX_EXPERIMENTAL_CXX0X__) || __cplusplus >= 201103L)
-#    define CV_StaticAssert(condition, reason)    static_assert((condition), reason " " #condition)
-#  endif
-#elif defined(_MSC_VER)
-#  if _MSC_VER >= 1600 /* MSVC 10 */
-#    define CV_StaticAssert(condition, reason)    static_assert((condition), reason " " #condition)
-#  endif
-#endif
-#ifndef CV_StaticAssert
-#  if !defined(__clang__) && defined(__GNUC__) && (__GNUC__*100 + __GNUC_MINOR__ > 302)
-#    define CV_StaticAssert(condition, reason) ({ extern int __attribute__((error("CV_StaticAssert: " reason " " #condition))) CV_StaticAssert(); ((condition) ? 0 : CV_StaticAssert()); })
-#  else
-namespace cv {
-     template <bool x> struct CV_StaticAssert_failed;
-     template <> struct CV_StaticAssert_failed<true> { enum { val = 1 }; };
-     template<int x> struct CV_StaticAssert_test {};
-}
-#    define CV_StaticAssert(condition, reason)\
-       typedef cv::CV_StaticAssert_test< sizeof(cv::CV_StaticAssert_failed< static_cast<bool>(condition) >) > CVAUX_CONCAT(CV_StaticAssert_failed_at_, __LINE__)
-#  endif
+#else
+#  define CV_StaticAssert(condition, reason)
 #endif

 // Suppress warning "-Wdeprecated-declarations" / C4996
@@ -220,7 +194,7 @@ namespace cv {
 #endif

 #ifndef CV_ALWAYS_INLINE
-#if defined(__GNUC__) && (__GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 1))
+#if defined(__GNUC__)
 #define CV_ALWAYS_INLINE inline __attribute__((always_inline))
 #elif defined(_MSC_VER)
 #define CV_ALWAYS_INLINE __forceinline
@@ -437,7 +411,7 @@ Cv64suf;
 #ifndef CV_EXPORTS
 # if (defined _WIN32 || defined WINCE || defined __CYGWIN__) && defined(CVAPI_EXPORTS)
 #   define CV_EXPORTS __declspec(dllexport)
-# elif defined __GNUC__ && __GNUC__ >= 4 && (defined(CVAPI_EXPORTS) || defined(__APPLE__))
+# elif defined __GNUC__ && (defined(CVAPI_EXPORTS) || defined(__APPLE__))
 #   define CV_EXPORTS __attribute__ ((visibility ("default")))
 # endif
 #endif
@@ -729,21 +703,10 @@ __CV_ENUM_FLAGS_BITWISE_XOR_EQ   (EnumType, EnumType)

 #ifdef CV_XADD
  // allow to use user-defined macro
-#elif defined __GNUC__ || defined __clang__
-#  if defined __clang__ && __clang_major__ >= 3 && !defined __EMSCRIPTEN__ && !defined __INTEL_COMPILER
-#    ifdef __ATOMIC_ACQ_REL
+#elif defined __clang__ && !defined __EMSCRIPTEN__ && !defined __INTEL_COMPILER
 #  define CV_XADD(addr, delta) __c11_atomic_fetch_add((_Atomic(int)*)(addr), delta, __ATOMIC_ACQ_REL)
-#    else
-#      define CV_XADD(addr, delta) __atomic_fetch_add((_Atomic(int)*)(addr), delta, 4)
-#    endif
-#  else
-#    if defined __ATOMIC_ACQ_REL && !defined __clang__
-       // version for gcc >= 4.7
+#elif defined __GNUC__ || defined __clang__
 #  define CV_XADD(addr, delta) (int)__atomic_fetch_add((unsigned*)(addr), (unsigned)(delta), __ATOMIC_ACQ_REL)
-#    else
-#      define CV_XADD(addr, delta) (int)__sync_fetch_and_add((unsigned*)(addr), (unsigned)(delta))
-#    endif
-#  endif
 #elif defined _MSC_VER && !defined RC_INVOKED
 #  include <intrin.h>
 #  define CV_XADD(addr, delta) (int)_InterlockedExchangeAdd((long volatile*)addr, delta)
@@ -785,20 +748,9 @@ __CV_ENUM_FLAGS_BITWISE_XOR_EQ   (EnumType, EnumType)
 #    else
 #       define CV_NODISCARD_STD [[nodiscard]]
 #    endif
-#  elif __cplusplus >= 201703L
+#  else
 //   available when compiler is C++17 compliant
 #    define CV_NODISCARD_STD [[nodiscard]]
-#  elif defined(__INTEL_COMPILER)
-     // see above, available when C++17 is enabled
-#  elif defined(_MSC_VER) && _MSC_VER >= 1911 && _MSVC_LANG >= 201703L
-//   available with VS2017 v15.3+ with /std:c++17 or higher; works on functions and classes
-#    define CV_NODISCARD_STD [[nodiscard]]
-#  elif defined(__GNUC__) && (((__GNUC__ * 100) + __GNUC_MINOR__) >= 700) && (__cplusplus >= 201103L)
-//   available with GCC 7.0+; works on functions, works or silently fails on classes
-#    define CV_NODISCARD_STD [[nodiscard]]
-#  elif defined(__GNUC__) && (((__GNUC__ * 100) + __GNUC_MINOR__) >= 408) && (__cplusplus >= 201103L)
-//   available with GCC 4.8+ but it usually does nothing and can fail noisily -- therefore not used
-//   define CV_NODISCARD_STD [[gnu::warn_unused_result]]
 #  endif
 #endif
 #ifndef CV_NODISCARD_STD
@@ -810,21 +762,11 @@ __CV_ENUM_FLAGS_BITWISE_XOR_EQ   (EnumType, EnumType)
 *                                    C++ 11                                              *
 \****************************************************************************************/
 #ifdef __cplusplus
-// MSVC was stuck at __cplusplus == 199711L for a long time, even where it supports C++11,
-// so check _MSC_VER instead. See:
-// <https://devblogs.microsoft.com/cppblog/msvc-now-correctly-reports-__cplusplus>
-#  if defined(_MSC_VER)
-#    if _MSC_VER < 1800
-#      error "OpenCV 4.x+ requires enabled C++11 support"
-#    endif
-#  elif __cplusplus < 201103L
-#    error "OpenCV 4.x+ requires enabled C++11 support"
+#  if __cplusplus < 201103L && !(defined(_MSC_VER) && _MSVC_LANG >= 201103L)
+#    error "OpenCV 5.x+ requires enabled C++11 support"
 #  endif
 #endif

-#ifndef CV_CXX11
-#  define CV_CXX11 1
-#endif

 #ifndef CV_OVERRIDE
 #  define CV_OVERRIDE override
@@ -51,7 +51,7 @@

 #include "opencv2/core.hpp"

-#if defined _MSC_VER && _MSC_VER >= 1200
+#if defined _MSC_VER
 #ifndef NOMINMAX
 #define NOMINMAX // fix https://github.com/opencv/opencv/issues/17548
 #endif
@@ -64,7 +64,7 @@
 namespace {
 inline unsigned int trailingZeros32(unsigned int value) {
 #if defined(_MSC_VER)
-#if (_MSC_VER < 1700) || defined(_M_ARM) || defined(_M_ARM64) || defined(_M_ARM64EC)
+#if defined(_M_ARM) || defined(_M_ARM64) || defined(_M_ARM64EC)
    unsigned long index = 0;
    _BitScanForward(&index, value);
    return (unsigned int)index;
@@ -1464,12 +1464,7 @@ inline v_float32x16 v_abs(const v_float32x16& x)
 inline v_float64x8 v_abs(const v_float64x8& x)
 {
 #ifdef _mm512_abs_pd
-    #if defined __GNUC__ && (__GNUC__ < 7 || (__GNUC__ == 7 && __GNUC_MINOR__ <= 3) || (__GNUC__ == 8 && __GNUC_MINOR__ <= 2))
-        // Workaround for https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87476
-        return v_float64x8(_mm512_abs_pd(_mm512_castpd_ps(x.val)));
-    #else
    return v_float64x8(_mm512_abs_pd(x.val));
-    #endif
 #else
    return v_float64x8(_mm512_castsi512_pd(_mm512_and_si512(_mm512_castpd_si512(x.val),
                       _v512_set_epu64(0x7FFFFFFFFFFFFFFF, 0x7FFFFFFFFFFFFFFF, 0x7FFFFFFFFFFFFFFF, 0x7FFFFFFFFFFFFFFF,
@@ -167,23 +167,13 @@ public:
    //! default constructor
    Point_();
    Point_(_Tp _x, _Tp _y);
-#if (defined(__GNUC__) && __GNUC__ < 5) && !defined(__clang__)  // GCC 4.x bug. Details: https://github.com/opencv/opencv/pull/20837
-    Point_(const Point_& pt);
-    Point_(Point_&& pt) CV_NOEXCEPT = default;
-#elif OPENCV_ABI_COMPATIBILITY < 500
    Point_(const Point_& pt) = default;
    Point_(Point_&& pt) CV_NOEXCEPT = default;
-#endif
    Point_(const Size_<_Tp>& sz);
    Point_(const Vec<_Tp, 2>& v);

-#if (defined(__GNUC__) && __GNUC__ < 5) && !defined(__clang__)  // GCC 4.x bug. Details: https://github.com/opencv/opencv/pull/20837
-    Point_& operator = (const Point_& pt);
-    Point_& operator = (Point_&& pt) CV_NOEXCEPT = default;
-#elif OPENCV_ABI_COMPATIBILITY < 500
    Point_& operator = (const Point_& pt) = default;
    Point_& operator = (Point_&& pt) CV_NOEXCEPT = default;
-#endif
    //! conversion to another data type
    template<typename _Tp2> operator Point_<_Tp2>() const;

@@ -1204,12 +1194,6 @@ template<typename _Tp> inline
 Point_<_Tp>::Point_(_Tp _x, _Tp _y)
    : x(_x), y(_y) {}

-#if (defined(__GNUC__) && __GNUC__ < 5) && !defined(__clang__)  // GCC 4.x bug. Details: https://github.com/opencv/opencv/pull/20837
-template<typename _Tp> inline
-Point_<_Tp>::Point_(const Point_& pt)
-    : x(pt.x), y(pt.y) {}
-#endif
-
 template<typename _Tp> inline
 Point_<_Tp>::Point_(const Size_<_Tp>& sz)
    : x(sz.width), y(sz.height) {}
@@ -1218,15 +1202,6 @@ template<typename _Tp> inline
 Point_<_Tp>::Point_(const Vec<_Tp,2>& v)
    : x(v[0]), y(v[1]) {}

-#if (defined(__GNUC__) && __GNUC__ < 5) && !defined(__clang__)  // GCC 4.x bug. Details: https://github.com/opencv/opencv/pull/20837
-template<typename _Tp> inline
-Point_<_Tp>& Point_<_Tp>::operator = (const Point_& pt)
-{
-    x = pt.x; y = pt.y;
-    return *this;
-}
-#endif
-
 template<typename _Tp> template<typename _Tp2> inline
 Point_<_Tp>::operator Point_<_Tp2>() const
 {
@@ -344,33 +344,8 @@ VSX_IMPL_1RG(vec_udword2, vec_float4,  xvcvspuxds, vec_ctulo)
 VSX_FINLINE(rt) fnm(const rg& a) { return __builtin_convertvector(a, rt); }

 #ifndef vec_permi
-#if __clang_major__ < 5
-// implement vec_permi in a dirty way
-#   define VSX_IMPL_CLANG_4_PERMI(Tvec)                                                 \
-    VSX_FINLINE(Tvec) vec_permi(const Tvec& a, const Tvec& b, unsigned const char c)    \
-    {                                                                                   \
-        switch (c)                                                                      \
-        {                                                                               \
-        case 0:                                                                         \
-            return vec_mergeh(a, b);                                                    \
-        case 1:                                                                         \
-            return vec_mergel(vec_mergeh(a, a), b);                                     \
-        case 2:                                                                         \
-            return vec_mergeh(vec_mergel(a, a), b);                                     \
-        default:                                                                        \
-            return vec_mergel(a, b);                                                    \
-        }                                                                               \
-    }
-    VSX_IMPL_CLANG_4_PERMI(vec_udword2)
-    VSX_IMPL_CLANG_4_PERMI(vec_dword2)
-    VSX_IMPL_CLANG_4_PERMI(vec_double2)
-
-// vec_xxsldwi is missing in clang 4
-#   define vec_xxsldwi(a, b, c) vec_sld(a, b, (c) * 4)
-#else
 // vec_xxpermdi is missing little-endian supports in clang 4 just like gcc4
 #   define vec_permi(a, b, c) vec_xxpermdi(b, a, (3 ^ (((c) & 1) << 1 | (c) >> 1)))
-#endif // __clang_major__ < 5
 #endif

 // shift left double by word immediate
@@ -429,25 +404,19 @@ VSX_IMPL_CONVERT(vec_double2, vec_dword2,  vec_ctd)
 VSX_IMPL_CONVERT(vec_double2, vec_udword2, vec_ctd)

 // converts word and doubleword to single-precision
-#if __clang_major__ > 4
-#   undef vec_ctf
-#endif
+#undef vec_ctf
 VSX_IMPL_CONVERT(vec_float4, vec_int4,    vec_ctf)
 VSX_IMPL_CONVERT(vec_float4, vec_uint4,   vec_ctf)
 VSX_REDIRECT_1RG(vec_float4, vec_dword2,  vec_ctfo, __builtin_vsx_xvcvsxdsp)
 VSX_REDIRECT_1RG(vec_float4, vec_udword2, vec_ctfo, __builtin_vsx_xvcvuxdsp)

 // converts single and double precision to signed word
-#if __clang_major__ > 4
-#   undef vec_cts
-#endif
+#undef vec_cts
 VSX_REDIRECT_1RG(vec_int4,  vec_double2, vec_ctso, __builtin_vsx_xvcvdpsxws)
 VSX_IMPL_CONVERT(vec_int4,  vec_float4,  vec_cts)

 // converts single and double precision to unsigned word
-#if __clang_major__ > 4
-#   undef vec_ctu
-#endif
+#undef vec_ctu
 VSX_REDIRECT_1RG(vec_uint4, vec_double2, vec_ctuo, __builtin_vsx_xvcvdpuxws)
 VSX_IMPL_CONVERT(vec_uint4, vec_float4,  vec_ctu)

@@ -510,7 +479,6 @@ VSX_IMPL_CONV_EVEN_2_4(vec_uint4,  vec_double2, vec_ctu, vec_ctuo)
 * changing behavior of conversion intrinsics for gcc has effect on Eigen
 * so we redefine old behavior again only on gcc, clang
 */
-#if !defined(__clang__) || __clang_major__ > 4
    // ignoring second arg since Eigen only truncates toward zero
 #   define VSX_IMPL_CONV_2VARIANT(rt, rg, fnm, fn2)     \
    VSX_FINLINE(rt) fnm(const rg& a, int only_truncate) \
@@ -526,7 +494,6 @@ VSX_IMPL_CONV_EVEN_2_4(vec_uint4,  vec_double2, vec_ctu, vec_ctuo)
    // define vec_cts for converting double precision to signed doubleword
    // which isn't compatible with xlc but its okay since Eigen only uses it for gcc
    VSX_IMPL_CONV_2VARIANT(vec_dword2, vec_double2, vec_cts, vec_ctsl)
-#endif // Eigen

 #endif // Common GCC, CLANG compatibility

@@ -48,12 +48,6 @@
 namespace cv
 {

-// On Win64 optimized versions of DFT and DCT fail the tests (fixed in VS2010)
-#if defined _MSC_VER && !defined CV_ICC && defined _M_X64 && _MSC_VER < 1600
-# pragma optimize("", off)
-# pragma warning(disable: 4748)
-#endif
-
 #if IPP_VERSION_X100 >= 710
 #define USE_IPP_DFT 1
 #else
@@ -58,10 +58,6 @@
 #  include "opencv2/core/eigen.hpp"
 #endif

-#if defined _M_IX86 && defined _MSC_VER && _MSC_VER < 1700
-#pragma float_control(precise, on)
-#endif
-
 namespace cv
 {

@@ -88,7 +88,7 @@
    #define HAVE_GCD
 #endif

-#if defined _MSC_VER && _MSC_VER >= 1600
+#if defined _MSC_VER
    #define HAVE_CONCURRENCY
 #endif

@@ -128,8 +128,6 @@
 #elif defined HAVE_GCD
    #include <dispatch/dispatch.h>
    #include <pthread.h>
-#elif defined WINRT && _MSC_VER < 1900
-    #include <ppltasks.h>
 #elif defined HAVE_CONCURRENCY
    #include <ppl.h>
 #elif defined HAVE_PTHREADS_PF
@@ -519,7 +519,7 @@ CoreTLSData& getCoreTlsData();
 #if defined(BUILD_SHARED_LIBS)
 #if defined _WIN32 || defined WINCE
 #define CL_RUNTIME_EXPORT __declspec(dllexport)
-#elif defined __GNUC__ && __GNUC__ >= 4
+#elif defined __GNUC__
 #define CL_RUNTIME_EXPORT __attribute__ ((visibility ("default")))
 #else
 #define CL_RUNTIME_EXPORT
@@ -869,7 +869,6 @@ TEST(Core_Allocation, alignedAllocation)
 }


-#if !(defined(__GNUC__) && __GNUC__ < 5)  // GCC 4.8 emits: 'is_trivially_copyable' is not a member of 'std'
 TEST(Core_Types, trivially_copyable)
 {
    EXPECT_TRUE(std::is_trivially_copyable<cv::Complexd>::value);
@@ -889,7 +888,6 @@ TEST(Core_Types, trivially_copyable_extra)
    EXPECT_TRUE(std::is_trivially_copyable<cv::TermCriteria>::value);
    EXPECT_TRUE(std::is_trivially_copyable<cv::Moments>::value);
 }
-#endif

 template <typename T> class Rect_Test : public testing::Test {};

@@ -100,11 +100,6 @@ CV_OperationsTest::~CV_OperationsTest() {}
 #define CHECK_DIFF(a, b) checkDiff(a, b, "(" #a ")  !=  (" #b ")  at l." STR(__LINE__))
 #define CHECK_DIFF_FLT(a, b) checkDiffF(a, b, "(" #a ")  !=(eps)  (" #b ")  at l." STR(__LINE__))

-#if defined _MSC_VER && _MSC_VER < 1400
-#define MSVC_OLD 1
-#else
-#define MSVC_OLD 0
-#endif

 template<typename _Tp> void CV_OperationsTest::TestType(Size sz, _Tp value)
 {
@@ -295,9 +290,7 @@ bool CV_OperationsTest::TestMat()
        CHECK_DIFF(4.0 * (maskMat1 | maskMat1), maskMat4);
        CHECK_DIFF((maskMat4 | maskMat4)/4.0, maskMat1);

-#if !MSVC_OLD
        CHECK_DIFF(2.0 * (maskMat1 * 2.0) , maskMat4);
-#endif
        CHECK_DIFF((maskMat4 / 2.0) / 2.0 , maskMat1);
        CHECK_DIFF(-(maskMat4 - maskMat5) , maskMat1);
        CHECK_DIFF(-((maskMat4 - maskMat5) * 1.0), maskMat1);
@@ -363,7 +356,6 @@ bool CV_OperationsTest::TestMat()

        m = maskMat1.clone(); m+=(maskMat1 * 3.0 + 1.0); CHECK_DIFF(m, maskMat5);
        m = maskMat5.clone(); m-=(maskMat1 * 3.0 + 1.0); CHECK_DIFF(m, maskMat1);
-#if !MSVC_OLD
        m = mi.clone(); m+=(3.0 * mi * mt + d1); CHECK_DIFF_FLT(m, mi + d1 * 4);
        m = mi.clone(); m-=(3.0 * mi * mt + d1); CHECK_DIFF_FLT(m, mi - d1 * 4);
        m = mi.clone(); m*=(mt * 1.0); CHECK_DIFF_FLT(m, d1);
@@ -420,7 +412,6 @@ bool CV_OperationsTest::TestMat()
        CHECK_DIFF_FLT(mt.inv() * mt, d1);

        CHECK_DIFF_FLT(mt.inv() * (2*mt - mt), d1);
-#endif
    }
    catch (const test_excep& e)
    {
@@ -93,10 +93,6 @@ endif()
 if(HAVE_CUDA)
  ocv_warnings_disable(CMAKE_CXX_FLAGS -Wundef)
 endif()
-if(NOT HAVE_CXX11)
-  ocv_warnings_disable(CMAKE_CXX_FLAGS -Wno-undef)  # LANG_CXX11 from protobuf files
-endif()
-
 if(APPLE_FRAMEWORK)
  ocv_warnings_disable(CMAKE_CXX_FLAGS -Wshorten-64-to-32)
 endif()
@@ -55,15 +55,7 @@ enum class NearestMode {
    ROUND_PREFER_FLOOR
 };

-#if __cplusplus < 201703L
-template<typename T>
-static T clamp(T d, T min, T max)
-{
-    return std::min(std::max(d, min), max);
-}
-#else
-#define clamp std::clamp
-#endif
+using std::clamp;

 static inline NearestMode parseNearestMode(const String& s)
 {
@@ -15,15 +15,7 @@ namespace cv
 namespace dnn
 {

-#if __cplusplus < 201703L
-template<typename T>
-static T clamp(T d, T min, T max)
-{
-    return std::min(std::max(d, min), max);
-}
-#else
-#define clamp std::clamp
-#endif
+using std::clamp;

 static MatShape inferTransformLayoutShape(const MatShape& inpshape_,
                                          DataLayout outlayout,
@@ -9,12 +9,12 @@
 #define __OPENCV_DNN_ONNX_SIMPLIFIER_HPP__
 #ifdef HAVE_PROTOBUF

-#if defined(__GNUC__) && __GNUC__ >= 5
+#if defined(__GNUC__)
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wsuggest-override"
 #endif
 #include "opencv-onnx.pb.h"
-#if defined(__GNUC__) && __GNUC__ >= 5
+#if defined(__GNUC__)
 #pragma GCC diagnostic pop
 #endif

@@ -31,17 +31,12 @@
 #include <algorithm>


-#if defined _MSC_VER && _MSC_VER < 1910/*MSVS 2017*/
-#pragma warning(push)
-#pragma warning(disable: 4503)  // decorated name length exceeded, name was truncated
-#endif
-
-#if defined(__GNUC__) && __GNUC__ >= 5
+#if defined(__GNUC__)
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wsuggest-override"
 #endif
 #include "opencv-onnx.pb.h"
-#if defined(__GNUC__) && __GNUC__ >= 5
+#if defined(__GNUC__)
 #pragma GCC diagnostic pop
 #endif

@@ -28,17 +28,12 @@
 #include <string>
 #include <unordered_map>

-#if defined _MSC_VER && _MSC_VER < 1910/*MSVS 2017*/
-#pragma warning(push)
-#pragma warning(disable: 4503)  // decorated name length exceeded, name was truncated
-#endif
-
-#if defined(__GNUC__) && __GNUC__ >= 5
+#if defined(__GNUC__)
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wsuggest-override"
 #endif
 #include "opencv-onnx.pb.h"
-#if defined(__GNUC__) && __GNUC__ >= 5
+#if defined(__GNUC__)
 #pragma GCC diagnostic pop
 #endif

@@ -34,7 +34,7 @@
 #define INF_ENGINE_VER_MAJOR_LE(ver) (((INF_ENGINE_RELEASE) / 10000) <= ((ver) / 10000))
 #define INF_ENGINE_VER_MAJOR_EQ(ver) (((INF_ENGINE_RELEASE) / 10000) == ((ver) / 10000))

-#if defined(__GNUC__) && __GNUC__ >= 5
+#if defined(__GNUC__)
 //#pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wsuggest-override"
 #endif
@@ -43,7 +43,7 @@
 #include <openvino/pass/serialize.hpp>
 #include <openvino/pass/convert_fp32_to_fp16.hpp>

-#if defined(__GNUC__) && __GNUC__ >= 5
+#if defined(__GNUC__)
 //#pragma GCC diagnostic pop
 #endif

@@ -13,7 +13,7 @@ Declaration of various functions which are related to Tensorflow models reading.
 #define __OPENCV_DNN_TF_IO_HPP__
 #ifdef HAVE_PROTOBUF

-#if defined(__GNUC__) && __GNUC__ >= 5
+#if defined(__GNUC__)
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wsuggest-override"
 #endif
@@ -22,7 +22,7 @@ Declaration of various functions which are related to Tensorflow models reading.
 #include <google/protobuf/message.h>
 #include <google/protobuf/text_format.h>
 #include <google/protobuf/io/zero_copy_stream_impl.h>
-#if defined(__GNUC__) && __GNUC__ >= 5
+#if defined(__GNUC__)
 #pragma GCC diagnostic pop
 #endif

@@ -14,10 +14,8 @@ namespace cv

 struct Random
 {
-    static const uint64 default_seed = 0xffffffff;
-    #if __cplusplus < 201103L
    typedef uint64 seed_type;
-    #endif
+    static const uint64 default_seed = 0xffffffff;

    RNG rng;

@@ -406,7 +406,7 @@ int GenericIndex<Distance>::radiusSearch(const std::vector<ElementType>& query,

    FLANN_DISTANCE_CHECK

-    return nnIndex->radiusSearch(m_query,m_indices,m_dists,radius,searchParams);
+    return nnIndex->radiusSearch(m_query,m_indices,m_dists,static_cast<float>(radius),searchParams);
 }

 template <typename Distance>
@@ -426,7 +426,7 @@ int GenericIndex<Distance>::radiusSearch(const Mat& query, Mat& indices, Mat& di

    FLANN_DISTANCE_CHECK

-    return nnIndex->radiusSearch(m_query,m_indices,m_dists,radius,searchParams);
+    return nnIndex->radiusSearch(m_query,m_indices,m_dists,static_cast<float>(radius),searchParams);
 }

 /**
@@ -502,8 +502,8 @@ public:
        ::cvflann::Matrix<int> m_indices(&indices[0], 1, indices.size());
        ::cvflann::Matrix<DistanceType> m_dists(&dists[0], 1, dists.size());

-        if (nnIndex_L1) return nnIndex_L1->radiusSearch(m_query,m_indices,m_dists,radius,searchParams);
-        if (nnIndex_L2) return nnIndex_L2->radiusSearch(m_query,m_indices,m_dists,radius,searchParams);
+        if (nnIndex_L1) return nnIndex_L1->radiusSearch(m_query,m_indices,m_dists,static_cast<float>(radius),searchParams);
+        if (nnIndex_L2) return nnIndex_L2->radiusSearch(m_query,m_indices,m_dists,static_cast<float>(radius),searchParams);
    }

    CV_DEPRECATED int radiusSearch(const Mat& query, Mat& indices, Mat& dists, DistanceType radius, const ::cvflann::SearchParams& searchParams)
@@ -520,8 +520,8 @@ public:
        CV_Assert(dists.isContinuous());
        ::cvflann::Matrix<DistanceType> m_dists((DistanceType*)dists.ptr<DistanceType>(0), dists.rows, dists.cols);

-        if (nnIndex_L1) return nnIndex_L1->radiusSearch(m_query,m_indices,m_dists,radius,searchParams);
-        if (nnIndex_L2) return nnIndex_L2->radiusSearch(m_query,m_indices,m_dists,radius,searchParams);
+        if (nnIndex_L1) return nnIndex_L1->radiusSearch(m_query,m_indices,m_dists,static_cast<float>(radius),searchParams);
+        if (nnIndex_L2) return nnIndex_L2->radiusSearch(m_query,m_indices,m_dists,static_cast<float>(radius),searchParams);
    }

    CV_DEPRECATED void save(String filename)
@@ -36,6 +36,7 @@
 #include <algorithm>
 #include <map>
 #include <cstring>
+#include <random>

 #include "nn_index.h"
 #include "dynamic_bitset.h"
@@ -143,7 +144,8 @@ public:
 #ifndef OPENCV_FLANN_USE_STD_RAND
            cv::randShuffle(vind_);
 #else
-            std::random_shuffle(vind_.begin(), vind_.end());
+            std::mt19937 std_rng(12345);
+            std::shuffle(vind_.begin(), vind_.end(), std_rng);
 #endif

            tree_roots_[i] = divideTree(vind_.data(), int(size_) );
@@ -38,6 +38,7 @@
 //! @cond IGNORED

 #include <algorithm>
+#include <random>
 #include <cmath>
 #include <iostream>
 #include <iomanip>
@@ -362,7 +363,8 @@ inline LshTable<unsigned char>::LshTable(unsigned int feature_size, unsigned int
 #ifndef OPENCV_FLANN_USE_STD_RAND
    cv::randShuffle(indices);
 #else
-    std::random_shuffle(indices.begin(), indices.end());
+    std::mt19937 std_rng(12345);
+    std::shuffle(indices.begin(), indices.end(), std_rng);
 #endif

    // Generate a random set of order of subsignature_size_ bits
@@ -36,6 +36,7 @@
 #include <algorithm>
 #include <cstdlib>
 #include <vector>
+#include <random>

 namespace cvflann
 {
@@ -127,7 +128,8 @@ public:
 #ifndef OPENCV_FLANN_USE_STD_RAND
        cv::randShuffle(vals_);
 #else
-        std::random_shuffle(vals_.begin(), vals_.end());
+        std::mt19937 std_rng(12345);
+        std::shuffle(vals_.begin(), vals_.end(), std_rng);
 #endif

        counter_ = 0;
@@ -4,10 +4,6 @@

 #include <cmath>
 #include <complex>
-#if defined (_MSC_VER) && (_MSC_VER <= 1700)
-static inline double cbrt(double x) { return (double)cv::cubeRoot((float)x); };
-#endif
-
 namespace {
 void polishQuarticRoots(const double *coeffs, double *roots, int nb_roots) {
    const int iterations = 2;
@@ -317,10 +317,6 @@ struct MomentsInTile_SIMD<ushort, int, int64>
 #endif // CV_SIMD || CV_SIMD_SCALABLE

 template<typename T, typename WT, typename MT>
-#if defined __GNUC__ && __GNUC__ == 4 && __GNUC_MINOR__ >= 5 && __GNUC_MINOR__ < 9
-// Workaround for http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60196
-__attribute__((optimize("no-tree-vectorize")))
-#endif
 static void momentsInTile( const Mat& img, double* moments )
 {
    Size size = img.size();
@@ -47,7 +47,7 @@
 #include <opencv2/core/utils/configuration.private.hpp>
 #include <opencv2/core/utils/logger.hpp>

-#if defined _MSC_VER && _MSC_VER >= 1200
+#if defined _MSC_VER
 #  pragma warning( disable: 4100 4244 4267 )
 #endif

@@ -110,7 +110,7 @@
 #include "grfmt_png.hpp"
 #include <opencv2/core/utils/logger.hpp>

-#if defined _MSC_VER && _MSC_VER >= 1200
+#if defined _MSC_VER
    // interaction between '_setjmp' and C++ object destruction is non-portable
    #pragma warning( disable: 4611 )
    #pragma warning( disable: 4244 )
@@ -44,14 +44,6 @@

 using namespace cv;

-// std::isnan is a part of C++11 and it is not supported in MSVS2010/2012
-#if defined _MSC_VER && _MSC_VER < 1800 /* MSVC 2013 */
-#include <float.h>
-namespace std {
-template <typename T> bool isnan(T value) { return _isnan(value) != 0; }
-}
-#endif
-
 template <typename T> struct pixelInfo_
 {
    static const int channels = 1;
@@ -116,7 +116,7 @@
 # endif
 #endif

-#if defined(__OPENCV_BUILD) && defined(__GNUC__) && __GNUC__ >= 5
+#if defined(__OPENCV_BUILD) && defined(__GNUC__)
 //#pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wsuggest-override"
 #endif
@@ -126,7 +126,7 @@
 #pragma clang diagnostic ignored "-Winconsistent-missing-override"
 #endif
 #include "opencv2/ts/ts_gtest.h"
-#if defined(__OPENCV_BUILD) && defined(__GNUC__) && __GNUC__ >= 5
+#if defined(__OPENCV_BUILD) && defined(__GNUC__)
 //#pragma GCC diagnostic pop
 #endif
 #if defined(__OPENCV_BUILD) && defined(__clang__) && ((__clang_major__*100 + __clang_minor__) >= 1301)
@@ -60,9 +60,6 @@ using namespace cv;

 #define CALC_FFMPEG_VERSION(a,b,c) ( a<<16 | b<<8 | c )

-#if defined _MSC_VER && _MSC_VER >= 1200
-#pragma warning( disable: 4244 4510 4610 )
-#endif

 #ifdef __GNUC__
 #  pragma GCC diagnostic ignored "-Wdeprecated-declarations"
@@ -162,12 +159,6 @@ inline static AVRational av_make_q(int num, int den)
 }
 #endif

-// GCC 4.x compilation bug. Details: https://github.com/opencv/opencv/issues/20292
-#if (defined(__GNUC__) && __GNUC__ < 5) && !defined(__clang__)
-#undef USE_AV_HW_CODECS
-#define USE_AV_HW_CODECS 0
-#endif
-
 //#define USE_AV_HW_CODECS 0
 #ifndef USE_AV_HW_CODECS
 #if LIBAVUTIL_VERSION_MAJOR >= 56 // FFMPEG 4.0+
@@ -178,9 +169,7 @@ inline static AVRational av_make_q(int num, int den)
 #endif
 #endif

-#if defined _MSC_VER && _MSC_VER >= 1200
-#pragma warning( default: 4244 4510 4610 )
-#endif
+

 #ifdef NDEBUG
 #define CV_WARN(message)
@@ -190,13 +179,6 @@ inline static AVRational av_make_q(int num, int den)

 #if defined _WIN32
    #include <windows.h>
-    #if defined _MSC_VER && _MSC_VER < 1900
-    struct timespec
-    {
-        time_t tv_sec;
-        long   tv_nsec;
-    };
-  #endif
 #elif defined __linux__ || defined __APPLE__ || defined __HAIKU__
    #include <unistd.h>
    #include <stdio.h>
@@ -14,7 +14,7 @@ extern "C"
 #   define OPENCV_FFMPEG_API
 #elif defined _WIN32
 #   define OPENCV_FFMPEG_API __declspec(dllexport)
-#elif defined __GNUC__ && __GNUC__ >= 4
+#elif defined __GNUC__
 #   define OPENCV_FFMPEG_API __attribute__ ((visibility ("default")))
 #else
 #   define OPENCV_FFMPEG_API