cmake: disable implicit-fallthrough by default

cmake/OpenCVCompilerOptions.cmake

@@ -138,6 +138,7 @@ if(CMAKE_COMPILER_IS_GNUCXX)
     add_extra_compiler_option(-Wno-delete-non-virtual-dtor)
     add_extra_compiler_option(-Wno-unnamed-type-template-args)
     add_extra_compiler_option(-Wno-comment)
+    add_extra_compiler_option(-Wno-implicit-fallthrough)
   endif()
   add_extra_compiler_option(-fdiagnostics-show-option)
 

modules/core/test/test_math.cpp

@@ -2883,8 +2883,10 @@ TEST(Core_KMeans, compactness)
         }
         EXPECT_NEAR(expected, compactness, expected * 1e-8);
         if (K == N)
+        {
             EXPECT_DOUBLE_EQ(compactness, 0.0);
         }
+    }
 }
 
 TEST(CovariationMatrixVectorOfMat, accuracy)
@@ -3441,8 +3443,10 @@ TEST(Core_SoftFloat, pow32)
         softfloat x32(x.f);
         ASSERT_TRUE(pow(zero, -x32).isInf());
         if(x32 != one)
+        {
             ASSERT_EQ(pow(zero, x32), zero);
         }
+    }
 }
 
 TEST(Core_SoftFloat, pow64)
@@ -3577,8 +3581,10 @@ TEST(Core_SoftFloat, pow64)
 
         ASSERT_TRUE(pow(zero, -x64).isInf());
         if(x64 != one)
+        {
             ASSERT_EQ(pow(zero, x64), zero);
         }
+    }
 }
 
 TEST(Core_SoftFloat, sincos64)

modules/videoio/test/test_video_io.cpp

@@ -178,8 +178,10 @@ public:
         if (ext != "mpg")
         {
             if (count_prop > 0)
+            {
                 EXPECT_EQ(count_gt, count_prop);
             }
+        }
 
         int count_actual = 0;
         while (cap.isOpened())
@@ -193,7 +195,9 @@ public:
             count_actual += 1;
         }
         if (count_prop > 0)
+        {
             EXPECT_NEAR(count_gt, count_actual, 1);
+        }
         else
             std::cout << "Frames counter is not available. Actual frames: " << count_actual << ". SKIP check." << std::endl;
     }