eliminate build warnings / fix bug in text module

modules/datasets/CMakeLists.txt

@@ -9,4 +9,7 @@ endif()
 
 ocv_define_module(datasets opencv_core opencv_imgcodecs opencv_ml opencv_flann OPTIONAL opencv_text WRAP python)
 
-ocv_warnings_disable(CMAKE_CXX_FLAGS /wd4267) # flann, Win64
+ocv_warnings_disable(CMAKE_CXX_FLAGS
+    /wd4267                                      # flann, Win64
+    -Wimplicit-fallthrough                       # tinyxml2.cpp
+)

modules/surface_matching/src/hash_murmur64.hpp

@@ -125,16 +125,22 @@ FORCE_INLINE void hashMurmurx64 ( const void * key, const int len, const uint se
   {
   case 7:
     k2 ^= tail[6] << 16;
+    /* fallthrough */
   case 6:
     k2 ^= tail[5] << 8;
+    /* fallthrough */
   case 5:
     k2 ^= tail[4] << 0;
+    /* fallthrough */
   case 4:
     k1 ^= tail[3] << 24;
+    /* fallthrough */
   case 3:
     k1 ^= tail[2] << 16;
+    /* fallthrough */
   case 2:
     k1 ^= tail[1] << 8;
+    /* fallthrough */
   case 1:
     k1 ^= tail[0] << 0;
     bmix32(h1,h2,k1,k2,c1,c2);

modules/text/src/ocr_hmm_decoder.cpp

@@ -935,6 +935,7 @@ Ptr<OCRHMMDecoder::ClassifierCallback> loadOCRHMMClassifier(const String& _filen
             break;
         case OCR_CNN_CLASSIFIER:
             pt = loadOCRHMMClassifierCNN(_filename);
+            break;
         default:
             CV_Error(Error::StsBadArg, "Specified HMM classifier is not supported!");
             break;

modules/ximgproc/src/seeds.cpp

@@ -960,16 +960,16 @@ bool SuperpixelSEEDSImpl::probability(int image_idx, int label1, int label2,
         switch( seeds_prior )
         {
         case 5: p *= p;
-            //no break
+            /* fallthrough */
         case 4: p *= p;
-            //no break
+            /* fallthrough */
         case 3: p *= p;
-            //no break
+            /* fallthrough */
         case 2:
             p *= p;
             P_label1 *= T[seeds_top_level][label2];
             P_label2 *= T[seeds_top_level][label1];
-            //no break
+            /* fallthrough */
         case 1:
             P_label1 *= p;
             break;