Merge remote-tracking branch 'upstream/3.4' into merge-3.4

diff --cc modules/core/include/opencv2/core/mat.hpp
Simple merge

diff --cc modules/core/include/opencv2/core/mat.inl.hpp
Simple merge

diff --cc modules/core/src/precomp.hpp
Simple merge

diff --cc modules/core/test/test_mat.cpp
index 17bcd55,18906f8..b43ab20
--- 1/modules/core/test/test_mat.cpp
--- 2/modules/core/test/test_mat.cpp
+++ b/modules/core/test/test_mat.cpp
@@@ -1766,4 -1774,28 +1766,26 @@@ TEST(Mat_, template_based_ptr
      ASSERT_FLOAT_EQ(66.0f, *(mat.ptr<float>(idx)));
  }
  
 -#endif
 -
+ 
+ BIGDATA_TEST(Mat, push_back_regression_4158)  // memory usage: ~10.6 Gb
+ {
+     Mat result;
+ 
+     Mat tail(100, 500000, CV_32FC2, Scalar(1, 2));
+ 
+     tail.copyTo(result);
+     for (int i = 1; i < 15; i++)
+     {
+         result.push_back(tail);
+         std::cout << "i = " << i << "  result = " << result.size() << "   used = " << (uint64)result.total()*result.elemSize()*(1.0 / (1 << 20)) << " Mb"
+             << "   allocated=" << (uint64)(result.datalimit - result.datastart)*(1.0 / (1 << 20)) << " Mb" << std::endl;
+     }
+     for (int i = 0; i < 15; i++)
+     {
+         Rect roi(0, tail.rows * i, tail.cols, tail.rows);
+         int nz = countNonZero(result(roi).reshape(1) == 2);
+         EXPECT_EQ(tail.total(), (size_t)nz) << "i=" << i;
+     }
+ }
+ 
  }} // namespace

diff --cc modules/stitching/src/blenders.cpp
Simple merge