Merge pull request #23276 from vovka643:flann_corrections

Fixed potential memory leak in flann

Issue #22426

### Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [x] The PR is proposed to the proper branch
- [x] There is a reference to the original bug report and related work
- [x] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [x] The feature is well documented and sample code can be built with the project CMake

modules/flann/include/opencv2/flann/flann_base.hpp

@@ -45,6 +45,21 @@
 
 namespace cvflann
 {
+class FILEScopeGuard {
+
+public:
+    explicit FILEScopeGuard(FILE* file) {
+        file_ = file;
+    };
+
+    ~FILEScopeGuard() {
+        fclose(file_);
+    };
+
+private:
+    FILE* file_;
+};
+
 
 /**
  * Sets the log level used for all flann functions
@@ -69,7 +84,6 @@ struct SavedIndexParams : public IndexParams
     }
 };
 
-
 template<typename Distance>
 NNIndex<Distance>* load_saved_index(const Matrix<typename Distance::ElementType>& dataset, const cv::String& filename, Distance distance)
 {
@@ -79,13 +93,13 @@ NNIndex<Distance>* load_saved_index(const Matrix<typename Distance::ElementType>
     if (fin == NULL) {
         return NULL;
     }
+    FILEScopeGuard fscgd(fin);
+
     IndexHeader header = load_header(fin);
     if (header.data_type != Datatype<ElementType>::type()) {
-        fclose(fin);
         FLANN_THROW(cv::Error::StsError, "Datatype of saved index is different than of the one to be created.");
     }
     if ((size_t(header.rows) != dataset.rows)||(size_t(header.cols) != dataset.cols)) {
-        fclose(fin);
         FLANN_THROW(cv::Error::StsError, "The index saved belongs to a different dataset");
     }
 
@@ -93,7 +107,6 @@ NNIndex<Distance>* load_saved_index(const Matrix<typename Distance::ElementType>
     params["algorithm"] = header.index_type;
     NNIndex<Distance>* nnIndex = create_index_by_type<Distance>(dataset, params, distance);
     nnIndex->loadIndex(fin);
-    fclose(fin);
 
     return nnIndex;
 }
@@ -107,7 +120,7 @@ public:
     typedef typename Distance::ResultType DistanceType;
 
     Index(const Matrix<ElementType>& features, const IndexParams& params, Distance distance = Distance() )
-        : index_params_(params)
+        :index_params_(params)
     {
         flann_algorithm_t index_type = get_param<flann_algorithm_t>(params,"algorithm");
         loaded_ = false;

modules/flann/src/miniflann.cpp

@@ -767,11 +767,15 @@ bool Index::load(InputArray _data, const String& filename)
     Mat data = _data.getMat();
     bool ok = true;
     release();
+
     FILE* fin = fopen(filename.c_str(), "rb");
-    if (fin == NULL)
+    if (fin == NULL) {
         return false;
+    }
+    FILEScopeGuard fscgd(fin);
 
     ::cvflann::IndexHeader header = ::cvflann::load_header(fin);
+
     algo = header.index_type;
     featureType = header.data_type == FLANN_UINT8 ? CV_8U :
                   header.data_type == FLANN_INT8 ? CV_8S :
@@ -786,7 +790,6 @@ bool Index::load(InputArray _data, const String& filename)
     {
         fprintf(stderr, "Reading FLANN index error: the saved data size (%d, %d) or type (%d) is different from the passed one (%d, %d), %d\n",
                 (int)header.rows, (int)header.cols, featureType, data.rows, data.cols, data.type());
-        fclose(fin);
         return false;
     }
 
@@ -799,7 +802,6 @@ bool Index::load(InputArray _data, const String& filename)
           (distType != FLANN_DIST_HAMMING && featureType == CV_32F)) )
     {
         fprintf(stderr, "Reading FLANN index error: unsupported feature type %d for the index type %d\n", featureType, algo);
-        fclose(fin);
         return false;
     }
 
@@ -839,8 +841,6 @@ bool Index::load(InputArray _data, const String& filename)
         ok = false;
     }
 
-    if( fin )
-        fclose(fin);
     return ok;
 }