The result of swig running in C++ is different from that in python

void BK::BKTree::recursiveSearchNew(BK::Node *node, std::vector<std::pair<std::string, int> > *r, string w,
                                size_t t) {
size_t curDist = levenshteinDistance(node->word, w);
size_t minDist = curDist - t;
size_t maxDist = curDist + t;

if (curDist <= t) {
    std::pair<string, int> p;
    p = std::make_pair(node->word, curDist);
    r->push_back(p);
}
Node* child = node->leftChild;
if (!child) return;

while (child)
{
    if (inRange(child->distance, minDist, maxDist))
        recursiveSearchNew(child, r, w, t);

    child = child->rightSibling;
}}

This recursive function is compiled by swig and the result vector returns only the last element,but c++ returns normal results。This is the file .i:

%module bk
%include <std_pair.i> 
%include <std_vector.i> 
%include <std_string.i> 
%template() std::pair<std::string,int>; 
%template(PairVector) std::vector<std::pair<std::string,int> >; 
%template(StringVector) std::vector<std::string>;

%{ 
 #include "BKTree.h" 
%} 
 %include "BKTree.h"