View Compilation Error

0_0_20837414_17450.cpp: In instantiation of 'void polar_angle_sort(point_t<T>*, int) [with T = double]':
0_0_20837414_17450.cpp:501:33:   required from 'void graham(point_t<T>*, int, int*, int&) [with T = double]'
0_0_20837414_17450.cpp:532:37:   required from here
0_0_20837414_17450.cpp:497:70: error: 'qsort_r' was not declared in this scope
         qsort_r(pnts+1, n-1, sizeof(point_t<T>), compare_pas<T>, pnts);
                                                                      ^