C++: "Error: Pointer being freed was not allocated" when handling large lists -

i trying process data in std::vector made of 2d points; basically, need check whether or not points are, directly or indirectly through point, linked relationship don't think needs detailed here.

in order process data properly, copied data vector , used lists faster handling.

i wrote following 2d vector class:

class float2d { public:     float x, y;      float2d(): x(0), y(0) {}     float2d(int a, int b): x(a), y(b) {}      bool checkstuffwith(float2d &u); // math }; 

the code used process data looks this:

bool checkstuffinvector(vector<float2d> const &data) {      if (data.size() < 2) return true;      // copy data in list, thinned out progressively     list<float2d> data_copy(data.begin(), data.end());      // points used checkstuff remaining points in data_copy     list<float2d> processed_data;      // choose arbitrarily last element compare others     processed_data.push_back(data_copy.back());     data_copy.pop_back();      list<float2d>::iterator it1;     list<float2d>::iterator it2 = data_copy.begin();      while (!processed_data.empty()) {         it1 = processed_data.begin();         if (it1->checkstuffwith(*it2)) {             // *it2 fulfills relationship             // remove point data_copy             // , put in processed_data             processed_data.push_back(*it2);             data_copy.erase(it2);         } else {             // move on next point process             it2++;         }         if (it2 == data_copy.end() && !data_copy.empty()) {             // checked necessary stuff *it1             // no need keep in processed_data             processed_data.pop_front();             it2 = data_copy.begin();         } else if (data_copy.empty()) {             break;         }     }      return data_copy.empty(); } 

this runs fine relatively low values data.size(), need work bigger values. when vector's size 1,000,000, following runtime error:

malloc: *** error object 0x7fac0e341240: pointer being freed not allocated

i can't figure out comes from. overlooked something, can't see is; figured outsider's might :)

i want point out such problem handled using tree structure, because of size of problem, might cause tree's height big (thus, risk of stack overflow?) , fact want runs fast, thought i'd better off doing way.

thanks in advance!

when data_copy.erase(it2) invalidate iterator it2, dereference iterator in next iteration of while loop. ub.

i suggest resolve replacing erase line this

it2 = data_copy.erase(it2) 

which replace it2 iterator valid iterator pointing next element or data_copy.end() if list empty.