c++ - sort on a vector of pointers changes data in a copy of the vector? -

i have vector of pointers objects, , @ point, making second vector sub-elements of vector. now, sorting original vector changes elements in second vector (there different elements in after sort).

is expected behaviour? have make_indirect_iterator? there better solution (assuming want keep vector of pointers)?

std::vector<std::shared_ptr<myobj>> vecall; std::vector<std::shared_ptr<myobj>> vecsub;  // fill vecall something...  for(auto obj : vecall) {     if( obj->x >=0 ) {         vecsub.push_back(obj);     } }  // 3 objects in 'vecsub'  std::sort(boost::make_indirect_iterator(vecall.begin()), boost::make_indirect_iterator(vecall.end()), std::greater<myobj>());  // there 3 different objects in 'vecsub' 

yes, it's related make_indirect_iterator. causes object values swapped, instead of reordering pointers.

you instead use normal iterators , perform dereference in comparison step. lambdas make easier:

typedef decltype(vecall.front()) iter; std::sort(vecall.begin(),           vecall.end(),           [](iter a, iter b) { return *a > *b; }); 

version reusable functor (thanks mooingduck suggestion):

struct indirect_greater {     template<typename iter>     bool operator()(iter a, iter b) const { return *a > *b; } };  std::sort(vecall.begin(), vecall.end(), indirect_greater()); 

c++14 adds polymorphic lambdas, let write short lambda [](a, b)(*a > *b) behaves second (functor) solution. no need name iterator type (e.g. decltype).