c++ - Segmentation fault while iterating through and erasing some elements from std::map? -


i using several std::map type data containers following:

    std::map<int, std::vector< cv::point > > mapgoodcontours;     std::map<int, ellipseproperties> ellipsepropertiesmap;     std::map<int, float> m_markerradiusmap;     std::map<int,cv::point2f> markers;//this part of class

i iterate through these containers , erase elements after elements meet condition shown in following code.

    auto radiusmapcounter = m_markerradiusmap.begin();     auto markercounter = frames.markers.begin();     auto goodcontourscounter = mapgoodcontours.begin();      if(m_markerradiusmap.size()==ellipsepropertiesmap.size() && frames.markers.size()==ellipsepropertiesmap.size()             && mapgoodcontours.size()==ellipsepropertiesmap.size())     {         for(auto ellipsepropertycounter = ellipsepropertiesmap.begin(); ellipsepropertycounter != ellipsepropertiesmap.end(); ellipsepropertycounter++)         {              float upperlimit = (float)m_upperfactor*(float)ellipsepropertycounter->second.radius;             float lowerlimit = (float)m_lowerfactor*(float)ellipsepropertycounter->second.radius;             if(ellipsepropertycounter->second.mindistancefromotherellipse>upperlimit                         || ellipsepropertycounter->second.mindistancefromotherellipse<lowerlimit)             {                  ellipsepropertiesmap.erase(ellipsepropertycounter);                  m_markerradiusmap.erase(radiusmapcounter);                  frames.markers.erase(markercounter);                  mapgoodcontours.erase(goodcontourscounter);             }             else             {                  smallcontours.push_back(goodcontourscounter->second);             }              radiusmapcounter++;             markercounter++;             goodcontourscounter++;         }     }

i baffled find have segmentation faults shown in image. enter image description here fault points line code radiusmapcounter++;

what doing wrong?

you cannot increment iterator after erased element points container. create copy of iterator, increment it, delete element via copy.

if using c++11 or later, std::map::erase(...) returns iterator following last removed element, can use instead of incrementing invalid one. no need create copy of iterator use in erase in case.

for(auto ellipsepropertycounter = ellipsepropertiesmap.begin();     ellipsepropertycounter != ellipsepropertiesmap.end();     /* not increment iterator here */) {      float upperlimit = (float)m_upperfactor*(float)ellipsepropertycounter->second.radius;     float lowerlimit = (float)m_lowerfactor*(float)ellipsepropertycounter->second.radius;     if(ellipsepropertycounter->second.mindistancefromotherellipse>upperlimit                 || ellipsepropertycounter->second.mindistancefromotherellipse<lowerlimit)     {          ellipsepropertycounter = ellipsepropertiesmap.erase(ellipsepropertycounter);          radiusmapcounter = m_markerradiusmap.erase(radiusmapcounter);          markercounter = frames.markers.erase(markercounter);          goodcontourscounter = mapgoodcontours.erase(goodcontourscounter);     }     else     {          smallcontours.push_back(goodcontourscounter->second);           radiusmapcounter++;          markercounter++;          goodcontourscounter++;          ellipsepropertycounter++; // increment loop iterator in 'else' case     } }

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