能够从 stl 遍历 c++ map，但无法分配值或打印出 ZA2F2ED4F8EBC04614C21A2DDC 变量

Question

I am currently trying to use the map provided from the c++ stl. My key value pair are both a pointer to a custom object. I am able to store data into the map, and also successfully iterate through all the keys and values of the map. However, whenever I attempt to access one of the values member variables in the map through its key I get the following runtime error:

Segmentation fault (core dumped)

I am using a custom comparator for the map. I believe this is where the issue is arising. I believe this becasue whenever I run the code without the custom comparator the error goes away.

Note that the use of the Eigen library is just being used for linear algebra purposes. Please try to look past it in the example code, as it is just being used in my particular implementation to the problem I am trying to solve.

Please use the following code for context:

 #include <iostream> #include <map> #include <Eigen/Dense> #include <vector> #include "A_star.h" using namespace std; struct NodeCostPointer { bool operator()(star::Node* const& a,star::Node* const& b){ return a->f_cost >= b->f_cost; int main() { Eigen::Matrix<float,3,3> obj; obj(0,0) = 3360; obj(1,0) = 3360; obj(2,0) = 3360; obj(0,1) = 7000; obj(1,1) = 7000; obj(2,1) = 7000; obj(0,2) = 5280; obj(1,2) = 5280; obj(2,2) = 5280; Eigen::Matrix<float,3,1> end; end(0) = 12300; end(1) = 12300; end(2) = 12300; Eigen::Matrix<float,3,1> start; start(0) = -.8; start(1) = -.8; start(2) = -.8; map<star::Node*,star::Node*, NodeCostPointer> test; star::Node* nodetest = new star::Node(start,6,0); star::Node* nodetest2 = new star::Node(end,6,0); star::Node* nodetest3 = new star::Node(start,5,std::numeric_limits<float>::infinity()); test[nodetest] = nodetest3; test[nodetest2] = nodetest3; // error occurs here: cout << test[nodetest]->f_cost << endl; // or test[nodetest]->f_cost = 4; map<star::Node*,star::Node*,NodeCostPointer>::iterator itt; for(itt=test.begin();itt.=test;end();itt++){ cout << itt->first->cordinates << endl; cout << " \n"; } return 0

Implementation of Node class:

 star::Node::Node(Eigen::Matrix<float,3,1> _cordinates, float _h_cost, float _g_cost): cordinates {_cordinates}, h_cost {_h_cost}, g_cost {_g_cost}{ f_cost = h_cost+g_cost; obstical = false; closedNode = false; };

Answer 1

Thank you @timl and others for pointing me the correct direction. The problem was due to not satisfying the strict weak ordering requirement for comparison. Changing the comparator to the following seems to have made everything work:

 struct NodeCostPointer { bool operator()(star::Node* const& a,star::Node* const& b){ return std::tie(a->f_cost,a->h_cost,a->cordinates(0)) < std::tie(b->f_cost,b->h_cost,b->cordinates(0)); }

After learning about how this notation works I decided to add additional things for comparison ie h_cost and coordinates. However, not including them would have of course also worked.