Question

I have a map<key_t, struct tr_n_t*> nodeTable and I’m trying to perform nodeTable[a] = someNode where a is of type typedef long key_t and someNode is of type o_t*.

I get a segmentation fault at the following point in the execution in stl_function.h:

  /// One of the @link comparison_functors comparison functors@endlink.
  template<typename _Tp>
    struct less : public binary_function<_Tp, _Tp, bool>
    {
      bool
      operator()(const _Tp& __x, const _Tp& __y) const
      { return __x < __y; }
    };

Source code:

#include <stdio.h>
#include <stdlib.h>
#include <map>

using namespace std;

typedef long key_t;

typedef struct tr_n_t {
    key_t key;
    map<key_t, struct tr_n_t *> nodeTable;
} o_t;

int main() {
    o_t *o = (o_t *) malloc(sizeof(o_t));
    o->nodeTable[1] = o;
    return 0;
}

Am I not using the map right?

Answer 1

The problem is that because you initialize o using malloc, its memory is allocated but its constructor isn’t invoked.

Change it to o_t *o = new o_t(); because using new instead of malloc will invoke the map’s constructor.