Question

I have a function which creates an array of Maps:

map<string, int> *pMap

And a function which writes maps to the array:

int iAddMap(map<string, int> mapToAdd, map<string, int> *m, int i)
{
    m = &(pMap[i]);
    memcpy(m, mapToAdd, sizeof(map<string, int>));
}

And a function to get maps from the array

map<string, int>& getMap(int i)
{
    return pMap[i];
}

I can write maps to the array without any issue, but every get call results in a seg fault:

int val; 
// val defined after this
map<string, int> * pGetMap = &(getMap(val));

Any suggestions on why this is happening?

Answer 1

You cannot use memcpy() to copy objects like maps, or indeed any other kind of C++ container – you need to use assignment, which takes into account the map’s underlying structure and se,mantics. And you should be using a vector <map>, as you actually seem to want a copy rather than a pointer.