C++ - Passing STL map by reference to a templated function

Question

What is wrong in this code as I am getting segmentation fault It seems returning map by value is not problematic.

#include<bits/stdc++.h>
using namespace std;

template<typename T>
T myMapIntersect(T& left, T& right)
{ }

int main()
{
    map<string, int> m;
    m["aa"] = 1;
    m["bb"] = 1;
    m["vf"] = 1;
    m["hh"] = 1;

    myMapIntersect< map<string,int> >(m, m);
    return 0;
}

OT: you probably shouldn't include directly stuff from `bits`. — Ami Tavory, Sep 28 '16 at 06:36
Because it's a convention for things that are not guaranteed to remain fixed. Hypothetically, in the next version, the file will be `bits/std_cpp.hpp`. The outer directory files would modify accordingly, and they are the ones you should directly use. — Ami Tavory, Sep 28 '16 at 06:38
See [Why should I not #include ?](http://stackoverflow.com/questions/31816095/why-should-i-not-include-bits-stdc-h) — Bo Persson, Sep 28 '16 at 06:40
It completely separates you from learning something you *should learn* : namely what constructs are provided by what headers from the standard library. Including a half-million lines of headers when all you need is `` and `` isn't instructive at all. — WhozCraig, Sep 28 '16 at 06:40

score 2 · Answer 1 · edited Sep 28 '16 at 07:18

2

You need to return in your function

#include<bits/stdc++.h>
using namespace std;

template<typename T>
T myMapIntersect(T& left, T& right)
{
    return left;
}

int main()
{
    map<string, int> m;
    m["aa"] = 1;
    m["bb"] = 1;
    m["vf"] = 1;
    m["hh"] = 1;

    myMapIntersect< map<string,int> >(m, m);
    return 0;
}

edited Sep 28 '16 at 07:18

Humam Helfawi

19,566
15
85
160

answered Sep 28 '16 at 06:55

Pavan Chandaka

11,671
5
26
34

C++ - Passing STL map by reference to a templated function

1 Answers1