Double pointer as parameter - c++

Question

I have the follow prototype:
int Split(const char* str, const char* delim,unsigned int& numtokens,char **tokensRes)
The last parameter is used to return the response of this function. In the function we have the follow:
.
.
char **tokens =(char**) calloc(tokens_alloc, sizeof(char*));
.
.
.
//at the end of the code
tokensRes = tokens;
.
When returns the value of tokens variable direct when the return of the function is char** I receive the correct answer, but using the method above the return of the function came empty. How can I make this function work correctly?
EDIT 1:
My intent is receive an array of char arrays, eg:
array[0] = "ABC"
array[1] = "ABC"
array[2] = "ABC"
array[3] = "ABC"

Answer 1

Change the prototype from:
int Split(const char* str, const char* delim,unsigned int& numtokens,char **tokensRes)
To:
int Split(const char* str, const char* delim,unsigned int& numtokens,char ** &tokensRes)
And the code tokensRes = tokens; will work. To understand why learn more about C++ and references.
Other answers about using strings are valid if you're planning to move from a C style of coding to a C++ one. The ease of coding would improve a lot and no worries about memory management and pointers (well not often), which are done automatically by classes. No worries about a performance decrease either as long as you follow good practices such as passing objects by reference and not value.

Answer 2

Assuming you want to return an array of strings (char**), then you need to pass a pointer to such an array that you can assign. That is, you need to pass a char*** and assign it like *tokensRes = tokens.

Answer 3

Just ditch the plain C types and use C++ types:
std::vector<std::string> Split(std:;string const& str, std::string const& delim, unsigned int& numtokens);
If you have to stick to the C interface, you need an additional indirection with a triple pointer (I am assuming that you want to return an array of token strings).
int Split(const char* str, const char* delim,unsigned int& numtokens,char ***tokensRes)
char** tokens;
Split("String;String", ";", 2, &tokens);
I really dislike output parameters, and I always wonder why anybody does not use std::string in C++.
Tokenizing has been implemented in many libraries, e.g. in boost::split or boost::tokenizer. No need to reinvent the wheel:
// simple_example_1.cpp
#include<iostream>
#include<boost/tokenizer.hpp>
#include<string>
int main(){
using namespace std;
using namespace boost;
string s = "This is, a test";
tokenizer<> tok(s);
for(tokenizer<>::iterator beg=tok.begin(); beg!=tok.end();++beg){
cout << *beg << "\n";
}
}
The output from simple_example_1 is:
This
is
a
test