Passing array as argument to std::thread - c++

Question

I'm having difficulty passing an array of integers to a function using std::thread. It seems like thread doesn't like the array portion of it. What other way is there to pass an array to a threaded function?
#include <thread>
#include <ostream>
using namespace std;
void process(int start_holder[], int size){
for (int t = 0; t < size; t++){
cout << start_holder[t] << "\n";
}
}
int main (int argc, char *argv[]){
int size = 5;
int holder_list[size] = { 16, 2, 77, 40, 12071};
std::thread run_thread(process,holder_list,size);
//std::ref(list) doesnt work either
//nor does converting the list to std::string then passing by std::ref
run_thread.join();
}

Answer 1

Since you are using C++ start using std::vector or std::list instead of the c-style arrays. There are many other container types as well. If you want a fixed size array use std::array instead (since C++11).
These containers have functions to get the size so you do not need to send it through as a separate argument.
#include <thread>
#include <iostream>
#include <vector>
void process(std::vector<int> start_holder){
for(int t = 0; t < start_holder.size(); t++){
std::cout << start_holder[t] << "\n";
}
// Or the range based for
for(int t: start_holder) {
std::cout << t << "\n";
}
}
int main (int argc, char *argv[]){
std::vector<int> holder_list{ 16, 2, 77, 40, 12071};
std::thread run_thread(process, holder_list);
run_thread.join();
}

Answer 2

Make size constant:
#include <thread>
#include <iostream>
void process(int* start_holder, int size){
for (int t = 0; t < size; t++){
std::cout << start_holder[t] << "\n";
}
}
int main (int argc, char *argv[]){
static const int size = 5;
int holder_list[size] = { 16, 2, 77, 40, 12071};
std::thread run_thread(process, holder_list, size);
run_thread.join();
}
If size is variable, int arr[size] is not a standard C++. It is a variable array extension to the language as your compiler says in the error and is not compatible with int* aka int [].