Introduction to threads in C++
Threads in the C++ programming language are an advanced concept or feature in modern C++ programming that allows programs to run source code created in a C++ program by grouping them together. In C++, threads are natively supported through the C++ Standard Library since version C++11. Multithreading in a C++ program allows multiple programming tasks to run simultaneously, which can improve program development performance, especially when performing multi-core processing in a C++ program. As such, threads in C++ programs can lead to complex programming issues such as synchronization, race conditions, and deadlocks.
So, let’s explore the concept of threads in C++ programming.
What is a thread in C++ programming?
In a C++ program, a thread is a unit task that runs within a process system. A program can define or create multiple threads within a single process, and all threads within that process share or use memory space simultaneously. In a C++ program, user-created threads allow simultaneous execution of program source code. This means that multiple threads can run simultaneously within an existing program on a multi-core processor.
Element of a thread in C++.
- Main thread – In a C++ program, this is the main thread that starts running when the program is launched.
- Worker threads – In a C++ program, these are additional threads that can work concurrently with the main thread.
In a C++ program, user-defined class threads are managed or used by invoking the std::thread class defined in the <thread> header file.
Creating and launching threads in a C++ program.
To create and run threads in C++ programs, C++ users use the std::thread class header file. C++ users pass a function (or callable object) to the std::thread constructor in a program, which will execute a new thread.
Basic syntax for creating a thread in C++.
#include <iostream>
#include <thread>
void testFunction() {
std::cout << “Welcome to Vcanhelpsu Edtech” << std::endl;
}
int main() {
// Here we create a thread that calls the function `testFunction`
std::thread t(testFunction);
// Here it waits for the thread to finish first
t.join(); // Here it blocks until thread t completely finishes
return 0;
}
Explanation of syntax for creating a thread in C++.
- In this example, std::thread t(testFunction) creates a new thread that executes testFunction.
- The t.join() function ensures that the main thread waits for the newly created thread to finish before proceeding. If C++ users do not call join, the program may terminate before the thread completes.
Passing arguments to threads in a C++ program.
C++ users can pass arguments to the function in which the thread is running by providing user-defined constructor parameters to the std::thread class.
Example of passing thread arguments in C++.
#include <iostream>
#include <thread>
void displayTotal(int p, int q) {
std::cout << “The total of the p and q variables is – ” << p + q << std::endl;
}
int main() {
int m = 9;
int n = 12;
// Here, pass arguments to the thread’s displayTotal function
std::thread t(displayTotal, m, n);
t.join(); // Here, wait for the thread to finish first
return 0;
}
Explanation of passing thread arguments in C++.
- In this example, the displayTotal function takes two int parameters, p and q, as input. These are passed to a new thread when it is created.
- Here the variables p and q are passed to the displayTotal function by value.
