Why Doesn’t C++ Contain Built-In Support for Multithreading?

C++ does not contain any built-in support for multithreaded applications. Instead, it relies entirely upon the operating system to provide this feature. Given that both Java and C# provide built-in support for multithreading, it is natural to ask why this isn’t also the case for C++. The answers are efficiency, control, and the range of applications to which C++ is applied. Let’s examine each.

By not building in support for multithreading, C++ does not attempt to define a “one size fits all” solution. Instead, C++ allows you to directly utilize the multithreading features provided by the operating system. This approach means that your programs can be multithreaded in the most efficient means supported by the execution environment. Because many multitasking environments offer rich support for multithreading, being able to access that support is crucial to the creation of high-performance, multithreaded programs.

Using operating system functions to support multithreading gives you access to the full range of control offered by the execution environment. Consider Windows. It defines a rich set of thread-related functions that enable finely grained control over the creation and management of a thread. For example, Windows has several ways to control access to a shared resource, including semaphores, mutexes, event objects, waitable timers, and critical sections. This level of flexibility cannot be easily designed into a language because the capabilities of operating systems differ. Thus, language-level support for multithreading usually means offering only a “lowest common denominator” of features. With C++, you gain access to all the features that the operating system provides. This is a major advantage when writing high-performance code.

C++ was designed for all types of programming, from embedded systems in which there is no operating system in the execution environment to highly distributed, GUI-based end-user applications and everything in between. Therefore, C++ cannot place significant constraints on its execution environment. Building in support for multithreading would have inherently limited C++ to only those environments that supported it and thus prevented C++ from being used to create software for nonthreaded environments.

In the final analysis, not building in support of multithreading is a major advantage for C++ because it enables programs to be written in the most efficient way possible for the target execution environment. Remember, C++ is all about power. In the case of multithreading, it is definitely a situation in which “less is more.”