A beginner's guide to using C++ Modules in Visual Studio

15 Sep 2023

VisualStudio

C++ Modules are a new feature introduced in the C++20 standard that simplify the organization and compilation of C++ code. They provide a way to encapsulate code into reusable modules, speeding up compilation times and improving code maintainability. In this guide, we’ll explore how to use C++ Modules in Visual Studio to enhance your C++ development experience.

What are C++ Modules?

Traditionally, C++ code is organized into header files and implementation files. When a header file is included in multiple source files, it can lead to redundant compilations and longer build times. C++ Modules aim to solve this problem by allowing you to specify which parts of your code are reusable and can be compiled independently.

A module is a named entity that contains a collection of related code. It can export a set of symbols which other modules can import, enabling efficient reusability of code. By using modules, you can reduce the need for including header files and minimize redundant compilations.

Setting up Visual Studio for C++ Modules

To start using C++ Modules in Visual Studio, you need to ensure that you have the necessary version installed. C++ Modules support was added in Visual Studio 2019 version 16.9 or later. If you have an older version, consider updating to the latest version.

Once you have the appropriate version of Visual Studio, follow these steps to enable C++ Modules:

Create a new C++ project or open an existing one in Visual Studio.
Right-click on your project in the Solution Explorer and select “Properties” from the context menu.
In the project properties, navigate to “C/C++” -> “Language” -> “C++ Language Standard” and select “ISO C++ Latest Draft Standard (/std:c++latest)”.
Under the same “C/C++” section, go to “Command Line” and add “/experimental:module” to the “Additional Options” field.

With these settings, Visual Studio is now configured to build and use C++ Modules in your project.

Creating and Using C++ Modules

To create a C++ Module in Visual Studio, you’ll need to follow these steps:

Create a new header file (.h) or source file (.cpp) in your project.
Use the module keyword to declare the file as a module, followed by the module name.
```
module MyModule;
```
Inside the module, you can import necessary dependencies using the import keyword.
```
import <iostream>;
```
Declare any module-level exports using the export keyword.
```
export void myFunction();
```

Define the exported functions or variables within the module implementation file (.cpp).

void myFunction() {
    std::cout << "Hello from myFunction!" << std::endl;
}

Import the module in other parts of your code using the import keyword.
```
import MyModule;
```
Use the exported functions or variables from the imported module.
```
myFunction();
```

By utilizing C++ Modules, you can now organize and reuse your code more effectively, resulting in reduced compilation times and improved code maintenance.

Conclusion

C++ Modules provide a modern approach to organizing and compiling C++ code. With Visual Studio’s support, you can take advantage of this feature to enhance your C++ development experience. By following the steps outlined in this guide, you can start using C++ Modules in your Visual Studio projects and reap the benefits of faster builds and improved code organization.

#C++ #VisualStudio