{"id":3840,"date":"2020-05-15T14:58:01","date_gmt":"2020-05-15T12:58:01","guid":{"rendered":"https:\/\/mariusbancila.ro\/blog\/?p=3840"},"modified":"2020-05-15T14:58:01","modified_gmt":"2020-05-15T12:58:01","slug":"modules-in-clang-11","status":"publish","type":"post","link":"https:\/\/mariusbancila.ro\/blog\/2020\/05\/15\/modules-in-clang-11\/","title":{"rendered":"Modules in Clang 11"},"content":{"rendered":"

In my previous post<\/a>, I wrote about the support for C++20 modules in Visual Studio 2019 16.5. VC++ is not the only major compiler that has experimental support for modules. Clang has its own implementation, although only partial. In this post, I will discuss the support available in Clang 11. You can check the current status here<\/a>.<\/p>\n

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Disclaimer: My experience with Clang is limited to compiling various snippets of code. Although documentation may exist in some inner circle of trust, it is not easily found using search engines. The content of this article was put together from several bits of information found online and large amounts of trial and error. Therefore, the information I present below may not be complete (although I hope it is correct). If you find anything that needs to be complemented or corrected, please leave a comment and I will update accordingly.<\/p>\n

A first example<\/h2>\n

Let’s start again with the typical hello world application in C++ that looks as follows: <\/p>\n

#include <iostream>\r\n\r\nint main()\r\n{\r\n    std::cout << \"Hello, World!\\n\";\r\n}<\/pre>\n
To compile this with Clang you need to run the following command:<\/p>\n
clang++ -Wall -std=c++2a -stdlib=libc++ main.cpp -o main<\/pre>\n
Noticed that I specified -std=c++2a<\/tt> to indicate support for C++20, although any other version would have worked. However, this switch is required to enable modules support, which used to be available only by specifying -fmodules-ts<\/tt>. This is now no longer necessarily when compiling with -std=c++2a<\/tt>.<\/p>\n
This program can be modified to use modules instead by replacing the #include<\/tt> preprocessor directive with an import<\/tt> directive, as follows:<\/p>\n
import <iostream>;\r\n\r\nint main()\r\n{\r\n    std::cout << \"Hello, World!\\n\";\r\n}<\/pre>\n
Compiling this program requires some changes to the command we executed previously.<\/p>\n
clang++ -Wall -std=c++2a -stdlib=libc++ -fimplicit-modules -fimplicit-module-maps main.cpp -o main<\/pre>\n
So, what do these additional arguments represent?<\/p>\n