{"id":2789,"date":"2022-05-04T07:10:40","date_gmt":"2022-05-04T01:40:40","guid":{"rendered":"https:\/\/www.rangakrish.com\/?p=2789"},"modified":"2022-05-04T07:16:27","modified_gmt":"2022-05-04T01:46:27","slug":"using-dll-functions-in-rust","status":"publish","type":"post","link":"https:\/\/www.rangakrish.com\/index.php\/2022\/05\/04\/using-dll-functions-in-rust\/","title":{"rendered":"Using DLL Functions in Rust"},"content":{"rendered":"

When you program in Rust<\/strong><\/em>, especially in a non-trivial project, there is a good chance that you will need to call “external”<\/strong><\/em> functions (usually, C\/C++<\/strong><\/em>) that are available in a DLL<\/strong><\/em> (we are talking about the Windows<\/strong><\/em> platform here). It could be because you wish to re-use some code that you have earlier written in C\/C++<\/strong><\/em>, or you might be calling a 3rd party library that provides some functionality you need at this point. OK, how easy is this process?<\/p>\n

As it turns out, this is not difficult at all. In this article, I will show the steps to get this integration working.<\/p>\n

First, my development environment:<\/p>\n

1) Visual Studio Professional 2022 (64 bit) 17.1.0 on Windows 10.<\/p>\n

2) Rust 1.59.0 running on Windows 10 (64 bit)<\/p>\n

3) CLion 2021.3.4 IDE with Rust Plugin<\/p>\n

Building the DLL and LIB<\/h3>\n

Although I could have assumed that we already have the DLL<\/strong><\/em> and corresponding LIB<\/strong><\/em>, let me show you how to create a simple DLL<\/strong><\/em> from scratch using Visual Studio 2022<\/em><\/strong>.<\/p>\n

1) Launch VS 2022<\/strong><\/em>. Select the option to “Create a New Project”<\/strong><\/em> and choose the type as “DLL”. <\/strong><\/em>Click “Next”.<\/strong><\/em><\/p>\n

\"New<\/a>
New DLL Project<\/strong><\/figcaption><\/figure>\n

2) Then specify the Project Name<\/strong><\/em> and Location<\/strong><\/em> and click “Create”<\/strong><\/em>:<\/p>\n

\"Project<\/a>
Project Name and Location<\/strong><\/figcaption><\/figure>\n

3) This will result in the auto generation of project files, including a bare-bones “dllmain.cpp”<\/strong><\/em> file:<\/p>\n

\"Generated<\/a>
Generated Code<\/strong><\/figcaption><\/figure>\n

Let us delete the generated function and type in our function, which will be called from Rust<\/strong><\/em>:<\/p>\n

\"Our<\/a>
Our Exported Function<\/strong><\/figcaption><\/figure>\n

The extra qualifiers before the function reurn type ensure that this will be exported from the DLL<\/strong><\/em> without any name mangling.<\/p>\n

4) Make sure the target is “x64”<\/strong><\/em>. Additionally, for our example, we will choose “Release”<\/strong><\/em> mode.<\/p>\n

5) Build the project. This will result in the files “DllExample.dll”<\/strong><\/em> and “DllExample.lib”<\/strong><\/em> being created in “x64\\Release”<\/strong><\/em> sub-directory within the project directory.<\/p>\n

We need the above two files when we build our Rust<\/strong><\/em> project in CLion<\/strong><\/em>.<\/p>\n

Rust Example that Uses the DLL<\/h3>\n

We now launch CLion<\/strong><\/em> and create a New Rust<\/strong><\/em> project. Here is the actual Rust<\/strong><\/em> code we will be using:<\/p>\n

\"Rust<\/a>
Rust Code<\/strong><\/figcaption><\/figure>\n

Since we are making a call to an external<\/strong><\/em> function, we have to declare the equivalent function signature in Rust<\/strong><\/em>, and also specify the external library to use. Notice that we are indicating the “kind”<\/strong><\/em> as “static”<\/strong><\/em> since we will be linking the Rust<\/strong><\/em> code with our DllExample.lib<\/strong><\/em><\/p>\n

Another important thing to note in the above code is the use of “unsafe”<\/strong><\/em> block. This is required since an external (non-Rust<\/em><\/strong>) code might have “unsafe”<\/strong> behavior<\/strong><\/em>.<\/p>\n

Before we build the Rust<\/strong><\/em> project, we need to copy our DllExample.lib<\/strong><\/em> file to a location that can be configured in the “LIB”<\/strong><\/em> path. This is what I did:<\/p>\n

a) Copied the LIB file to the Rust<\/strong><\/em> project directory. Here are the files in this directory:<\/p>\n

\"LIB<\/a>
LIB File Directory<\/strong><\/figcaption><\/figure>\n

Then I updated the “LIB”<\/strong><\/em> environment variable to include the path: “F:\\Rust Projects\\CallingDLL\\”<\/strong><\/em><\/p>\n

b) Copied the DllExample.dll<\/strong><\/em> file to the “debug”<\/strong><\/em> subdirectory under “target”<\/strong> <\/em>directory:<\/p>\n

\"Executable<\/a>
Executable and DLL<\/strong><\/figcaption><\/figure>\n

This is required in order to run the final Executable<\/strong><\/em> file.<\/p>\n

We can now build and run the Rust<\/em><\/strong> project.\u00a0<\/span><\/p>\n

Here is the program output as it appears within CLion IDE<\/strong><\/em>:<\/p>\n

\"Program<\/a>
Program Output<\/strong><\/figcaption><\/figure>\n

This shows that our external function in the DLL<\/strong><\/em> is called from within Rust<\/strong><\/em>. You can download the relevant files from here<\/strong><\/em><\/a>.<\/p>\n

That was straightforward, right? You may find this<\/strong><\/em><\/a> article useful if you would like to explore “Foreign Function Interface (FFI)”<\/strong><\/em> of Rust<\/strong><\/em> in greater detail.<\/p>\n

Have a nice week!<\/p>\n","protected":false},"excerpt":{"rendered":"

When you program in Rust, especially in a non-trivial project, there is a good chance that you will need to call “external” functions (usually, C\/C++) that are available in a DLL (we are talking about the Windows platform here). It could be because you wish to re-use some code that you have earlier written in […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"advanced_seo_description":"","jetpack_seo_html_title":"","jetpack_seo_noindex":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[49,17,314],"tags":[67,149,320,317],"class_list":["post-2789","post","type-post","status-publish","format-standard","hentry","category-c","category-programming","category-rust","tag-c","tag-dll","tag-ffi","tag-rust"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p9OLnF-IZ","jetpack-related-posts":[{"id":3070,"url":"https:\/\/www.rangakrish.com\/index.php\/2023\/04\/02\/building-v-language-dll\/","url_meta":{"origin":2789,"position":0},"title":"Building V Language DLL","author":"admin","date":"April 2, 2023","format":false,"excerpt":"The relatively new V Programming Language (Vlang) boasts of some interesting features such as \u201cfast compilation\u201d and runtime performance \u201cas fast as C\u201d, at the same time being a \u201csimple language\u201d. 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DLang\u00a0has been around since 2001. It was originally created by Walter Bright and later Andrei Alexandrescu joined the team in 2007. 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In today's post, I would like to explain how to go in the other direction, namely, how to call Lisp functins from Go. There are two ways to do this. 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