{"id":1004,"date":"2018-08-05T07:19:22","date_gmt":"2018-08-05T01:49:22","guid":{"rendered":"http:\/\/www.rangakrish.com\/?p=1004"},"modified":"2018-08-05T07:27:36","modified_gmt":"2018-08-05T01:57:36","slug":"sicstus-prolog-building-a-windows-dll","status":"publish","type":"post","link":"https:\/\/www.rangakrish.com\/index.php\/2018\/08\/05\/sicstus-prolog-building-a-windows-dll\/","title":{"rendered":"Sicstus Prolog – Building a Windows DLL"},"content":{"rendered":"

Last week I upgraded to the latest version (4.4.1) of Sicstus Prolog<\/strong><\/a>\u00a0for Windows.\u00a0Since the Prolog engine can be embedded (royalty free) in other applications, it is useful to understand how to create a DLL<\/strong><\/em> (on Windows) for this purpose. In today’s article, I would like to outline this process in sufficient detail because I found the official documentation a little wanting in this area.<\/p>\n

One important point to remember: Unlike a program written in other languages such as Lisp, Go, C++<\/strong><\/em>, etc., we cannot directly<\/strong><\/em> convert a Sicstus Prolog program into a DLL<\/strong><\/em>. Instead, we have to write an intermediate layer (preferably in C\/C++) that loads a compiled Prolog program image into memory and invokes the desired predicates.<\/p>\n

The example I am going to use for this article is based on the Train.pl<\/strong><\/em> example discussed in the Sicstus.pdf<\/strong><\/em> file (page 328) available as part of the product distribution.\u00a0<\/span><\/p>\n

Instead of distributing the Prolog source program, it is common practice to generate an image file (.sav<\/strong><\/em>) from the program and load that image at runtime. Creating the image file is straightforward.<\/p>\n

\"Creating<\/a>
Creating Prolog Program Image<\/strong><\/figcaption><\/figure>\n

Creating the DLL<\/h3>\n

We need a C\/C++ program for the DLL<\/strong><\/em>. I am going to use the file Train.c<\/strong><\/em>\u00a0explained in the example. However, the example shows the steps for building a standalone .exe<\/strong><\/em> file, so I will modify it slightly for building a DLL<\/strong><\/em>. The main change is to decorate the entry point with the __declspec(dllexport)<\/strong><\/em> declaration, so that it can be called from another library. This function sets up the Prolog engine, loads the saved program image and calls the prolog predicate connected<\/strong><\/em> to generate solutions.<\/p>\n

In order to build a DLL<\/strong><\/em> from this code, we need Visual Studio 2017 (64 bit)<\/strong><\/em> compiler. I have that installed already on my machine.<\/p>\n

Next, we need the Developer Command Prompt for VS2017<\/strong><\/em>. See this<\/strong><\/a>\u00a0article to learn how to launch it.<\/p>\n

By default, this environment is configured for generating x86<\/strong><\/em> code. Since we need to build for 64 bit target, we have to run the vcvars64.bat<\/strong><\/em> file. On my machine, the file is located in G:\\Program Files (x86)\\Microsoft Visual Studio\\2017\\Professional\\VC\\Auxiliary\\Build<\/strong><\/em>\u00a0directory. Once this batch file is run, the environment is correctly set up for 64 bit target. You can check this by running the CL<\/strong><\/em> command at the prompt. See image below.<\/p>\n

\"Developer<\/a>
Developer Prompt VS2017<\/strong><\/figcaption><\/figure>\n

Lets us now CD<\/strong><\/em> to the directory where the sourse code is present. I have included Sicstus Prolog Bin directory in my System PATH<\/strong><\/em>, so that I can conveniently run the utilities without explicitly using the full path (of course, if you want, you can update the PATH<\/strong><\/em> variable each time the command prompt appears).<\/p>\n

Next, we have to run the Sicstus utility spld<\/strong><\/em> to generate the DLL<\/strong><\/em> from our source. It took me a few attempts to find out that I have to also include cmdproc.obj<\/strong><\/em> and intrpt.obj<\/strong><\/em> files to build the DLL correctly (I was getting a linker error otherwise). I created a batch file build-dll.bat<\/strong><\/em> to run spld<\/strong><\/em> with correct arguments. It is recommended to use –verbose<\/strong><\/em> option so that we can see the various steps in the process. I am including the transcript of the build process along with other files<\/a>.<\/p>\n

Once the process is complete, we will have the following files in the current (project) directory:<\/p>\n

– train.dll<\/strong><\/p>\n

– train.exp<\/strong><\/p>\n

– train.lib<\/strong><\/p>\n

– train.pdb<\/strong><\/p>\n

This completes the DLL<\/strong><\/em> creation step.<\/p>\n

Using the DLL<\/h3>\n

Let us create a C++ program to consume the DLL<\/strong><\/em> just created. Here is a simple program that does this:<\/p>\n

\"Consuming<\/a>
Consuming the DLL<\/strong><\/figcaption><\/figure>\n

As you can see, the above program dynamically loads the DLL<\/strong><\/em> and calls designated the entry point. Although it is possible to use the VS2017 IDE<\/strong><\/em> to create a project for this purpose, I chose the simpler commandline alternative. Here is the command:<\/p>\n

\n

> cl cppexample.cpp “G:\/SICStusProlog-4.4.1-VC15\/bin\/sprt4-4-1.lib” \/Fe: cppexample.exe<\/strong><\/span><\/p>\n<\/blockquote>\n

Notice that we have to include the Sicstus runtime<\/strong><\/em> library. The generated executable file is cppexample.exe<\/strong><\/em>.<\/p>\n

Running the Program<\/h3>\n

Before running the program we have to ensure that the DLL<\/strong><\/em> we created is accessible at runtime. I copied it to the current directory where the executable is located. The other file that we need in the current directory is the saved image file train.sav<\/strong><\/em>.\u00a0Sicstus Prolog runtime DLL<\/strong><\/em>\u00a0sprt4-4-1.dll<\/strong><\/em> is assumed to be in the PATH<\/strong><\/em>.<\/span><\/p>\n

Here is the output from the program:<\/p>\n

\"Running<\/a>
Running the Program<\/figcaption><\/figure>\n

Nice! The program displays the paths from Stockholm<\/strong><\/em> to Orebro <\/strong><\/em>as expected. And the Result Code<\/strong><\/em> is zero, as it should be.<\/p>\n

I hope the procedure for building and using a Sicstus Prolog DLL<\/strong><\/em> is clear from this article. All the relevant files used in this example are available\u00a0here<\/a>.<\/p>\n

Have a nice weekend!<\/p>\n

 <\/p>\n","protected":false},"excerpt":{"rendered":"

Last week I upgraded to the latest version (4.4.1) of Sicstus Prolog\u00a0for Windows.\u00a0Since the Prolog engine can be embedded (royalty free) in other applications, it is useful to understand how to create a DLL (on Windows) for this purpose. In today’s article, I would like to outline this process in sufficient detail because I found […]<\/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_post_was_ever_published":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}},"categories":[49,17,147],"tags":[149,148,150],"class_list":["post-1004","post","type-post","status-publish","format-standard","hentry","category-c","category-programming","category-prolog","tag-dll","tag-prolog","tag-sicstus"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p9OLnF-gc","jetpack-related-posts":[{"id":1025,"url":"https:\/\/www.rangakrish.com\/index.php\/2018\/08\/19\/sicstus-prolog-building-a-windows-executable\/","url_meta":{"origin":1004,"position":0},"title":"Sicstus Prolog – Building a Windows Executable","author":"admin","date":"August 19, 2018","format":false,"excerpt":"In my previous post, I showed how to build a C-based Windows DLL to execute Prolog predicates in the Sicstus Prolog\u00a0engine. 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Calling C\/C++ functions from Sicstus Prolog is fairly well documented. When it comes to C#\/.NET, the official documentation recommends the PrologBeans library. 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It is developed and supported by PDC A\/S, Denmark. So how is Visual Prolog different from other Prolog implementations out there, for example, SWI-Prolog or Sicstus Prolog? 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