Sphinx Quickstart Template

This article is intended to take someone in the state of “I want to write documentation and get it added to LLVM’s docs” and help them start writing documentation as fast as possible and with as little nonsense as possible.

Overview

LLVM documentation is written in reStructuredText, a markup syntax similar to markdown (but much more powerful). The LLVM documentation site itself uses Sphinx, a documentation generator originally written for Python documentation.

How to use this template

This article is located in docs/SphinxQuickstartTemplate.rst. To use it as a template, make a copy and open it in a text editor. You can then write your docs, and then send the new article to llvm-commits for review.

To view the restructuredText source file for this article, click Show Source on the right sidebar.

Authoring Guidelines

Focus on content. It is easy to fix the Sphinx (reStructuredText) syntax later if necessary, although reStructuredText tries to imitate common plain-text conventions so it should be quite natural. A basic knowledge of reStructuredText syntax is useful when writing the document, so the last ~half of this document (starting with Example Section) gives examples which should cover 99% of use cases.

Let me say that again: focus on content. But if you really need to verify Sphinx’s output, see docs/README.txt for information. Once you have finished with the content, please send the .rst file to llvm-commits for review.

Creating New Articles

Before creating a new article, consider the following questions:

  1. Why would I want to read this document?

  2. What should I know to be able to follow along with this document?

  3. What will I have learned by the end of this document?

A standard best practice is to make your articles task-oriented. You generally should not be writing documentation that isn’t based around “how to” do something unless there’s already an existing “how to” article for the topic you’re documenting. The reason for this is that without a “how to” article to read first, it might be difficult for someone unfamiliar with the topic to understand a more advanced, conceptual article.

When creating a task-oriented article, follow existing LLVM articles by giving it a filename that starts with HowTo*.rst. This format is usually the easiest for another person to understand and also the most useful.

Focus on content (yes, I had to say it again).

The rest of this document shows example reStructuredText markup constructs that are meant to be read by you in your text editor after you have copied this file into a new file for the documentation you are about to write.

Example Section

An article can contain one or more sections (i.e., headings). Sections (like Example Section above) help give your document its structure. Use the same kind of adornments (e.g. ====== vs. ------) as are used in this document. The adornment must be the same length as the text above it. For Vim users, variations of yypVr= might be handy.

Example Nested Subsection

Subsections can also be nested beneath other subsections. For more information on sections, see Sphinx’s reStructuredText Primer.

Text Formatting

Text can be emphasized, bold, or monospace.

To create a new paragraph, simply insert a blank line.

Lists

restructuredText allows you to create ordered lists…

  1. A list starting with #. will be automatically numbered.

  2. This is a second list element.

    1. Use indentation to create nested lists.

…as well as unordered lists:

  • Stuff.

    • Deeper stuff.

  • More stuff.

Code Blocks

You can make blocks of code like this:

int main() {
  return 0;
}

For a shell session, use a console code block (some existing docs use bash):

$ echo "Goodbye cruel world!"
$ rm -rf /

If you need to show LLVM IR use the llvm code block.

define i32 @test1() {
entry:
  ret i32 0
}

Some other common code blocks you might need are c, objc, make, and cmake. If you need something beyond that, you can look at the full list of supported code blocks.

However, don’t waste time fiddling with syntax highlighting when you could be adding meaningful content. When in doubt, show preformatted text without any syntax highlighting like this:

                      .
                       +:.
                   ..:: ::
                .++:+:: ::+:.:.
               .:+           :
        ::.::..::            .+.
      ..:+    ::              :
......+:.                    ..
      :++.    ..              :
        .+:::+::              :
        ..   . .+            ::
                 +.:      .::+.
                  ...+. .: .
                     .++:..
                      ...

Generating the documentation

You can generate the HTML documentation from the sources locally if you want to see what they would look like. In addition to the normal build tools you need to install Sphinx and the necessary extensions using the following command inside the llvm-project checkout:

pip install --user -r ./llvm/docs/requirements.txt

Then run cmake to build the documentation inside the llvm-project checkout:

mkdir build
cd build
cmake -DLLVM_ENABLE_SPHINX=On ../llvm
cmake --build . --target docs-llvm-html

In case you already have the Cmake build set up and want to reuse that, just set the CMake variable LLVM_ENABLE_SPHINX=On.

After that you find the generated documentation in build/docs/html folder.