153 lines
6.3 KiB
Markdown
153 lines
6.3 KiB
Markdown
## Code Structure
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I tried to make the code of the compiler and vlib as simple and readable as
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possible. One of V's goals is to be open to developers with different levels
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of experience in compiler development. Compilers don't need to be black boxes
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full of magic that only few people understand.
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The V compiler is modular, and can be used by other applications. It is located
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in `cmd/v/` and `vlib/v/`.
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The most important and useful command to remember when working on the V compiler is
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`v self`.
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It rebuilds the V compiler.
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Be careful, if you introduce a breaking change and rebuild V, you will no longer be able to use V to build
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itself. So it's a good idea to make a backup copy of a working compiler executable.
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But don't worry, you can always simply run `make`, it will download the C version of the compiler
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and rebuild it from scratch.
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The main files are:
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1. `cmd/v/v.v`. The entry point.
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- V figures out the build mode.
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- Constructs the compiler object (`struct V`).
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- Creates a list of .v files that need to be parsed.
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- Creates a parser object for each file and runs `parse()` on them.
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- The correct backend is called (C, JS, x64), and a binary is compiled.
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2. `v/scanner` The scanner's job is to parse a list of characters and convert
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them to tokens.
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3. `v/token` This is simply a list of all tokens, their string values, and a
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couple of helper functions.
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4. `v/parser` The parser. It converts a list of tokens into an AST.
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In V, objects can be used before declaration, so unknown types are marked as unresolved.
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They are resolved later in the type checker.
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5. `v/table` V creates one table object that is shared by all parsers. It
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contains all types, consts, and functions, as well as several helpers to search
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for objects by name, register new objects, modify types' fields, etc.
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6. `v/checker`. Type checker and resolver. It processes the AST and makes sure
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the types are correct. Unresolved types are resolved, type information is added
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to the AST.
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7. `v/gen` C backend. It simply walks the AST and generates C code that can be
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compiled with Clang, GCC, Visual Studio, and TCC.
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8. `json.v` defines the json code generation. This file will be removed once V
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supports comptime code generation, and it will be possible to do this using the
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language's tools.
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9. `v/gen/x64` is the directory with all the machine code generation logic. It
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defines a set of functions that translate assembly instructions to machine code
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and build the binary from scratch byte by byte. It manually builds all headers,
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segments, sections, symtable, relocations, etc. Right now it only has basic
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support of the x64 platform/ELF format.
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The rest of the directories are vlib modules: `builtin/` (strings, arrays,
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maps), `time/`, `os/`, etc. Their documentation is pretty clear.
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## Example Workflow for Contributing
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(provided by [@spytheman](https://github.com/spytheman))
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(If you don't already have a GitHub account, please create one. Your GitHub
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username will be referred to later as 'YOUR_GITHUB_USERNAME'. Change it
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accordingly in the steps below.)
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1. Fork https://github.com/vlang/v using GitHub's interface to your own account.
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Let's say that the forked repository is at
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`https://github.com/YOUR_GITHUB_USERNAME/v` .
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2. Clone the main v repository https://github.com/vlang/v to a local folder on your computer, say named nv/
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(`git clone https://github.com/vlang/v nv`)
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3. `cd nv`
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4. `git remote add pullrequest https://github.com/YOUR_GITHUB_USERNAME/v`
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NB: the remote named `pullrequest` should point to YOUR own forked repo, not the main v repository!
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After this, your local cloned repository is prepared for making pullrequests,
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and you can just do normal git operations such as: `git pull` `git status` and so on.
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5. When finished with a feature/bugfix/change, you can:
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`git checkout -b fix_alabala`
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6. `git push pullrequest` # (NOTE: the `pullrequest` remote was setup on step 4)
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7. On GitHub's web interface, go to: https://github.com/vlang/v/pulls
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Here the UI shows a dialog with a button to make a new pull request based on
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the new pushed branch.
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(Example dialog: https://url4e.com/gyazo/images/364edc04.png)
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8. After making your pullrequest (aka, PR), you can continue to work on the
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branch `fix_alabala` ... just do again `git push pullrequest` when you have more commits.
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9. If there are merge conflicts, or a branch lags too much behind V's master,
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you can do the following:
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1. `git pull --rebase origin master` # solve conflicts and do `git rebase --continue`
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2. `git push pullrequest -f` # this will overwrite your current remote branch with the updated version of your changes.
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The point of doing the above steps, is to never directly push to the main V
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repository, *only to your own fork*. Since your local `master` branch tracks the
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main V repository's master, then `git checkout master`, as well as
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`git pull --rebase origin master` will continue to work as expected
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(these are actually used by `v up`) and git can always do it cleanly.
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Git is very flexible, so there are other ways to accomplish the same thing.
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## Using Github's hub CLI tool
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You can download the `hub` tool from https://hub.github.com/ . Using
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`hub`, you will not need to go through the (sometimes) slow website
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to make PRs. Most remote operations can be done through the `hub` CLI
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command.
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NB: You still need to have a GitHub account.
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### Preparation:
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(steps 1..3 need to be done just *once*):
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1. `hub clone vlang/v my_v`
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2. `cd my_v`
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3. `hub fork --remote-name pullrequest`
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4. `git checkout -b my_cool_feature` # Step 4 is better done *once per each new feature/bugfix* that you make.
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### Improve V by making commits:
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5. `git commit -am "math: add a new function copysign"`
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### Testing your commits locally:
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You can test locally whether your changes have not broken something by
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running: `v test-compiler`
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### Publishing your commits to GitHub:
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6. `git push pullrequest`
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### Making a PR with `hub`:
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(so that your changes can be merged to the main V repository)
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7. `hub pull-request`
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Optionally, you can track the status of your PR CI tests with:
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8. `hub ci-status --verbose`
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### Fixing failing tests:
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If everything is OK, after 5-10 minutes, the CI tests should pass for
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all platforms. If not, visit the URLs for the failing CI jobs, see
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which tests have failed and then fix them by making more changes. Just use
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`git push pullrequest` to publish your changes. The CI tests will
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run with your updated code. Use `hub ci-status --verbose` to monitor
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their status.
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