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120 lines
3.2 KiB
Markdown
120 lines
3.2 KiB
Markdown
# Compiler pipeline
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A simple high level explanation
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how the compiler pipeline (`parser` -> `checker` -> `generator`) works.
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## Reading files
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### Getting builtin files
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To load all builtin files,
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a preference `Preferences.lookup_path` for the path where to look for exists.
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See `Builder.get_builtin_files` as example.
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If the file is a `.vsh` file and the backend is C, `vlib/os` will also be loaded as builtin.
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### Getting project files
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Either there is a specific file: `my_file.v` or a directory containing V files.
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In the last case it scans that directory for all files.
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See `Builder.v_files_from_dir` as the helper method.
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This list of files needs to be filtered so that only `*.v` files exist.
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Skips the following file types:
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- `*_test.v`
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- either `*.c.v` or `*.c.js` depending on the backend
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- all files that doesn't end with `.v`
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- Files that are not defined in `Preferences.compile_defines`
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or `Preferences.compile_defines_all` **if any file is defined**.
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## Parsing files
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To parse something a new template is created as the first step:
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```v
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import v.ast
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table := ast.new_table()
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```
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a new preference is created:
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```v
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import v.pref
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pref := &pref.Preferences{}
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```
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and a new scope is created:
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```v
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import v.ast
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scope := ast.Scope{
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parent: 0
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}
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```
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after that, you can parse your files.
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## Parse text
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If you want to parse only text which isn't saved on the disk you can use this function.
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```v oksyntax
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import v.parser
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code := ''
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// table, pref and scope needs to be passed as reference
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parsed_file := parser.parse_text(code, table, .parse_comments, &pref, &scope)
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```
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## Parse a single file
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For parsing files on disk, a path needs to be provided.
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The paths are collected one step earlier.
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```v oksyntax
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import v.parser
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path := ''
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// table, pref and scope needs to be passed as reference
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parsed_file := parser.parse_file(path, table, .parse_comments, &pref, &scope)
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```
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## Parse a set of files
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If you have a batch of paths available which should be parsed,
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there is also a function which does all the work.
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```v oksyntax
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import v.parser
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paths := ['']
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// table, pref and scope needs to be passed as reference
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parsed_files := parser.parse_files(paths, table, &pref, &scope)
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```
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## Parse imports
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A file often contains imports. These imports might need to be parsed as well.
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The builder contains a method which does this: `Builder.parse_imports`.
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If the module which is imported isn't parsed already,
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you have to collect it relatively from the main file.
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For this the `ast.File` contains a list of imports.
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Those imports needs to be found on disk.
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`.` is just replaced with seperators in the relative location of the main file.
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Then all files from that directory are collected and parsed again like the previous steps explained.
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## Checking AST
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A new checker is created:
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```v oksyntax
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import v.checker
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mut checker := checker.new_checker(table, &pref)
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```
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After checking your files in `checker.errors` and `checker.warnings` you can see the results.
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### Check `ast.File`
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```v oksyntax
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checker.check(parsed_file)
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```
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### Check a list of `ast.File`
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```v oksyntax
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checker.check_files(parsed_files)
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```
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## Generate target from AST
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Generating C code works just as this:
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```v oksyntax
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import v.gen.c
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res := c.gen(parsed_files, table, &pref)
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```
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