# @willbooster/tree-sitter-cpp
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[](https://crates.io/crates/willbooster-tree-sitter-cpp)
C++ grammar for [tree-sitter](https://github.com/tree-sitter/tree-sitter), forked from
[tree-sitter/tree-sitter-cpp](https://github.com/tree-sitter/tree-sitter-cpp). We are grateful
to its authors and contributors. This is not an official release of that project.
This fork fixes parsing bugs and raises conformance with the ISO C++ standard
([working draft](https://eel.is/c++draft/)).
## Language coverage
The parser uses one grammar for syntax from C++98 onward, including syntax from the linked working draft. It has no
compiler-style `-std` selection and does not guarantee complete conformance to any edition. The corpus provides
examples of the forms it accepts:
| C++98/03 declarations and classes | [Declarations](test/corpus/declarations.txt) |
| C++11 lambdas and C++14 generic lambdas | [Expressions](test/corpus/expressions.txt) |
| C++17 structured bindings | [Declarations](test/corpus/declarations.txt) |
| C++20 concepts, requires clauses and requires expressions | [Concepts](test/corpus/concepts.txt) |
| C++20 modules, partitions, imports and exports | [Modules](test/corpus/modules.txt) |
| C++23 consteval if statements | [Statements](test/corpus/statements.txt) |
| Working-draft function contracts | [Contracts](test/corpus/contracts.txt) |
| Working-draft reflection, splice syntax and annotations | [Reflection](test/corpus/reflection.txt) |
| Microsoft declaration specifiers and calling conventions | [Microsoft extensions](test/corpus/microsoft.txt) |
The tree describes the written source. Preprocessing branches remain in the tree; macro expansion, condition
evaluation and header inclusion are left to a preprocessor. Name lookup, type checking and other semantic validation
are left to a compiler. In ambiguous declaration and expression syntax, the chosen tree can therefore differ from
the compiler's interpretation.
## Support Scope
This fork maintains only full parsing: valid input yields a correct tree, and invalid input yields `ERROR` or `MISSING`
nodes without crashing, hanging, or taking more than linear time. Incremental parsing works as in upstream tree-sitter
but is not tested here, and no queries (highlights, locals, injections, tags) are shipped. Node types, field names, and
the trees that error recovery produces may change; such changes are released as new major versions.
## Usage
The npm package ships `tree-sitter-cpp.wasm` for
[@willbooster/web-tree-sitter](https://www.npmjs.com/package/@willbooster/web-tree-sitter), which runs in Node.js, Bun,
browsers, and Cloudflare Workers. Use runtime version 17.0.1 or later within major version 17. The parser uses the
WillBooster/tree-sitter ABI `0x5742000c`; upgrade the grammar and runtime together. Install both:
```sh
npm install @willbooster/tree-sitter-cpp @willbooster/web-tree-sitter
```
In Node.js and Bun, load the `.wasm` file from its path:
```js
import { fileURLToPath } from 'node:url';
import { Language, Parser } from '@willbooster/web-tree-sitter';
await Parser.init();
const parser = new Parser();
const wasmPath = fileURLToPath(import.meta.resolve('@willbooster/tree-sitter-cpp/tree-sitter-cpp.wasm'));
parser.setLanguage(await Language.load(wasmPath));
const tree = parser.parse('int main() {}\n');
```
In browsers, serve both `.wasm` files and load them by URL. With Vite:
```js
import cppUrl from '@willbooster/tree-sitter-cpp/tree-sitter-cpp.wasm?url';
import { Language, Parser } from '@willbooster/web-tree-sitter';
import runtimeUrl from '@willbooster/web-tree-sitter/web-tree-sitter.wasm?url';
await Parser.init({ locateFile: () => runtimeUrl });
const parser = new Parser();
parser.setLanguage(await Language.load(cppUrl));
```
In Cloudflare Workers, which do not allow compiling Wasm at run time, import both `.wasm` files as modules:
```js
import cpp from '@willbooster/tree-sitter-cpp/tree-sitter-cpp.wasm';
import { Language, Parser } from '@willbooster/web-tree-sitter';
import runtime from '@willbooster/web-tree-sitter/web-tree-sitter.wasm';
await Parser.init({ wasmModule: runtime });
const parser = new Parser();
parser.setLanguage(await Language.load(cpp));
```
The package also ships the node types in `src/node-types.json`.
In Rust, depend on the [crate](https://crates.io/crates/willbooster-tree-sitter-cpp) and on
[willbooster-tree-sitter](https://crates.io/crates/willbooster-tree-sitter), the runtime this package is tested and
fuzzed with. Use runtime version 17.0.1 or later within major version 17:
```sh
cargo add --rename tree-sitter willbooster-tree-sitter@17.0.1
cargo add --rename tree-sitter-cpp willbooster-tree-sitter-cpp
```
```rust
let mut parser = tree_sitter::Parser::new();
parser.set_language(&tree_sitter_cpp::LANGUAGE.into())?;
```
The crate ships the same `tree-sitter.json` as the npm package.
## Development
```sh
mise install
bun install --frozen-lockfile
bun run build/ci
bun run test
script/parse-examples
cargo test --locked
```
The scripts and tests generate, build, test, and parse with `script/tree-sitter`, the tree-sitter CLI of the
WillBooster/tree-sitter runtime version locked in `Cargo.lock`, since the generator and the runtime of upstream's CLI are
not the ones this package ships with. Its first run downloads that CLI from the runtime's GitHub Release, or builds it
with `cargo` (whose build runs the CMake that `mise.toml` pins) when the download fails or the release has no binary
that runs here. Run other CLI commands through it as well (e.g. `script/tree-sitter parse file.cpp`).
`bun run generate` records a fresh generation profile from the applicable `test/corpus` cases and Git-tracked
files in `examples/`, then generates compact parser tables. The parser also embeds metadata from `tree-sitter.json`. After changing a grammar, the pinned `@willbooster/tree-sitter-c` dependency,
`tree-sitter.json`, a corpus case, or a tracked example,
regenerate and commit `src/`. Stage added or removed examples with `git add -A examples` before generation so the profile uses the intended file list.
Profiles in `.tmp/generation-profiles/` are temporary and must not be committed. `bun run build-wasm`, `bun run build/ci`,
and the release build regenerate the parsers before compiling them.
`bun run test` runs:
- the corpus in `test/corpus`, with the native build and with the Wasm build (the first run downloads the WASI SDK);
- a check that the real-world C++ files in `examples/`, the checked-in ones and those of the cloned repositories,
fail to parse exactly as listed in `script/known-failures.txt`. The first run clones the repositories. The example
repositories are pinned to commits in `script/parse-examples`. After a grammar change or a moved pin alters that
list, `script/parse-examples` rewrites it; review its diff before committing;
- a performance check (`test/unit/performance.test.ts`) that recovering from an error on each line takes linear
time, since consumers parse files while they are being edited. It loads the Wasm build through
@willbooster/web-tree-sitter, which `bun run build/ci` rebuilds after regenerating the parser;
- a check (`test/unit/expressionKeywordParameter.test.ts`) that every keyword that can start an expression but not a
parameter is expected in parameter lists, so that `long(n)(sizeof(b));` stays an initialization, and that the
keyword-led arguments that make `Foo* p(nullptr);` a variable start only with such keywords or `this`, which starts
a parameter only when a declaration follows it;
- a check (`test/unit/grammarPackage.test.ts`) that `tree-sitter.json` is published in the npm package and the crate,
that the scanner headers are published in the crate, and that the vendored scanner headers match the installed
@willbooster/tree-sitter-c. After updating that dependency, run `script/copy-c-scanner`.
Only the headers listed in `script/copy-c-scanner` are verbatim copies from that package; their generator paths
refer to the C repository. `src/cppTrivia.h` and `src/initializerConditional.h` are maintained here.
Review the C scanner dispatch and external-token order against `src/scanner.c` when updating the dependency;
- a check (`test/unit/runtimeVersion.test.ts`) that `@willbooster/web-tree-sitter` in `package.json` and
`willbooster-tree-sitter` in `Cargo.lock` are the same version, since the Wasm tests run on the former and the Rust
tests, the fuzzer, and the CLI on the latter;
- checks that the Wasm build parses in Chromium (`test/unit/browser/`) and in Cloudflare Workers with and without
Node.js compatibility (`test/unit/workers.test.ts`). Run `bun run test/ci-setup` once to install Chromium.
CI also runs these tests on Linux arm64 and macOS, where the parser and scanner are compiled natively against each
platform's C library, and fuzzes the parser with libFuzzer and sanitizers (`.github/workflows/robustness.yml`).
### References
- [Hyperlinked C++ BNF Grammar](http://www.nongnu.org/hcb/)
- [EBNF Syntax: C++](http://www.externsoft.ch/download/cpp-iso.html)