crabgrind 0.2.1

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# `crabgrind`

## [Valgrind Client Request](https://valgrind.org/docs/manual/manual-core-adv.html#manual-core-adv.clientreq) interface for Rust programs

[![crates.io](https://img.shields.io/crates/v/crabgrind)][crates.io]
[![libs.rs](https://img.shields.io/badge/libs.rs-crabgrind-orange)][libs.rs]
[![documentation](https://img.shields.io/docsrs/crabgrind)][documentation]
[![license](https://img.shields.io/crates/l/crabgrind)][license]

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## Summary

`crabgrind` is a small library that enables `Rust` programs to tap into
`Valgrind`'s tools and environment.

It exposes full set of [Valgrind's client requests][vg-client.req] in Rust,
manages the structure, type conversions and enforces static typing where
possible.

## Usage

**Minimum Supported Rust Version:** 1.64

First, add `crabgrind` to `Cargo.toml`

```toml
[dependencies]
crabgrind = "0.2"
```

> Note: This crate is `no_std`, dependency free and doesn't need `alloc`

### Build Configuration

We need to build against local Valgrind installation to read `C` macro
definition, constants, and supported requests.

The build script (`build.rs`) attempts to locate headers in this order:

1. **Environment Variable:** If `VALGRIND_INCLUDE` is set, it is used as the
   include path.
1. **pkg-config:** The system is queried via `pkg-config`.
1. **Standard Paths:** Using standard include paths.

If headers cannot be located, the crate compiles using dummy headers; any
request will \[`panic!`\] at runtime.

### Example

Use some of the
[Client Requests](https://docs.rs/crabgrind/latest/crabgrind/#modules):

```rust
use crabgrind::{self as cg, valgrind::RunningMode};

fn main() {
    if matches!(cg::valgrind::running_mode(), RunningMode::Native) {
        println!("Run me under Valgrind");
    } else {
        cg::println!("Hey, Valgrind!");
    }
}
```

And run under `Valgrind`

> ```bash
> :~$ cargo build
> :~$ valgrind ./target/debug/app
> ```

## Implementation

[Valgrind's client request][vg-client.req] mechanism is a `C` implementation
detail, exposed strictly via `C` macros. Since `Rust` does not support `C`
preprocessor, these macros cannot be used directly.

`crabgrind` wraps the foundational `VALGRIND_DO_CLIENT_REQUEST` macro via FFI
binding. All higher-level client requests are implemented in Rust on top of this
binding.

The overhead per request, compared to using `C` macros directly is strictly the
cost of a single function call.

The implementation is independent of any specific Valgrind version. Instead,
mismatches between requests and local Valgrind instance are handled at
compile-time in a zero-cost way for supported requests.

## Features

If you need your builds to be free of Valgrind artifacts, enable the `opt-out`
feature. This turns every request into no-op.

> ```toml
> crabgrind = { version = "0.2", features = ["opt-out"] }
> ```

## Runtime Safety

We are coupled to the Valgrind version present during compilation.

If a request is invoked at runtime that is unsupported by the active Valgrind
instance (e.g. running under an older Valgrind), the call panics immediately,
showing the version mismatch message and request requirements.

## License

`crabgrind` is distributed under `MIT` license.

`Valgrind` itself is a GPL2, however `valgrind/*.h` headers are distributed
under a BSD-style license, so we can use them without worrying about license
conflicts.

[crates.io]: https://crates.io/crates/crabgrind
[documentation]: https://docs.rs/crabgrind
[libs.rs]: https://lib.rs/crates/crabgrind
[license]: https://github.com/2dav/crabgrind/blob/main/LICENSE/MIT.LICENSE
[vg-client.req]: https://valgrind.org/docs/manual/manual-core-adv.html#manual-core-adv.clientreq