mlex 0.1.3

Safe, idiomatic Rust runtime for Apple MLX: quantized LLM inference (Qwen, Gemma4, NemotronH, DharaAR, ...) with multi-modal support
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use std::cell::RefCell;
use std::ffi::{c_char, c_void, CStr};

/// Errors surfaced by the MLX runtime or by model loading.
#[derive(Debug, thiserror::Error)]
pub enum Error {
    /// An error reported by MLX itself (shape mismatch, bad dtype, ...).
    #[error("mlx: {0}")]
    Mlx(String),
    #[error("io: {0}")]
    Io(#[from] std::io::Error),
    #[error("config: {0}")]
    Config(String),
    #[error("model: {0}")]
    Model(String),
    #[error("tokenizer: {0}")]
    Tokenizer(String),
    #[error("template: {0}")]
    Template(String),
}

pub type Result<T> = std::result::Result<T, Error>;

thread_local! {
    static LAST_MLX_ERROR: RefCell<Option<String>> = const { RefCell::new(None) };
}

unsafe extern "C" fn record_error(msg: *const c_char, _data: *mut c_void) {
    let text = if msg.is_null() {
        String::from("unknown MLX error")
    } else {
        CStr::from_ptr(msg).to_string_lossy().into_owned()
    };
    LAST_MLX_ERROR.with(|slot| *slot.borrow_mut() = Some(text));
}

/// Install the process-wide MLX error handler that records errors instead of
/// aborting the process (the mlx-c default handler calls `exit(-1)`).
///
/// Called automatically the first time any MLX object is created; safe to
/// call repeatedly.
pub fn install_error_handler() {
    use std::sync::Once;
    static ONCE: Once = Once::new();
    ONCE.call_once(|| unsafe {
        crate::sys::mlx_set_error_handler(Some(record_error), std::ptr::null_mut(), None);
    });
}

/// Convert an mlx-c status code into a `Result`, attaching the recorded
/// error message when the call failed.
pub(crate) fn check(status: i32) -> Result<()> {
    if status == 0 {
        return Ok(());
    }
    let msg = LAST_MLX_ERROR
        .with(|slot| slot.borrow_mut().take())
        .unwrap_or_else(|| String::from("MLX call failed without a message"));
    Err(Error::Mlx(msg))
}