Macro lucet_runtime::lucet_hostcalls

macro_rules! lucet_hostcalls {
    {
    $
    ($ (# [$ attr : meta]) * pub unsafe extern "C" fn $ name : ident
     (& mut $ vmctx : ident $ (, $ arg : ident : $ arg_ty : ty) *,) -> $
     ret_ty : ty { $ ($ body : tt) * }) *
} => { ... };
}

Deprecated since 0.5.0:

Use the #[lucet_hostcall] attribute instead

The macro that surrounds definitions of Lucet hostcalls in Rust.

Note: this macro has been deprecated and replaced by the #[lucet_hostcall] attribute.

It is important to use this macro for hostcalls, rather than exporting them directly, as it installs unwind protection that prevents panics from unwinding into the guest stack.

Since this is not a proc macro, the syntax is unfortunately fairly brittle. The functions it encloses must be of the form:

#[$attr1]
#[$attr2]
... // any number of attributes are supported; in most cases you will want `#[no_mangle]`
pub unsafe extern "C" fn $name( // must be `pub unsafe extern "C"`
    &mut $vmctx,
    $arg1: $arg1_ty,
    $arg2: $arg2_ty,
    ... , // trailing comma must always be present
) -> $ret_ty { // return type must always be present even if it is `()`
    // body
}