Macro gc_shadowstack::dummy_letroot

macro_rules! dummy_letroot {
    ($var_name: ident: $t: ty  = $stack: expr,$value: expr) => { ... };
    ($var_name : ident = $stack: expr,$value: expr) => { ... };
}

Create rooted value and push it to provided shadowstack instance.

NOTE: This macro does not heap allocate internally. It uses some unsafe tricks to allocate value on stack and push stack reference to shadowstack. Returned rooted value internally is Pin<&mut T>.