5.5 Static Callout and Callback Cores
| (require ffi/unsafe/static) | package: base |
The
ffi/unsafe/static library provides the same bindings
as ffi/unsafe, but with a replacement _fun
form.
Added in version 8.11.0.2 of package base.
Like _fun from ffi/unsafe, but intended to trigger an
error at compile time in the CS implementation of Racket if the
compiler is unable to infer enough information about the resulting C
type to statically generate code for callouts and
callbacks using the type.
The check for static generation is currently disabled; do not use
this form until the check is restored (planned for version 8.13).
The type-spec forms and some fun-option forms within _fun are arbitrary expressions that can compute C types and options at run time. If the optimizer can statically infer underlying representations, then it can generate the necessary code for a callout or callback statically, instead of deferring code generation to run time. This optimization applies even when using _fun from ffi/unsafe, but _fun from ffi/unsafe/static insists that the optimization must apply.
Currently, the benefit of static generation for callout and callback code is limited, because run-time code generation is fast and cached. In the long run, static generation may provide more benefit.