5.5 Static Callout and Callback Cores

► |  | The Racket Foreign Interface

1 | Overview
2 | Loading Foreign Libraries
3 | C Types
4 | Pointer Functions
5 | Derived Utilities
6 | Miscellaneous Support
7 | Unexported Primitive Functions
| Bibliography
| Index

▼ | 5 | Derived Utilities

5.1 | Safe Homogenous Vectors
5.2 | Safe C Vectors
5.3 | Tagged C Pointer Types
5.4 | Serializable C Struct Types
5.5 | Static Callout and Callback Cores
5.6 | Defining Bindings
5.7 | Allocation and Finalization
5.8 | Custodian Shutdown Registration
5.9 | Atomic Execution
5.10 | Speculatively Atomic Execution
5.11 | Thread Scheduling
5.12 | Ports
5.13 | Process-Wide and Place-Wide Registration
5.14 | Operating System Threads
5.15 | Garbage Collection Callbacks
5.16 | Objective-C FFI
5.17 | Cocoa Foundation
5.18 | COM (Common Object Model)
5.19 | File Security-Guard Checks
5.20 | Windows API Helpers
5.21 | Virtual Machine Primitives

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### 5.5 Static Callout and Callback Cores🔗ℹ

(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.

> > syntax
> > (_fun fun-option ... maybe-args type-spec ... -> type-spec
> > maybe-wrapper)

Like _fun from ffi/unsafe, but triggers 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 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.

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