12.1 Compiling and Linking C Extensions

A dynamic extension is a shared library (a.k.a. DLL) that extends Racket using the C API. An extension can be loaded explicitly via load-extension, or it can be loaded implicitly through require or load/use-compiled in place of a source file when the extension is located at

(build-path "compiled" "native" (system-library-subpath)

(path-add-suffix file (system-type 'so-suffix)))

relative to file.

For information on writing extensions, see Inside: Racket C API.

raco ctool is provided by the "cext-lib" package.

Three raco ctool modes help for building extensions:

• --cc : Runs the host system’s C compiler, automatically supplying flags to locate the Racket header files and to compile for inclusion in a shared library.

• --ld : Runs the host system’s C linker, automatically supplying flags to locate and link to the Racket libraries and to generate a shared library.

• --xform : Transforms C code that is written without explicit GC-cooperation hooks to cooperate with Racket’s 3m garbage collector; see Overview (BC) in Inside: Racket C API.

Compilation and linking build on the dynext/compile and dynext/link libraries. The following raco ctool flags correspond to setting or accessing parameters for those libraries: --tool, --compiler, --ccf, --ccf, --ccf-clear, --ccf-show, --linker, ++ldf, --ldf, --ldf-clear, --ldf-show, ++ldl, --ldl-show, ++cppf, ++cppf ++cppf-clear, and --cppf-show.

The --3m flag specifies that the extension is to be loaded into the 3m variant of Racket. The --cgc flag specifies that the extension is to be used with the CGC. The default depends on raco: --3m if raco itself is running in 3m, --cgc if raco itself is running in CGC.

12.1.1 API for 3m Transformation

The arguments are as for compile-extension; in addition keep-lines? can be #t to generate GCC-style annotations to connect the generated C code with the original source locations.

The file generated by xform can be compiled via compile-extension.