#lang scribble/doc
@(require scribble/manual
          "common.ss")

@title[#:tag "ext"]{Compiling to Native Code via C}

The @DFlag{extension}/@Flag{e} mode for @|mzc| is similar to the
@DFlag{zo} mode, except that the compiled form of the module is a
native-code shared library instead of bytecode. Native code is
generated with the help of the host system's C compiler. This mode is
rarely useful, because the just-in-time (JIT) compiler that is built
into PLT Scheme provides better performance with lower overhead on the
platforms where it is supported (see @secref[#:doc '(lib
"scribblings/guide/guide.scrbl") "performance"]).

As with @DFlag{zo} mode, the generated shared library by default is
placed in the same directory as the source file---which is not where
it will be found automatically when loading the source. Use the
@as-index{@DFlag{auto-dir}} flag to redirect the output to a
@scheme[(build-path "compiled" "native" (system-library-subpath))]
subdirectory, where it will be found automatically when loading the
source file.

The @DFlag{--c-source}/@Flag{c} mode for @|mzc| is like the
@DFlag{extension}/@Flag{e} mode, except that compilation stops with
the generation of C code.

All of the C compiler and linker flags that apply to @DFlag{cc} and
@DFlag{ld} mode also apply to @DFlag{extension} mode; see
@secref["cc"].  In addition, a few flag provide some control over the
Scheme-to-C compiler: @as-index{@DFlag{no-prop}},
@as-index{@DFlag{inline}}, @as-index{@DFlag{no-prim}},
@as-index{@DFlag{stupid}},
@as-index{@DFlag{unsafe-disable-interrupts}},
@as-index{@DFlag{unsafe-skip-tests}}, and
@as-index{@DFlag{unsafe-fixnum-arithmetic}}. Use @exec{mzc --help} for
an explanation of each flag.