mirror of
https://github.com/idris-lang/Idris2.git
synced 2024-12-17 08:11:45 +03:00
104 lines
3.3 KiB
ReStructuredText
104 lines
3.3 KiB
ReStructuredText
*************************
|
|
C with Reference Counting
|
|
*************************
|
|
|
|
There is an experimental code generator which compiles to an executable via C,
|
|
using a reference counting garbage collector. This is intended as a lightweight
|
|
(i.e. minimal dependencies) code generator that can be ported to multiple
|
|
platforms, especially those with memory constraints.
|
|
|
|
Performance is not as good as the Scheme based code generators, partly because
|
|
the reference counting has not yet had any optimisation, and partly because of
|
|
the limitations of C. However, the main goal is portability: the generated
|
|
code should run on any platform that supports a C compiler.
|
|
|
|
This code generator can be accessed via the REPL command:
|
|
|
|
::
|
|
|
|
Main> :set cg refc
|
|
|
|
Alternatively, you can set it via the ``IDRIS2_CG`` environment variable:
|
|
|
|
::
|
|
|
|
$ export IDRIS2_CG=refc
|
|
|
|
The C compiler it invokes is determined by either the ``IDRIS2_CC`` or ``CC``
|
|
environment variables. If neither is set, it uses ``cc``.
|
|
|
|
This code generator does not yet support `:exec`, just `:c`.
|
|
|
|
Also note that, if you link with any dynamic libraries for interfacing with
|
|
C, you will need to arrange for them to be accessible via ``LD_LIBRARY_PATH``
|
|
when running the executable. The default Idris 2 support libraries are
|
|
statically linked.
|
|
|
|
Extending RefC
|
|
==============
|
|
|
|
RefC can be extended to produce a new backend for languages that support C
|
|
foreign functions. For example, a
|
|
`Python backend for Idris <https://github.com/madman-bob/idris2-python>`_.
|
|
|
|
In your backend, use the ``Compiler.RefC`` functions ``generateCSourceFile``,
|
|
``compileCObjectFile {asLibrary = True}``, and
|
|
``compileCFile {asShared = True}`` to generate a ``.so`` shared object file.
|
|
|
|
.. code-block:: idris
|
|
|
|
_ <- generateCSourceFile defs cSourceFile
|
|
_ <- compileCObjectFile {asLibrary = True} cSourceFile cObjectFile
|
|
_ <- compileCFile {asShared = True} cObjectFile cSharedObjectFile
|
|
|
|
To run a compiled Idris program, call the ``int main(int argc, char *argv[])``
|
|
function in the compiled ``.so`` file, with the arguments you wish to pass to
|
|
the running program.
|
|
|
|
For example, in Python:
|
|
|
|
.. code-block:: python
|
|
|
|
import ctypes
|
|
import sys
|
|
|
|
argc = len(sys.argv)
|
|
argv = (ctypes.c_char_p * argc)(*map(str.encode, sys.argv))
|
|
|
|
cdll = ctypes.CDLL("main.so")
|
|
cdll.main(argc, argv)
|
|
|
|
Extending RefC FFIs
|
|
-------------------
|
|
|
|
To make the generated C code recognize additional FFI languages beyond the
|
|
standard RefC FFIs, pass the ``additionalFFILangs`` option to
|
|
``generateCSourceFile``, with a list of the language identifiers your backend
|
|
recognizes.
|
|
|
|
.. code-block:: idris
|
|
|
|
_ <- generateCSourceFile {additionalFFILangs = ["python"]} defs cSourceFile
|
|
|
|
This will generate stub FFI function pointers in the generated C file, which
|
|
your backend should set to the appropriate C functions before ``main`` is
|
|
called.
|
|
|
|
Each ``%foreign "lang: funcName, opts"`` definition will produce a stub whose
|
|
name is given by ``cName (UN $ lang ++ "_" ++ funcName)``, of the appropriate
|
|
function pointer type.
|
|
|
|
So the ``%foreign`` function
|
|
|
|
.. code-block:: idris
|
|
|
|
%foreign "python: abs"
|
|
abs : Int -> Int
|
|
|
|
produces a stub ``python_abs``, which can be backpatched in Python by:
|
|
|
|
.. code-block:: python
|
|
|
|
abs_ptr = ctypes.CFUNCTYPE(ctypes.c_int64, ctypes.c_int64)(abs)
|
|
ctypes.c_void_p.in_dll(cdll, "python_abs").value = ctypes.cast(abs_ptr, ctypes.c_void_p).value
|