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I've got a bike, you can ride it if you like
It's got a basket, a bell that rings
And things to make it look good
I'd give it to you if I could, but I borrowed it

-- Pink Floyd

Bike reinvents two wheels

  • First of all, it is RDNZL reborn

  • This time, on .Net Core, without a line of C++ code, and fully cross-platform

Now you have the batteries included! Which are of the size of Battersea Power Station.

Library status

Windows Linux macOS
SBCL OK Workaround ?
CCL OK* Workaround ?
ECL ECL Bug Workaround ?
Other ? ? ?

* With some exceptions

The above only applies to X86-64.

See below for known issues.

CircleCI status (.NET 8, SBCL and CCL on ubuntu-jammy)



This library implements cross-platform Common Lisp interface to .Net Core platform, using lisp compatibility layers.

(use-package :bike)

(named-readtables:in-readtable bike-syntax)

(import-assembly 'System.Runtime.InteropServices.RuntimeInformation)

(use-namespace 'System)
(use-namespace 'System.Runtime.InteropServices)

(defun hello ()
  (let* ((os [:RuntimeInformation %OSDescription])
         (delegate (new '(Action :string)
                        (lambda (who)
                          (format t "Hello ~a!~%You are running .Net Core~% inside ~a ~a~% on ~a"
         (user [:Environment %UserName]))
    [delegate Invoke user]))


;; ==>

;; Hello lovesan!
;; You are running .Net Core
;;  inside SBCL 1.5.3
;;  on Linux 4.15.0-1041-aws #43-Ubuntu SMP Thu Jun 6 13:39:11 UTC 2019

See examples and documentation for more info.


The most basic way to install the library at this moment would be to use quicklisp:

(ql:quickload :bike)

To get the latest version you can also clone the repo into ~/quicklisp/local-projects/bike directory.

The library, once loaded, searches for .Net Core runtime and for BikeInterop.dll library in several places, like in the executable directory.

In case of the library is unable to locate .Net Core in one of the predefined places, it then asks dotnet command to list available runtimes and picks up latest one.

The interop .Net library(BikeInterop.dll), should be unavailable, is being built, again, by utilizing the dotnet command.

To build the library, you would, of course, need .Net Core SDK installed. But running the code in production should only require .Net Core runtime installed and the built interop binary nearby.

The library handles image restore, by utilizing uiop. It searches for CoreCLR and interop layer again, then reloads cached types, and properly handles all the state.

Given this, you can deploy dumped images to other machines.

(defun hello () (bike:invoke 'System.Console 'WriteLine "Hello, World!"))
(setf uiop:*image-entry-point* #'hello)
(uiop:dump-image "hello.exe" :executable t)

;; ./hello.exe
;; ==> Hello, World!

Known Issues

SBCL is the main development and testing platform. CCL is also used for testing.

Task.Result and other things which block .Net code

Avoid using this if you pass Lisp callbacks to .Net code - this may cause deadlocks. You've been warned.

Foreign thread callbacks

.Net is known for extensive use of thread pools and such.

A CL implementation without proper support of foreign thread callbacks probably crashes should you pass a callback to some .NET code which would execute it on a different .Net thread.

  • SBCL has full support for foreign thread callbacks.
  • Unlike CCL, for example.
  • ECL requires foreign threads to be manually registered in the Lisp runtime. The library does this automatically.


The library works well on SBCL/Windows, runtimes and garbage collectors seem to coexist peacefully. SBCL callbacks can even be utilized by .Net System.Threading.Tasks

CCL/Windows does not handle foreign thread callbacks properly but otherwise, the library works fine on this implementation.

ECL/Win64 currently has this bug, which prevents the library from building:

Older Windows issues

There were some issues with SBCL and exceptions in the past, but those were resolved.

The reason for those issues was described in my (D.I.) SBCL patch that had been applied in 2019.

Basically, on x86-64 Windows, SBCL uses VEH, and its handler had been catching all the exceptions before .Net Core handlers even had a chance to look at their ones. This, next, sometimes led to a situation where SBCL disallowed .Net runtime to enter into the correct state, which led to the corruption of both runtimes and process crashes.

Seems like it has been resolved. This particular patch from Luís Oliveira greatly enhanced SBCL exception handling.


.NET 6+ runtime loading crashes Lisp runtime on Linux due to floating point exception


This is a major/blocking issue that the library author needs help with.

Apparently, .NET 6 changed something in its floating point exception handling on Linux, and since then, Lisp runtimes crash with SIGFPE on CoreCLR initialization.

An example of such crash:

CORRUPTION WARNING in SBCL pid 151 tid 163:
Received signal 8 @ 7f00cbeb2c3b in non-lisp tid 163, resignaling to a lisp thread.
The integrity of this image is possibly compromised.
Continuing with fingers crossed.
Floating point exception (core dumped)

The source of this FP exception seems to be some operation involving NaN, on some .Net background thread.

There's a workaround for SBCL, mentioned in the issue comments. Before loading the library, execute the following:

(sb-vm::set-floating-point-modes :traps (remove :invalid (getf (sb-vm::get-floating-point-modes) :traps)))

This would disable NaN-related exceptions for SBCL.

You can also disable all FP exceptions, if you like:

(sb-vm::set-floating-point-modes :traps nil)

However, the side effect is that you would get no floating-point-related errors whatsoever
so that for ex. (/ 1.0 0.0) would lead to a result of #.SINGLE-FLOAT-POSITIVE-INFINITY instead of a condition of type DIVISION-BY-ZERO.

For CCL:

(ccl:set-fpu-mode :invalid nil)

ECL workaround:

(ext:trap-fpe 'floating-point-invalid-operation nil)

Also, take a look at library.

You may want to wrap your application entry point function in float-features:with-float-traps-masked macro on application deployment.

Older linux issues

Early SBCL versions(namely pre were frequently crashing into LDB with a cryptic message of blockables unblocked if .Net Core runtime was present in a lisp process.

The reason for this is that SBCL and .Net Core stomp on each other signals, in a kind of a wrong way.

Seems that it is not only a case of .Net Core.

Thankfully, Stas Boukarev(stassats) implemented a workaround in the latest SBCL.

We still have to understand what may that workaround do to .Net Core runtime, but at least, it solves a problem of unavoidable and frequent crashes.

On overall, this need to be debugged out further. Maybe we would ask for help someone from .Net Core team.

UPD 2019-07-13: CoreFX(the .Net Core stdlib) also establishes signals for handling System.Diagnostics.Process classes and Console Ctrl handlers. We let it handle processes, because it can handle that perfectly(that means, including processes started by lisp, e.g. using uiop:run-program), but revert the SIGINT handler for lisp one.


Testers are welcome.


Here be dragons


  • Documentation and tests are always good

  • Add more examples which utilize third-party assemblies, NuGet, or something like that

  • dotnet command interface

  • NuGet interface

  • Fancy async/await syntax

  • MacOS X testing

  • Implement some cache for parsed type definitions

  • Expose DEFKNOW-alike API to the user

  • Investigate CoreCLR interop on Linux.

  • Optimize invocation cache (maybe write some hash functions instead of using sxhash etc)

  • Write compiler macros for API and type resolution

  • etc.