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

• 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.

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"
                                  who
                                  (lisp-implementation-type)
                                  (lisp-implementation-version)
                                  os))))
         (user [:Environment %UserName]))
    [delegate Invoke user]))

(hello)

;; ==>

;; 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

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

(ql:quickload :bike)

Alternatively, you can drop the contents of the repository 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!

Do not use this if you pass Lisp callbacks to .Net code - this may cause deadlocks.

SBCL is the main development and testing platform.

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

However, there is one important issue here. That is the NullReferenceException.

Although rare in production code, this would probably lead to SBCL runtime corruption and crash, should one occur on a lisp thread.

The reason for this is described in my (D.I.) SBCL patch that had been applied recently.

Basically, on x86-64 Windows, SBCL uses VEH, and its handler catches all the exceptions before .Net Core handlers even have a chance to look at their ones. This, next, leads to a situation where SBCL disallows .Net runtime to enter into correct state, which leads to the corruption of both runtimes and process crash.

The above patch fixed the situation for usual exceptions (Exception, IndexOutOfBoundsExcepion, etc), but the EXCEPTION_ACCESS_VIOLATION(which .Net translates into NullReferenceException should the address be small enough) handler remains here. It is not clear what we should do with that situation. Maybe add another if statement, which would exclude low address space, but the best thing we can do is actually rewrite SBCL handlers on x64 Windows to use RtlInstallFunctionTableCallback instead of VEH.

Early SBCL versions(namely pre 1.5.4.13-b656602a3) 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.

• 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. Fix SBCL crashes on Windows with NullReferenceException.

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

• Write compiler macros for API and type resolution

• etc.