Add Conda package

[kartik-s]

Closes #66.

Summary

This PR adds a Conda recipe for building a package called sbcl-librarian containing the following artifacts:

• lib/libsbcl_librarian.so
• lib/sbcl_librarian.core
• include/sbcl_librarian.h
• include/sbcl_librarian_err.h
• the sbcl_librarian Python package with wrappers for libsbcl_librarian.so

The CI workflows on all platforms are updated so that they:

1. Build SBCL + libsbcl from source
2. Build the sbcl-librarian Conda package and install it into an environment
3. Build calc.dll as a FASL-packed DLL against libsbcl_librarian.dll in that environment
4. Run the example C and Python programs against calc.dll

Artifacts

libsbcl_librarian.so

Built via the CMakeLists.txt file in lib/, which lists its sources and dependent libraries:

add_library(sbcl_librarian SHARED sbcl_librarian.c sbcl_librarian.h sbcl_librarian_err.h entry_point.c)
target_link_libraries(sbcl_librarian PUBLIC sbcl)

sbcl_librarian.c and sbcl_librarian.h are auto-generated bindings for this library as defined in generate-bindings.lisp:

(define-aggregate-library sbcl-librarian (:function-linkage "LIBSBCL_LIBRARIAN_API")
  diagnostics
  environment
  errors
  handles
  loader)

These bindings contain the functions that FASL-packed DLLs call to load themselves into the running Lisp image.

Additionally, we link in entry_point.c which defines the do_initialize_lisp function that gets called automatically by the system when libsbcl_librarian.so is loaded into a process. This function does the following:

1. Get the path to sbcl_librarian.core, which is installed in the same directory as the currently executing DLL.
2. Call SBCL's initialize_lisp function with the the above core file to initialize the Lisp runtime.
3. Wire up SBCL's lossage handler so that fatal Lisp errors are caught and handled.

sbcl_librarian.core

Built via generate-bindings.lisp. Loads SWANK, the sbcl-librarian library, sets up some signal-handling hacks, generates C and Python bindings, then saves the core.

include/sbcl_librarian.h

Generated via generate-bindings.lisp. Declares functions and values contained in libsbcl_librarian.so

sbcl_librarian_err.h

Declares fatal error handling jmp_bufs and flags, as well as the global error enum that gets returned by all wrapper functions.

Python package

Contains several modules that wrap the raw Python bindings:

• debug.py wraps functions for enabling/disabling the debugger + backtraces, memory + handle reporting, doing GC, and profiling
• errors.py matches the error enum defined in sbcl_librarian.h so that errors returned by C functions can be translated into Python exceptions
• fixtures.py has a test fixture that checks for handle leaks
• version.py reads the package version from VERSION.txt
• wrapper.py defines the LispObject class for wrapping handles with release logic, exception types corresponding to the errors enums defined in sbcl_librarian_err.h, and functions for wrapping raw binding functions with logic to deal with handles and exceptions

[jbouwman]

Approved, review comments mainly pertain to nonsubstantive documentation of platform quirks

[eliaslfox]

🚀