Optimized

• Comparisons (eq, <, etc.) are optimized out based on type information.

Version 3.0.1 (LLVM15-20, 22) 2026-06-24

Fixed

• Fixes the archive tarball which was broken for 3.0.0. Thanks @fosskers for noticing.
• Archive mechanism now properly uses the pinned commits rather than git branches.
• Bad warning call in Khazern #1803.

Version 3.0.0 (LLVM15-20, 22) 2026-06-18

Added

• Support for LLVM20 and LLVM22. LLVM21 is excluded due to API incompatibility.
• Weak-value and weak-key-and-value hash tables, as well as an interface for weak-key-or-value tables, although at present they are actually strong tables in practice.
• ext:macroexpand-all macroexpands a form and its subforms.
• Arguments to bytecode functions are made available to debuggers.
• ext:deoptimize can temporarily replace almost all native-compiled functions with a simpler bytecode version with better debuggability. ext:reoptimize restores the native version.
• A style warning is signaled if the compiler assumes a symbol names a function and then sees it defined as a macro.
• New interfaces for reading and evaluating code with tracked source locations: ext:with-source-tracking, ext:stream-source-location, ext:read-source, ext:augment-source, ext:eval-source, ext:compile-source.

Changed

• Use Khazern extended for CL:LOOP
• :output-type parameter to compile-file is replaced by :native. :native t will build a fasl with both bytecode and native versions of code. If :native is not provided, it defaults to cmp:*compile-file-native*.
• compile can similarly be set to compile natively or to leave functions as bytecode with the cmp:*compile-native* variable.
• Build modes are changed: :faso, :bytecode-faso, :fasoll, :fasobc, :fasl build modes are removed. Only :bytecode and the new :native can be used. :default-native is a new build flag that can be used to control whether the built Clasp will native-compile files and functions by default (i.e. it controls the default values of cmp:*compile-file-native* and cmp:*compile-native*.
• The build procedure is completely rewritten, building Clasp's Lisp code using another Lisp implementation instead of boostrapping from the C++ Clasp.

Fixed

• Weak pointers and weak hash tables survive snapshot save/load.
• ext:quit can be used from any thread, not just the initial thread.
• Quasiquoted vectors are read correctly (#1666).
• The bytecode compiler detects malformed bindings.
• Literal arrays with fill pointers are not dumped with excess elements.
• setf of apply no longer has multiple evaluation problems.
• Improve error messages for package name conflicts. Fixes #1722.
• FASL loading is more resilient in the face of heavy file use and interruptions. Thanks @dg1sbg.
• Writing non-base-chars into base strings by various means (e.g. replace) now signals an error instead of treating the low byte of the codepoint as a base char.
• ext:macroexpand-all no longer allows macros to expand into tagbody tags.

Removed

• -z/--snapshot-symbols-save command line option, occasionally used for snapshot debugging. You can call core:mangled-symbol-names if the effect is still needed.
• FASO and other compile-file output types, other than FASL. compile-file now always produces a FASL.

Optimized

• FASL loading batches reads more, improving load times. Thanks @dg1sbg.
• Array copying operations like subseq and replace cons less.

Version 2.7.0 (LLVM15-19) 2025-01-21

Added

• Package lock support, based on SBCL's. Currently ignores local bindings. Thanks @bumblingbats.
• Add support for 80-bit and 128-bit LONG-FLOAT. Extended precision LONG-FLOAT is available on amd64 and non-Apple arm64 platforms. It is automatically detected and enabled.
• LLVM19 support.
• Interrupts have now been organized into a coherent interface. Clasp will signal conditions of type MP:INTERRUPT at opportune times, and these conditions can be handled like any others.
• Extensions to Clasp and CANDO can now be built against an installed Clasp implementation and dynamically loaded. For an example see clasp-hello-world.

Changed

• Floating point exceptions FE_INVALID, FE_OVERFLOW and FE_DIVBYZERO now signal the corresponding lisp errors by default.

Fixed

• Pathnames and filesystem operations support Unicode (#1595).
• Package names support Unicode (#1596).
• Clasp threads can now be more reliably interrupted while they are blocking (e.g. waiting to grab a mutex, or for input).

Version 2.6.0 (LLVM15-18) 2024-06-03

Added

• LLVM18 support.

Changed

• Exit with error code when unknown option is present on command line.
• EVAL now uses bytecode, improving evaluation speed.
• Bytecode is now simpler for functions with &rest parameters, as well as functions that close over arguments.

Fixed

• Avoid inserting fill newlines after newline format directive in logical block format directive.
• Don't buffer overrun when encoding UCS-4 streams.
• The bytecode system can properly handle functions with more than 255 keyword parameters.
• Bytecode FASLs can contain multidimensional arrays specialized to sub-byte integer types.
• Avoid a double free when translating const char* arguments in the C++ bridge.
• macroexpand does not ignore shadowing function bindings (#1556).
• BTB compiler can handle closure variables deleted by optimization.
• (setf elt) calls (setf sequence:elt) properly on extended sequences.
• BTB compiler handles non-constant load-time-values.
• When set-macro-character is given a non-function, it signals an error without breaking the readtable.

Optimized

• Single dispatch generic functions don't perform redundant argument count checks.

Version 2.5.0 (LLVM15-17) 2024-01-01

Added

• New module named "gray-streams" which makes it possible to initialize the Gray stream protocol without calls to internal functions.
• New build mode :bytecode-faso which builds the kernel as native code (FASO) while the bytecode compiler is active.
• Generic gray:stream-file-length which implements cl:file-length for Gray streams.
• Generic versions of cl:pathname and cl:truename, both of which are available after the Gray stream modules is required.
• Generic (setf gray:stream-element-type), gray:stream-external-format, and (setf gray:stream-external-format) for basic support of bivalent streams.
• Generic gray:stream-file-string-length which implements cl:file-string-length for Gray streams.
• The bytecode compiler warns about unused variables.

Changed

• cl:format and pprint now respect the value returned by gray:stream-line-length.
• cl:close now uses the :abort argument to decide what to do with the resulting file. If :abort is non-NIL and the file was created as a result of :if-does-not-exist :create then the file is deleted. If :abort is non-NIL, there was an existing file and :if-exists is either :supersede or :rename-and-delete then the original file is restored.

Removed

• Obsolete :object, :ll, :bc, and :fasl build modes.

Fixed

• cl:read-line so it correctly returns lines that end with EOF.
• cl:read-byte so it respects the eof-error-p and eof-value arguments for Gray streams.

Version 2.4.0 (LLVM15-17) 2023-10-01

Added

• Bytecode stores source location info for debugging.
• Bytecode stores variable info, so that variables can be viewed in the debugger.
• The bytecode compiler tracks source positions for error reporting.
• Circle detection for load forms in bytecode FASL.
• Bytecode functions can be compiled directly into native code with cl:compile (experimental).
• Cross-reference (xref) capability: Search for callers of a given function with ext:who-calls, and etc. Only works for bytecode right now.
• Support for Linux AARCH64.
• LLVM17 support. LLVM15 and LLVM16 are still supported.

Changed

• Improved printing of backquote and unquote.

Fixed

• Avoid segmentation faults from incorrectly calling MP:PROCESS-JOIN in EXT:RUN-PROGRAM.

Version 2.3.0 (LLVM15-16) 2023-06-04

Added

• Bytecode compiled images via build mode :bytecode.
• FASL magic number sniffing for CL:LOAD. This enables FASL files to be loaded even if the filename extension is incorrect.
• Preliminary Apple Silicon support. Must be compiled with bytecode either by specifying --build-mode=bytecode when invoking koga or by adding :build-mode :bytecode to the config.sexp file.
• LLVM16 support. LLVM15 is still supported.

Changed

• Updated to Eclector v0.9.0

Fixed

• Use Eclector state protocol to enable readtable changes during compiling. Fixes #1398.

Version 2.2.0 (LLVM15) 2023-03-01

Added

• ext:describe-compiler-policy to get information about the current behavior of the compiler.
• gray:stream-line-length Gray stream extension method.
• Support for building Clasp using CCL and ECL versus the default implementation of SBCL.
• Export of ext:num-logical-processors to return CPU count.

Changed

• Updated to LLVM 15 and CLANG 15.

Fixes

• Ensure that print-unreadable-object can accept output stream designators.
• Set stream column to zero after printing the prompt in a REPL. Fixes #1348.
• Return correct values for listen when applied to file streams. This is done by checking for available bytes using read when poll/select indicate the next read will not block. Otherwise use non-blocking read. Fixes #1404.
• Prevent format parameters from appearing after colon or at sign modifiers.
• Avoid putting NIL into simple LOOP when compiling format directives.

Optimizations

• Arithmetic comparisons between floats and fixnums no longer cons.

Version 2.1.0 (LLVM14) 2023-01-01

Added

• Add ext:list-all-logical-hosts and ext:logical-host-p functions to query the current logical host status.
• Operators for profiling CLOS code: clos:with-profiling

Changed

• Removed stage and image format command line options (-t and -T) and replaced with options to specify image or snapshot file (--image or --snapshot) and --base option for loading base image when extensions are present.
• print-unreadable-object now prints qualified symbols for the :type t option and uses pprint-logical-block when pretty printing.

Fixes

• ext:run-program works with string streams.
• print-object is now invoked for all calls to write.
• slot-unbound is called for unbound condition slots (#1390).
• Multiple inheritance of class-allocated slots is resolved breadth-first (#1392).

Version 2.0.0 (LLVM14) 2022-10-26

This release is dedicated to Dr. Karsten Poeck, who died after a short illness in July of 2022. Karsten made many significant contributions to Clasp, including reviving and solidifying our test frameworks. We are saddened by his sudden passing, and will miss the insightful conversations with him.

Added

• Lisp based koga metabuilder that outputs Ninja build files.
• basic Debian packaging files.
• core:*extension-systems*, core:*initialize-hooks* and core:*terminate-hooks dynamic variables have been added to support new extension loading method. core:*extension-systems* is a list of keywords that name extension systems to load after Clasp starts and before --load and --eval command line options are processed. The remaining two variables are lists of functions that are called to do initialization before a REPL is started and termination after the REPL exits.
• --script <file> command line option which equivalent to passing --norc, --noinform and --non-interactive. Any shebang in <file> will also be skipped.
• Asynchronous external process control with ext:run-program.
• Function ext:temporary-directory that returns the directory used for temporary files.
• Function ext:printing-char-p that returns non-NIL for graphic characters that are not blank glyphs. This is an extension of the ANSI specification that defines "printing" characters as graphic characters aside from the space character.

Changed

• core:lisp-implementation-id and core:clasp-git-full-commit only return non-NIL values if Clasp was built in a git working tree.
• graphic-char-p, alpha-char-p, alphanumericp, upper-case-p, lower-case-p, both-case-p, char-upcase and char-downcase now no longer depend on C++ locale functions and are now generated directly from the Unicode character tables.
• Loading of extensions such as Cando no longer uses startup scripts via LOAD. Instead the systems associated with each extension are loaded via QL:QUICKLOAD or as a fallback ASDF:LOAD-SYSTEM.
• Behavior of --rc command line option has changed. Relative paths passed via this option are no longer assumed to be located in the user's home directory.
• The logical hosts used by Clasp to locate source code and other components of Clasp has been changed. Only the reserved logical host SYS is now used. The default mappings for a system installed to /usr/ are
  1. SYS:LIB;**;*.*.* ↦ /usr/lib/clasp/**/*.*
  2. SYS:GENERATED;**;*.*.* ↦ /usr/share/clasp/generated/**/*.*
  3. SYS:EXECUTABLE;**;*.*.* ↦ /usr/bin/**/*.*
  4. SYS:QUICKLISP;**;*.*.* ↦ ~/quicklisp/**/*.*
  5. SYS:**;*.*.* ↦ /usr/share/clasp/**/*.*
• ASDF systems that are loaded as part the cclasp image are now marked as immutable thereby preventing ASDF from overwriting them. These systems include the systems acclimation, alexandria, clasp-cleavir, cleavir-ast-to-bir, cleavir-ast, cleavir-ast-transformations, cleavir-attributes, cleavir-bir, cleavir-bir-transformations, cleavir-compilation-policy, cleavir-conditions, cleavir-cst-to-ast, cleavir-ctype, cleavir-environment, cleavir-io,cleavir-meter, cleavir-primop, cleavir-set, cleavir-stealth-mixins, closer-mop, concrete-syntax-tree, concrete-syntax-tree-base, concrete-syntax-tree-destructuring, concrete-syntax-tree-lambda-list, eclector, and eclector-concrete-syntax-tree.
• Source code file references for Lisp and C/C++ files compiled as part of the Clasp binary or images are now stored using logical pathnames.
• Unicode character database updated to 2022-08-03.

Removed

• core:*extensions-startup-loads* and core:*extensions-startup-evals* dynamic variables have been removed since they are no longer used.
• The --resources-dir command line option has been removed. Equivalent behavior is achieved with the CLASP_HOME environment variable.

Enhancements

• make-instance and CLOS slot access functions can be used with structure objects.
• The stepper, accessible through step, now has basic functionality.
• gctools:save-lisp-and-die now accepts a key :executable which can be used to create an executable binary with the snapshot embedded in the binary.
• garbage-collect, finalize, and save-lisp-and-die are now exported from the ext interface package.

Optimizations

• Arguments to and return values from local functions (e.g. from FLET) are passed unboxed in some common cases.
• Nonlocal exits are much faster in most cases, the exception being when the exit goes through uncooperative C++ code.
• Types inferred for many standard functions are tighter.
• Calls to some local functions with &rest parameters are more efficient.
• LENGTH is now a "vaslistable" function; &rest parameters that are only used for vaslistable functions can be compiled to avoid consing.
• Multiple value calls and APPLY calls to known functions can sometimes be optimized.
• Some MAKE-ARRAY calls are compiled more efficiently.
• Unused calls to many more (side-effect-free) standard functions are deleted.
• Accesses to 1D simple arrays of known element type are a bit faster.
• A virtual machine has been defined and implemented, greatly increasing the speed of evaluation of code that doesn't usually need to be optimized (for example, compile-time evaluations).
• The building process has been streamlined by replacing several of the bootstrapping components with the virtual machine.
• Discriminating functions now execute faster.
• The compiler now performs inlining much faster.

Fixes

• Replace hard coded paths to nm in snapshot code with NM_BINARY macro value set by configure.
• Clasp can now be built directly from source. Resolves issue #175.
• Snapshots now parse command line options such as --noinform, --noprint, --quit, and --disable-debugger.
• Source locations for warnings from errors during constant folding now print correctly.
• Unused calls that must remain in safe code are no longer deleted.
• Prevent negative zero remainder in core__next_ftruncate. Fixes #1368.

Version 1.0.0 (LLVM13) 2022-03-26

Added

• ed hooks functionality for ed function. Accessible via *ed-functions* dynamic variable.
• Implemented save-lisp-and-die. This saves the state of a running environment for loading and fast startup later. Our most complex environment Cando starts up in ~4 seconds, which is 10x faster than the old startup that loaded libraries.
• Atomics interface for lock-free concurrent programming, in the mp: package.
• Garbage collection hooks including finalizers.
• clasp-debug interface so that IDEs like SLIME can retrieve backtraces and more to present during debugging.

Enhancements

• New compiled library format called FASP - it uses concatenated object files.
• Specialized arrays for sub-byte integer types (int2, int4, etc.)
• Source tracking: Code locations are associated with source locations via DWARF, to aid in debugging and project navigation.
• Fully integrated the customizable reader ECLECTOR

Fixes

• Fixed many errors identified by the ansi-test-suite ANSI

Version 0.5.0

• Full integration of the Cleavir/SICL compiler by Robert Strandh
• A nascent type inference system within Cleavir by Alex Wood
• LLVM whole program, Link-Time-Optimization
• Multi threading compatible with Bordeaux threads
• Unicode, 32bit wide characters
• Specialized arrays for many primitive types (int8, int16, int32, int64, double, float)
• CFFI (C Foreign Function Interface)
• New build system based on waf (https://github.com/waf-project/waf)
• Code and file cleanup
• Better Emacs and Slime support including jumping to source (C++ and CL), tab-completion and lambda-list display
• Many, many improvements and bug fixes

Version 0.4.0

• Clasp has a completely new compiler! The Cleavir Common Lisp compiler developed by Robert Strandh as part of his SICL project. Cleavir is an advanced compiler that generates fast code and is an excellent compiler for testing advanced optimization algorithms. Cleavir carries out escape analysis to properly assign variables to the stack/heap and it does aggressive inlining. The best code that Cleavir generates has clocked within a factor of four of the speed of C. For more details see SICL
• Fixnum, character and single-float types are now immediate values and fixnums are tagged using #b000 in the bottom three bits to allow fast integer arithmetic.
• General object pointers are tagged, cons cells have a separate tag to accelerate are tagged.
• Building Clasp has been accelerated and now takes about 2.5 hours on a reasonably powerful Linux system and 3.5 hours on OS X.
• Clbind library allows programmers to expose external C++ libraries to Clasp Common Lisp.
• The build system has been improved and externals-clasp has been eliminated as a requirement.
• Clasp version 0.4.0 is a Boehm only version of Clasp. The Memory Pool System garbage collector is being tuned for Clasp and is planned to be in the 0.5.0 release.

Version 0.11

• Added ASDF support. This is still alpha. Compile the ASDF module using (core:compile-asdf). After that you can load the module using (load "sys:kernel;asdf;build;asdf.bundle"). It takes between 15-30 seconds to load (this is why I'm integrating Cleavir).
• Added :CLASP to *features* and removed :ECL from *features*. Clasp will continue to mimic the underlying ECL functionality so that Common Lisp code that supports ECL can be made to support Clasp by converting #+ecl to #+(or ecl clasp) and #-ecl to #-(or ecl clasp)
• Added code to generate object files directly from Clasp. The LLVM bitcode compiler "llc" no longer needs to be in the PATH for Clasp to generate object files from Common Lisp source. The "ld" linker does need to be accessible.