Skip to content


Switch branches/tags

Name already in use

A tag already exists with the provided branch name. Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. Are you sure you want to create this branch?

Latest commit



Failed to load latest commit information.
Latest commit message
Commit time


MoarVM (short for Metamodel On A Runtime Virtual Machine) is a runtime built for the 6model object system. It is primarily aimed at running NQP and Rakudo, but should be able to serve as a backend for any compilers built using the NQP compiler toolchain.

Get It

Either download it from the MoarVM site or clone it from GitHub:

git clone

If you use the automatically generated release tarballs or zip files please note that they don't contain the third party libraries needed to successfully build MoarVM.

Build It

Build Status

Building and installing the VM itself takes just:

make install

(Or nmake/gmake on Windows). Currently it is known to build on Windows with MSVC and gcc, and with gcc and clang on Linux & MacOS X. We're expanding this with time.

Type perl --help to see the configure-time options, as well as some descriptions of the make-time options/targets.

Building an NQP with MoarVM

After installing MoarVM, you can clone the NQP repository or grab a source tarball and use the script in it like so:

perl --backend=moar --prefix=where_your_moarvm_install_lives

Alternatively, the same script in NQP is able to clone, build and install a copy of MoarVM on its own if you supply the --gen-moar flag.

Please bear in mind that this will be the prefix to the /bin, /lib and other directories where the moar executable and other files are going to be installed, so you'll have to use /usr if you want moar to be copied to /usr/bin.

Building a Rakudo with MoarVM

When pointing the script in rakudo's repository at a --prefix that has an nqp-m installed in it, it will automatically detect and configure the MoarVM backend. Alternatively, --backend=moar,jvm can be used to force it to build the MoarVM and JVM backends, for example. Just like in the NQP script, you have the option to supply a --gen-moar flag that will do all the work for you, including creating an nqp-m.


MoarVM is currently in development. It can run all of the NQP test suite, all of the Rakudo sanity tests, and passes more spectests than any other Rakudo backend.

Unlike the JVM or JS backend of NQP, the MoarVM repo is not integrated into the NQP source repo but instead can be pulled in by running --gen-moar configure script in the NQP repo.

Feature overview

Some key features provided by MoarVM include:

  • Meta-object programming, using the 6model design
  • Precise, generational, and parallel GC
  • Unicode 13.1 support (Unicode Character Database, encodings, normalization)
  • First-class code objects, lexical variables and closures
  • Exceptions
  • Continuations
  • Bounded serialization
  • Runtime loading of code
  • Big integers
  • A range of IO and process support, including asynchronous sockets, signals, timers, and processes
  • Native calling and native pointer manipulation
  • Threads, mutexes, condition variables, semaphores, and blocking queues
  • Bytecode specialization by type, and numerous optimizations (including resolution of method calls and multiple dispatch, dead code elimination, inlining, on stack replacement, scalar replacement, and partial escape analysis)
  • JIT compilation
  • Instrumentation-based profiling of call frames and allocations
  • Heap snapshotting
  • Remote Debugging with single stepping and variable/object introspection


Contributions by pull request are accepted. Commit bits are given to those who contribute quality work. If you are interested in contributing, drop by the #moarvm channel on

See the LICENSE file in the root directory for information on the license of the source code in the MoarVM repository.


Linker can't find appropriate symbols on macOS

If MoarVM fails to build, and the error looks something like this:

ld: symbol(s) not found for architecture x86_64

you likely have an incompatible mix of build and bin utils.

While it is common to have toolchains installed from third party repositories in macOS, they aren't all compatible. In the event you run into this issue, please try these steps.

  1. Unlink your tools in homebrew: brew unlink binutils
  2. Destroy and re-clone MoarVM or rakudobrew
  3. Attempt the build again from scratch

If you want to use a GNU toolchain, and you get an error telling you to see this file, simply supply the --toolchain=gnu flag and this package will configure and build with a GNU toolchain.

Please note: If you use mixed Xcode and non-Xcode tools, you are likely to run into trouble. As such, this configuration is unsupported.

You need different code for gcc versus clang

Note both compilers define macro __GNUC__, so macro __clang__ needs to be tested first to disambiguate the two.