Experimental feature in GraalVM

TruffleRuby Additional Functionality

TruffleRuby is intended to be usable as a standard Ruby implementation that runs programs developed on other implementations, but it also provides additional functionality beyond that of other implementations.

See the Compatibility guide for compatibility with other Ruby implementations.

Detecting If You Run on TruffleRuby #

You can use the --version command-line option. TruffleRuby will report for example:

truffleruby ..., like ruby ..., GraalVM CE Native [x86_64-darwin]

In Ruby code, you can look at the standard RUBY_ENGINE constant, which will be 'truffleruby'. In C code TRUFFLERUBY is defined.

It is also possible to use feature-detection instead of looking at RUBY_ENGINE.

TruffleRuby is an integral part of GraalVM, so the version number of TruffleRuby is always the same as the version of GraalVM that contains it. If you are using TruffleRuby outside of GraalVM, such as a standard JVM, the version will be '0.0'. You can find the version number of GraalVM and TruffleRuby using the standard RUBY_ENGINE_VERSION constant.

TruffleRuby Methods and Classes #

TruffleRuby provides these non-standard methods and classes that provide additional functionality in the TruffleRuby module:

  • TruffleRuby.jit? reports if the GraalVM Compiler is available and will be used.

  • TruffleRuby.native? reports if TruffleRuby is compiled as a native executable.

  • TruffleRuby.cexts? reports if TruffleRuby has the GraalVM LLVM Runtime for C extensions available.

  • TruffleRuby.revision reports the source control revision used to build TruffleRuby as a String. Also available as RUBY_REVISION, like CRuby 2.7+.

  • TruffleRuby.full_memory_barrier ensures lack of reordering of loads or stores before the barrier with loads or stores after the barrier.

  • TruffleRuby.graalvm_home returns the GraalVM home or nil if running outside of GraalVM (e.g., TruffleRuby standalone).

  • TruffleRuby.synchronized(object) { } will run the block while holding an implicit lock per object instance.

Atomic References #

  • atomic_reference = TruffleRuby::AtomicReference.new(value=nil) creates a new atomic reference with a reference to a given object.

  • atomic_reference.get gets the value of an atomic reference, returning the value.

  • atomic_reference.set(new_value) sets the value of an atomic reference and causes a memory barrier on writes involving new_value.

  • atomic_reference.get_and_set(new_value) sets the value of an atomic reference, returns the previous value, and causes a memory barrier on writes involving new_value.

  • atomic_reference.compare_and_set(expected_value, new_value) sets the value of an atomic reference, only if it currently has the expected value, returning a boolean to say whether or not it was set, and causes a memory barrier on writes involving new_value. For numeric objects it will get the current value and then check that the current value is also a numeric and that it is equal to the expected value by calling ==, then perform an atomic compare and set.

  • AtomicReference is marshalable.

Concurrent Maps #

TruffleRuby::ConcurrentMap is a key-value data structure, like a Hash and using #hash and #eql? to compare keys and identity to compare values. Unlike Hash it is unordered. All methods on TruffleRuby::ConcurrentMap are thread-safe but should have higher concurrency than a fully syncronized implementation. It is intended to be used by gems such as concurrent-ruby - please use via this gem rather than using directly.

  • map = TruffleRuby::ConcurrentMap.new([initial_capacity: ...], [load_factor: ...])

  • map[key] = new_value

  • map[key]

  • map.compute_if_absent(key) { computed_value } if the key is not found, run the block and store the result. The block is run at most once. Returns the computed value.

  • map.compute_if_present(key) { |current_value| computed_value } if the key is found, run the block and store the result. If the block returns nil the entry for that key is removed. The block is run at most once. Returns the final value, or nil if the block returned nil.

  • map.compute(key) { |current_value| computed_value } run the block, passing the current value if there is one or nil, and store the result. If the block returns nil the entry for that key is removed. Returns the computed value.

  • map.merge_pair(key, new_value) { |existing_value| merged_value } if key is not found or is nil, store the new value, otherwise call the block and store the result, or remove the entry if the block returns nil. Returns the final value for that entry, or nil if the block returned nil.

  • map.replace_pair(key, expected_value, new_value) replace the value for key but only if the existing value for it is the same as expected_value (compared by identity). Returns if the value was replaced or not.

  • map.replace_if_exists(key, value) replace the value for key but only if it was found. Returns value if the key exists or nil.

  • map.get_and_set(key, new_value) sets the value for a key and returns the previous value.

  • map.key?(key) returns if a key is in the map.

  • map.delete(key) removes a key from the map if it exists, returning the value or nil if it did not exist.

  • map.delete_pair(key, expected_value) removes a key but only if the existing value for it is the same as expected_value (compared by identity). Returns if the key was deleted.

  • map.clear removes all entries from the map.

  • map.size gives the number of entries in the map.

  • map.get_or_default(key, default_value)

  • map.each_pair { |key, value| ... }

FFI #

TruffleRuby includes a Ruby-FFI backend. This should be transparent: you can just install the ffi gem as normal, and it will use TruffleRuby’s FFI backend. TruffleRuby also includes a default version of the FFI gem, so require "ffi" always works on TruffleRuby, even if the gem is not installed.

Polyglot Programming #

The Polyglot and Java modules provide access to the polyglot programming functionality of GraalVM. They are described in the Polyglot Programming guide.

Unsupported Additional Functionality #

You may be able to find some other modules and methods not listed here that look interesting, such as Truffle::POSIX or Truffle::FFI. Additional modules and methods not listed in this document are designed to support the implementation of TruffleRuby and should not be used. They may be modified or made not visible to user programs in the future, and you should not use them.

Extra macros, functions, and variables in TruffleRuby C extension headers beyond those provided by MRI, such as those starting with rb_tr_*, are unsupported and should not be used by any C extension.