HTTP/2 200 x-amz-id-2: atzmPRmRgs5NkCnZU+VyVykWYKS4nIcewNN0tDAPaMTwtOgo13vB41JI6P+ZQxGvX1BqimPnmz4= x-amz-request-id: PM3P7VMAGFS37AQ3 last-modified: Thu, 22 May 2025 20:41:09 GMT etag: "4ed545184fdb8592900941632fa8cc07" x-amz-server-side-encryption: AES256 server: AmazonS3 content-encoding: gzip via: 1.1 varnish, 1.1 varnish content-type: text/plain; charset=utf-8 accept-ranges: bytes age: 0 date: Sat, 26 Jul 2025 20:00:24 GMT x-served-by: cache-tyo11920-TYO, cache-bom-vanm7210069-BOM x-cache: MISS, MISS x-cache-hits: 0, 0 x-timer: S1753560024.794580,VS0,VE323 vary: Accept-Encoding content-length: 1285 From: "jhawthorn (John Hawthorn) via ruby-core" Date: 2025-05-22T20:34:43+00:00 Subject: [ruby-core:122238] [Ruby Bug#21362] Namespace: Inline method caches poisoned with builtins Issue #21362 has been reported by jhawthorn (John Hawthorn). ---------------------------------------- Bug #21362: Namespace: Inline method caches poisoned with builtins https://bugs.ruby-lang.org/issues/21362 * Author: jhawthorn (John Hawthorn) * Status: Open * Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN ---------------------------------------- ``` ruby File.write("/tmp/ntest.rb", <<~'RUBY') class Integer def succ = self + 2 end module Test def self.run = 10.times.to_a end RUBY module Test def self.run = 10.times.to_a end ns = Namespace.new ns.require("/tmp/ntest.rb") p namespaced: ns::Test.run p main: Test.run ``` ``` RUBY_NAMESPACE=1 ruby test_namespace_succ.rb ruby: warning: Namespace is experimental, and the behavior may change in the future! See doc/namespace.md for known issues, etc. {namespaced: [0, 2, 4, 6, 8]} {main: [0, 2, 4, 6, 8]} ``` What's happening here is that we have a number of "builtin" Ruby files which are loaded during the VM boot. The instruction sequences and method definitions from these files end up as part of the "root" namespace. However this iseq can still include inline caches, and in this example we see the cache poisoned by being run in a namespace with succ redefined. I was surprised by this, I expected it to call using the "root" namespace. It's definitely a strange edge-case to redefine `succ`, but the namespace semantics here are important because how this is defined impacts how useful builtins can be: - If builtins inherit their namespace from the caller, then they cannot use inline caches (or inline caches must always check for namespace validity) and also cannot be JIT compiled (unless the JIT also checks for namespace validity, and given the complexity of rb_current_namespace, it would be very undesirable). This is very bad as converting C code to builtin Ruby has been important for getting better performance. - If builtins make calls using the "root" namespace, inline caching and the JIT should work (actually there may be advantages to both since the namespace is mostly immutable). However this will limit what we are able to move from C to Ruby, as it wouldn't be possible to have the same semantics as C methods (where the caller's namespace is used). -- https://bugs.ruby-lang.org/ ______________________________________________ ruby-core mailing list -- ruby-core@ml.ruby-lang.org To unsubscribe send an email to ruby-core-leave@ml.ruby-lang.org ruby-core info -- https://ml.ruby-lang.org/mailman3/lists/ruby-core.ml.ruby-lang.org/