Issue #21311 has been updated by byroot (Jean Boussier). Trying to run benchmarks with `RUBY_NAMESPACE=1` crashes during init: ``` opt/rubies/head-namespaces/bin/ruby: [BUG] Segmentation fault at 0x0000000000000008 ruby 3.5.0dev (2025-05-11T00:30:16Z namespace-on-read-.. 6629795fff) +PRISM [arm64-darwin24] -- Crash Report log information -------------------------------------------- See Crash Report log file in one of the following locations: * ~/Library/Logs/DiagnosticReports * /Library/Logs/DiagnosticReports for more details. Don't forget to include the above Crash Report log file in bug reports. -- Control frame information ----------------------------------------------- c:0001 p:0000 s:0003 E:000380 DUMMY [FINISH] -- Threading information --------------------------------------------------- Total ractor count: 1 Ruby thread count for this ractor: 1 -- Machine register context ------------------------------------------------ x0: 0x0000000000000000 x1: 0x0000000000000f9f x2: 0x000000016b156668 x3: 0x0000000000000000 x4: 0x0000000000000005 x5: 0x00000000de600168 x6: 0x0000000000002ce0 x7: 0x0000000000000001 x18: 0x0000000000000000 x19: 0x0000000120026a40 x20: 0x0000000000000000 x21: 0x0000000000000f9f x22: 0x00000001051be000 x23: 0x00000001051c3668 x24: 0x0000000142e05900 x25: 0x0000000000000008 x26: 0x00000001051c3638 x27: 0x000000016b1574c0 x28: 0x0000000000000009 lr: 0x0000000104d7d420 fp: 0x000000016b156650 sp: 0x000000016b1565f0 -- C level backtrace information ------------------------------------------- /opt/rubies/head-namespaces/bin/ruby(rb_vm_bugreport+0xb6c) [0x104f315f8] /opt/rubies/head-namespaces/bin/ruby(rb_bug_for_fatal_signal+0x100) [0x104d5efd4] /opt/rubies/head-namespaces/bin/ruby(sigsegv+0x84) [0x104e897e8] /usr/lib/system/libsystem_platform.dylib(_sigtramp+0x38) [0x18de56de4] /opt/rubies/head-namespaces/bin/ruby(object_id+0x80) [0x104d7d420] /opt/rubies/head-namespaces/bin/ruby(object_id+0x80) [0x104d7d420] /opt/rubies/head-namespaces/bin/ruby(rb_initialize_main_namespace+0xe4) [0x104ddaa20] /opt/rubies/head-namespaces/bin/ruby(ruby_opt_init+0x120) [0x104e7f524] /opt/rubies/head-namespaces/bin/ruby(ruby_process_options+0x1370) [0x104e7e31c] /opt/rubies/head-namespaces/bin/ruby(ruby_options+0xb0) [0x104d69844] /opt/rubies/head-namespaces/bin/ruby(main+0x64) [0x104ca8d54] ``` ---------------------------------------- Feature #21311: Namespace on read (revised) https://bugs.ruby-lang.org/issues/21311#change-113119 * Author: tagomoris (Satoshi Tagomori) * Status: Open ---------------------------------------- This replaces #19744 ## Concept This proposes a new feature to define virtual top-level namespaces in Ruby. Those namespaces can require/load libraries (either .rb or native extension) separately from other namespaces. Dependencies of required/loaded libraries are also required/loaded in the namespace. This feature will be disabled by default at first, and will be enabled by an env variable `RUBY_NAMESPACE=1` as an experimental feature. (It could be enabled by default in the future possibly.) ### "on read" approach The "on write" approach here is the design to define namespaces on the loaded side. For example, Java packages are defined in the .java files and it is required to separate namespaces from each other. It can be implemented very easily, but it requires all libraries to be updated with the package declaration. (In my opinion, it's almost impossible in the Ruby ecosystem.) The "on read" approach is to create namespaces and then require/load applications and libraries in them. Programmers can control namespace separation at the "read" time. So, we can introduce the namespace separation incrementally. ## Motivation The "namespace on read" can solve the 2 problems below, and can make a path to solve another problem: * Avoiding name conflicts between libraries * Applications can require two different libraries safely which use the same module name. * Avoiding unexpected globally shared modules/objects * Applications can make an independent/unshared module instance. * Multiple versions of gems can be required * Application developers will have fewer version conflicts between gem dependencies if rubygems/bundler will support the namespace on read. (Support from RubyGems/Bundler and/or other packaging systems will be needed) For the motivation details, see [Feature #19744]. ## How we can use Namespace ```ruby # app1.rb PORT = 2048 class App def self.port = ::PORT def val = PORT.to_s end p App.port # 2048 # app2.rb class Number def double = self * 2 end PORT = 2048.double class App def self.port = ::PORT def val = PORT.double.to_s end p App.port # 4096 # main.rb - executed as `ruby main.rb` ns1 = Namespace.new ns1.require('./app1') # 2048 ns2 = Namespace.new ns2.require('./app2') # 4096 PORT = 8080 class App def self.port = ::PORT def val = PORT.to_s end p App.port # 8080 p App.new.val # "8080" p ns1::App.port # 2048 p ns1::App.new.val # "2048" p ns2::App.port # 4096 p ns2::App.new.val # "8192" 1.double # NoMethodError ``` ## Namespace specification ### Types of namespaces There are two namespace types, "root" and "user" namespace. "Root" namespace exists solely in a Ruby process, and "user" namespaces can be created as many as Ruby programmers want. ### Root namespace Root namespace is a unique namespace to be defined when a Ruby process starts. It only contains built-in classes/modules/constants, which are available without any `require` calls, including RubyGems itself (when `--disable-gems` is not specified). At here, "builtin" classes/modules are classes/modules accessible when users' script evaluation starts, without any require/load calls. ### User namespace User namespace is a namespace to run users' Ruby scripts. The "main" namespace is the namespace to run the user's `.rb` script specified by the `ruby` command-line argument. Other user namespaces ("optional" namespaces) can be created by `Namespace.new` call. In user namespace (both main and optional namespaces), built-in class/module definitions are copied from the root namespace, and other new classes/modules are defined in the namespace, separately from other (root/user) namespaces. The newly defined classes/modules are top-level classes/modules in the main namespace like `App`, but in optional namespaces, classes/modules are defined under the namespace (subclass of Module), like `ns::App`. In that namespace `ns`, `ns::App` is accessible as `App` (or `::App`). There is no way to access `App` in the main namespace from the code in the different namespace `ns`. ### Constants, class variables and global variables Constants, Class variables of built-in classes and global variables are also separated by namespace. Values set to class/global variables in a namespace are invisible in other namespaces. ### Methods and procs Methods defined in a namespace run with the defined namespace, even when called from other namespaces. Procs created in a namespace run with the defined namespace too. ### Dynamic link libraries Dynamic link libraries (typically .so files) are also loaded in namespaces as well as .rb files. ### Open class (Changes on built-in classes) In user namespaces, built-in class definitions can be modified. But those operations are processed as copy-on-write of class definition from the root namespace, and the changed definitions are visible only in the (user) namespace. Definitions in the root namespace are not modifiable from other namespaces. Methods defined in the root namespace run only with root-namespace definitions. ## Enabling Namespace Specify `RUBY_NAMESPACE=1` environment variable when starting Ruby processes. `1` is the only valid value here. Namespace feature can be enabled only when Ruby processes start. Setting `RUBY_NAMESPACE=1` after starting Ruby scripts performs nothing. ## Pull-request https://github.com/ruby/ruby/pull/13226 -- https://bugs.ruby-lang.org/