Add objspace/trace.rb source file

Author: andrykonchin

CHANGELOG.md

@@ -86,6 +86,7 @@ Compatibility:
 * Add `freeze` keyword argument to `Marshal.load` (#2733, @andrykonchin).
 * Add `Integer.try_convert` (#2733, @moste00, @eregon).
 * Support optional `:in` keyword argument for `Time.now` and `Time.new` (#2733, @andrykonchin).
+* Add `objspace/trace` file (#2733, @andrykonchin).
 
 Performance:
 

lib/mri/objspace/trace.rb

@@ -0,0 +1,48 @@
+# This is a simple tool to enable the object allocation tracer.
+# When you have an object of unknown provenance, you can use this
+# to investigate where the object in question is created.
+#
+# = Important notice
+#
+# This is only for debugging purpose. Do not use this in production.
+# Require'ing this file immediately starts tracing the object allocation,
+# which brings a large performance overhead.
+#
+# = Usage
+#
+# 1. Add `require "objspace/trace"` into your code (or add `-robjspace/trace` into the command line)
+# 2. `p obj` will show the allocation site of `obj`
+#
+# Note: This redefines `Kernel#p` method, but not `Object#inspect`.
+#
+# = Examples
+#
+#   1: require "objspace/trace"
+#   2:
+#   3: obj = "str"
+#   4:
+#   5: p obj  #=> "str" @ test.rb:3
+if defined?(::TruffleRuby)
+  require 'objspace'
+else
+  require 'objspace.so'
+end
+
+module Kernel
+  remove_method :p
+  define_method(:p) do |*objs|
+    objs.each do |obj|
+      file = ObjectSpace.allocation_sourcefile(obj)
+      line = ObjectSpace.allocation_sourceline(obj)
+      if file
+        puts "#{ obj.inspect } @ #{ file }:#{ line }"
+      else
+        puts obj.inspect
+      end
+    end
+  end
+end
+
+ObjectSpace.trace_object_allocations_start
+
+warn "objspace/trace is enabled"

spec/tags/library/objectspace/trace_tags.txt

@@ -1,2 +1 @@
 slow:require "objspace/trace" shows object allocation sites
-fails:require "objspace/trace" shows object allocation sites

test/mri/excludes/TestObjSpace.rb

@@ -27,5 +27,4 @@
 exclude :test_name_error_message, "needs investigation"
 exclude :test_internal_class_of_on_ast, "needs investigation"
 exclude :test_dump_singleton_class, "Expected \"{\\\"address\\\":\\\"0x186e48\\\",\\\"class\\\":\\\"0x1251c38\\\",\\\"memsize\\\":1,\\\"flags\\\":{},\\\"type\\\":\\\"OBJECT\\\",\\\"length\\\":0}\" to include \"\\\"name\\\":\\\"Object\\\"\"."
-exclude :test_objspace_trace, "<[\"objspace/trace is enabled\"]> expected but was"
 exclude :test_utf8_method_names, "{\"address\":\"0x2ce228\",\"class\":\"0x998\",\"memsize\":3,\"flags\":{},\"type\":\"STRING\",\"bytesize\":2,\"value\":\"12\",\"encoding\":\"UTF-8\"}."