[GR-19302] Reset the Kernel#rand seed for pre-initialized contexts.

PullRequest: truffleruby/1159

Author: eregon

spec/ruby/core/kernel/rand_spec.rb

@@ -138,6 +138,16 @@
     rand(KernelSpecs::CustomRangeFloat.new(1.0)..KernelSpecs::CustomRangeFloat.new(42.0)).should be_an_instance_of(KernelSpecs::CustomRangeFloat)
     rand(Time.now..Time.now).should be_an_instance_of(Time)
   end
+
+  it "is random on boot" do
+    results = 2.times.map {
+      out = ruby_exe('p rand', options: '--disable-gems')
+      Float(out)
+    }
+    results.size.should == 2
+    # this is technically flaky, but very unlikely in a good distribution
+    results[0].should_not == results[1]
+  end
 end
 
 describe "Kernel#rand" do

spec/tags/core/kernel/rand_tags.txt

@@ -4,3 +4,4 @@ fails:Kernel.rand given an exclusive range returns a Float between the two given
 fails:Kernel.rand returns nil when range is backwards
 fails:Kernel.rand returns the range start/end when Float range is 0
 fails:Kernel.rand supports custom object types
+slow:Kernel.rand is random on boot

src/main/ruby/truffleruby/core/thread.rb

@@ -395,7 +395,9 @@ def thread_variables
   end
 end
 
-Thread.current.send :internal_thread_initialize
+Truffle::Boot.redo do
+  Thread.current.send :internal_thread_initialize
+end
 
 class ThreadGroup
   def initialize