Handle overwriting Object::ENV in spawn

Instead of looking for Object::ENV (which can be overwritten),
directly look for the envtbl variable.  As that is static in hash.c,
and the lookup code is in process.c, add a couple non-static
functions that will return envtbl (or envtbl#to_hash).

Fixes [Bug #18164]

1 files changed, 12 insertions, 0 deletions

diff --git a/test/ruby/test_process.rb b/test/ruby/test_process.rb
index 80d2eefca9..07aa58418b 100644
--- a/test/ruby/test_process.rb
+++ b/test/ruby/test_process.rb
@@ -261,6 +261,18 @@ class TestProcess < Test::Unit::TestCase
     }
   end
 
+  def test_overwrite_ENV
+    assert_separately([],"#{<<~"begin;"}\n#{<<~"end;"}")
+    BUG = "[ruby-core:105223] [Bug #18164]"
+    begin;
+      $VERBOSE = nil
+      ENV = {}
+      pid = spawn({}, *#{TRUECOMMAND.inspect})
+      ENV.replace({})
+      assert_kind_of(Integer, pid, BUG)
+    end;
+  end
+
   MANDATORY_ENVS = %w[RUBYLIB MJIT_SEARCH_BUILD_DIR]
   case RbConfig::CONFIG['target_os']
   when /linux/