From 07671cbfd7654bc357c30fab9ba46ded9faa101c Mon Sep 17 00:00:00 2001
From: Dave Lucia <dave@dave-mac-mini.tail23398.ts.net>
Date: Tue, 10 Feb 2026 20:00:12 -0800
Subject: [PATCH 1/2] feat: Add _G global table

Implements _G as a table containing references to global functions.

Features:
- _G exists and is a table
- _G contains standard library functions
- _G._G references itself

Limitations (marked as skipped tests):
- Not a live reference (changes don't sync with globals)
- Full live reference would require metamethods or VM changes

Tests: 3 passing, 2 skipped
All existing tests pass (1089 tests, 0 failures)
---
 lib/lua/vm/stdlib.ex | 20 +++++++++++++++++++
 test/lua_test.exs    | 46 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 66 insertions(+)

diff --git a/lib/lua/vm/stdlib.ex b/lib/lua/vm/stdlib.ex
index a322df5..15ac7f2 100644
--- a/lib/lua/vm/stdlib.ex
+++ b/lib/lua/vm/stdlib.ex
@@ -37,6 +37,26 @@ defmodule Lua.VM.Stdlib do
     |> Lua.VM.Stdlib.String.install()
     |> Lua.VM.Stdlib.Math.install()
     |> Lua.VM.Stdlib.Table.install()
+    |> install_global_g()
+  end
+
+  # Install _G global table - a table that references the global environment
+  defp install_global_g(state) do
+    # Create a table containing all current globals
+    # Copy all globals into the _G table
+    g_data = state.globals
+
+    {{:tref, _id} = g_ref, state} = State.alloc_table(state, g_data)
+
+    # Set _G to point to this table
+    state = State.set_global(state, "_G", g_ref)
+
+    # Also add _G to itself so _G._G == _G
+    state = State.update_table(state, g_ref, fn table ->
+      %{table | data: Map.put(table.data, "_G", g_ref)}
+    end)
+
+    state
   end
 
   # type(v) — returns the type of v as a string
diff --git a/test/lua_test.exs b/test/lua_test.exs
index 2a29e9c..9cbec95 100644
--- a/test/lua_test.exs
+++ b/test/lua_test.exs
@@ -1397,6 +1397,52 @@ defmodule LuaTest do
     end
   end
 
+  describe "_G global table" do
+    setup do
+      %{lua: Lua.new(sandboxed: [])}
+    end
+
+    test "_G references the global environment", %{lua: lua} do
+      # _G should be a table that contains itself
+      assert {[true], _} = Lua.eval!(lua, "return _G ~= nil")
+      assert {[true], _} = Lua.eval!(lua, "return type(_G) == 'table'")
+    end
+
+    test "_G contains global functions", %{lua: lua} do
+      # Standard functions should be accessible via _G
+      assert {[true], _} = Lua.eval!(lua, "return _G.print == print")
+      assert {[true], _} = Lua.eval!(lua, "return _G.type == type")
+      assert {[true], _} = Lua.eval!(lua, "return _G.tostring == tostring")
+    end
+
+    test "_G contains itself", %{lua: lua} do
+      # _G._G should reference _G
+      assert {[true], _} = Lua.eval!(lua, "return _G._G == _G")
+    end
+
+    @tag :skip
+    test "can set globals via _G", %{lua: lua} do
+      # Requires _G to be a live reference with __index/__newindex metamethods
+      code = """
+      _G.myvar = 42
+      return myvar
+      """
+
+      assert {[42], _} = Lua.eval!(lua, code)
+    end
+
+    @tag :skip
+    test "can read globals via _G", %{lua: lua} do
+      # Requires _G to be a live reference with __index metamethods
+      code = """
+      myvar = 123
+      return _G.myvar
+      """
+
+      assert {[123], _} = Lua.eval!(lua, code)
+    end
+  end
+
   defp test_file(name) do
     Path.join(["test", "fixtures", name])
   end

From 731e23519844a45611cd66a6b69b1e5b0443f865 Mon Sep 17 00:00:00 2001
From: Dave Lucia <dave@dave-mac-mini.tail23398.ts.net>
Date: Tue, 10 Feb 2026 20:23:06 -0800
Subject: [PATCH 2/2] format: Fix formatting in stdlib.ex

---
 lib/lua/vm/stdlib.ex | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/lib/lua/vm/stdlib.ex b/lib/lua/vm/stdlib.ex
index 15ac7f2..5d9e663 100644
--- a/lib/lua/vm/stdlib.ex
+++ b/lib/lua/vm/stdlib.ex
@@ -52,9 +52,10 @@ defmodule Lua.VM.Stdlib do
     state = State.set_global(state, "_G", g_ref)
 
     # Also add _G to itself so _G._G == _G
-    state = State.update_table(state, g_ref, fn table ->
-      %{table | data: Map.put(table.data, "_G", g_ref)}
-    end)
+    state =
+      State.update_table(state, g_ref, fn table ->
+        %{table | data: Map.put(table.data, "_G", g_ref)}
+      end)
 
     state
   end