From d5779161cdf247c6a6daac1e5944cb0ba09a239b Mon Sep 17 00:00:00 2001
From: Kim Alvefur <zash@zash.se>
Date: Wed, 28 Jul 2021 20:37:57 +0200
Subject: [PATCH 1/2] Add function to mark values to skip

This is more explicit, hopefully easier to understand. Can also be
overridden as I intend to do next.
---
 dump.lua | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/dump.lua b/dump.lua
index 9ac864a..34cc785 100644
--- a/dump.lua
+++ b/dump.lua
@@ -109,6 +109,9 @@ local function dump_state(file, options)
 		processed[obj] = processed_counter;
 		return processed_counter;
 	end
+	local function skip(obj)
+		processed[obj] = 0;
+	end
 
 	local escapes = {
 		["\""] = "\\\"", ["\\"] = "\\\\", ["\b"] = "\\b",
@@ -159,8 +162,8 @@ local function dump_state(file, options)
 		thread_mt = debug.getmetatable(debug.getregistry()[1]);
 	};
 
-	processed[dump_state] = 0;
-	processed[root] = 0;
+	skip(dump_state);
+	skip(root);
 
 	push(root);
 

From 43831102e5ba24c02f6b542b9e2eea5976329070 Mon Sep 17 00:00:00 2001
From: Kim Alvefur <zash@zash.se>
Date: Wed, 28 Jul 2021 20:40:06 +0200
Subject: [PATCH 2/2] Use memory location for ids on Lua 5.4+

Pointers are more stable and will have the same value across
invocations, unlike the counter method which may assign different ids to
the same object on each run.

Having stable IDs makes it easier to compare dumps from different times.
---
 dump.lua | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/dump.lua b/dump.lua
index 34cc785..77066b0 100644
--- a/dump.lua
+++ b/dump.lua
@@ -113,6 +113,34 @@ local function dump_state(file, options)
 		processed[obj] = 0;
 	end
 
+	if pcall(string.format, "%p", "") then
+		local format = string.format;
+		local function new_id(obj)
+			local t = type(obj);
+			if t == "function" or t == "string" or t == "table" or t == "userdata" or t == "thread" then
+				return format("%s:%p", t, obj);
+			elseif t == "number" or t == "boolean" or t == "nil" then
+				return format("%s:%q", t, obj);
+			else
+				error("don't know how to reference a "..t)
+			end
+		end
+
+		function skip(obj)
+			processed[ new_id(obj) ] = 0;
+		end
+
+		function get_id(obj) --> string | 0
+			if nil == obj then return 0; end
+			local id = new_id(obj);
+			if not processed[id] then
+				push(obj);
+				processed[id] = 0;
+			end
+			return id;
+		end
+	end
+
 	local escapes = {
 		["\""] = "\\\"", ["\\"] = "\\\\", ["\b"] = "\\b",
 		["\f"] = "\\f", ["\n"] = "\\n", ["\r"] = "\\r", ["\t"] = "\\t"};