From 15b2a78106f85a3f8ef2efe5683148d9dad84b33 Mon Sep 17 00:00:00 2001
From: Roberto I <roberto@inf.puc-rio.br>
Date: Thu, 15 Oct 2026 13:53:40 -0300
Subject: [PATCH] Bug: Calling coroutine.close while closing after error

A call to 'coroutine.close()' while closing the coroutine returns like
'resume', with no errors, even if the coroutine previously had stopped
due to an error.
---
 lcorolib.c           |  3 ++-
 lstate.c             | 22 ++++++++++++++++++++--
 manual/manual.of     |  3 ++-
 testes/coroutine.lua | 20 ++++++++++++++++++--
 4 files changed, 42 insertions(+), 6 deletions(-)

diff --git a/lcorolib.c b/lcorolib.c
index eb30bf4d..976ac638 100644
--- a/lcorolib.c
+++ b/lcorolib.c
@@ -78,7 +78,8 @@ static int luaB_auxwrap (lua_State *L) {
     int stat = lua_status(co);
     if (stat != LUA_OK && stat != LUA_YIELD) {  /* error in the coroutine? */
       stat = lua_closethread(co, L);  /* close its tbc variables */
-      lua_assert(stat != LUA_OK);
+      if (stat == LUA_OK)
+        return 0;  /* nothing to return */
       lua_xmove(co, L, 1);  /* move error message to the caller */
     }
     if (stat != LUA_ERRMEM &&  /* not a memory error and ... */
diff --git a/lstate.c b/lstate.c
index ada0b856..08179357 100644
--- a/lstate.c
+++ b/lstate.c
@@ -319,18 +319,36 @@ TStatus luaE_resetthread (lua_State *L, TStatus status) {
   status = luaD_closeprotected(L, 1, status);
   if (status != LUA_OK)  /* errors? */
     luaD_seterrorobj(L, status, L->stack.p + 1);
-  else
+  else  /* keep in the stack only the fake function-entry for basic ci */
     L->top.p = L->stack.p + 1;
   luaD_reallocstack(L, cast_int(L->ci->top.p - L->stack.p), 0);
   return status;
 }
 
 
+/*
+** Auxiliary function to call luaE_resetthread in protected mode.
+** That function closes all tbc variables in protected mode, so the
+** only possible "error" is when a tbc variable closes the thread being
+** closed and therefore calls 'luaD_throwbaselevel'; in that case,
+** control goes directly back to the first call to lua_closethread (not
+** to the second), to properly return it.
+*/
+static void resetthread_aux (lua_State *L, void *ud) {
+  TStatus status = *cast(TStatus*, ud);
+  status = luaE_resetthread(L, status);
+  if (status != LUA_OK)
+    luaD_throw(L, status);
+}
+
+
 LUA_API int lua_closethread (lua_State *L, lua_State *from) {
   TStatus status;
   lua_lock(L);
   L->nCcalls = (from) ? getCcalls(from) : 0;
-  status = luaE_resetthread(L, L->status);
+  status = luaD_rawrunprotected(L, resetthread_aux, &L->status);
+  /* stack has error message iff there was an error */
+  lua_assert(L->top.p == L->stack.p + (status == LUA_OK ? 1 : 2));
   if (L == from)  /* closing itself? */
     luaD_throwbaselevel(L, status);
   lua_unlock(L);
diff --git a/manual/manual.of b/manual/manual.of
index 7cdc1ce3..02882492 100644
--- a/manual/manual.of
+++ b/manual/manual.of
@@ -7048,7 +7048,8 @@ The given coroutine must be dead, suspended,
 or be the running coroutine.
 For the running coroutine,
 this function does not return.
-Instead, the resume that (re)started the coroutine returns.
+Instead, the resume that (re)started the coroutine returns
+with no error and no results.
 
 For other coroutines,
 in case of error
diff --git a/testes/coroutine.lua b/testes/coroutine.lua
index ba394e0c..953c157b 100644
--- a/testes/coroutine.lua
+++ b/testes/coroutine.lua
@@ -156,8 +156,6 @@ do
   st, msg = coroutine.close(co)
   assert(st and msg == nil)
 
-  local main = coroutine.running()
-
   -- cannot close 'main'
   local st, msg = pcall(coroutine.close, main);
   assert(not st and string.find(msg, "main"))
@@ -184,6 +182,24 @@ do
     assert(st and msg == nil)
   end
 
+
+  do
+    -- again close a coroutine while closing it, but with the
+    -- coroutine in error mode.
+
+    -- after the error, the function created by 'wrap' will close the
+    -- coroutine. The close inside 'a' overrides the original close
+    -- and finishes the coroutine with no errors.
+    local co = coroutine.wrap(function()
+        local a <close> = func2close(function()
+            coroutine.close()
+        end)
+        error("y")
+      end)
+    co()  -- no errors
+  end
+
+
   -- to-be-closed variables in coroutines
   local X