Squashed commit of the following:

commit 467210d
Author: Sebastian Waschik <[email protected]>
Date:   Thu Dec 14 11:49:50 2023 +0100

    Return a closure without arguments in gfind

Author: tsukinoko-kun

_glua-tests/issues.lua

@@ -491,6 +491,21 @@ function test()
 end
 test()
 
+-- issue #462
+function test()
+  local x = string.gmatch("asdf", "a")
+  assert(x() == "a", "check gmatch callback")
+
+  local expected = {
+    "a",
+    "c",
+  }
+  for i in string.gmatch("abc", "[ac]") do
+    assert(i == table.remove(expected, 1), "check gmatch inside loop")
+  end
+end
+test()
+
 -- issue #304
 function test()
 	local x ={
@@ -508,4 +523,4 @@ function test()
 	  assert(#a == i)
 	end
 end
-test()
+test()

stringlib.go

@@ -14,7 +14,7 @@ func OpenString(L *LState) int {
 	//_, ok := L.G.builtinMts[int(LTString)]
 	//if !ok {
 	mod = L.RegisterModule(StringLibName, strFuncs).(*LTable)
-	gmatch := L.NewClosure(strGmatch, L.NewFunction(strGmatchIter))
+	gmatch := L.NewFunction(strGmatch)
 	mod.RawSetString("gmatch", gmatch)
 	mod.RawSetString("gfind", gmatch)
 	mod.RawSetString("__index", mod)
@@ -299,7 +299,7 @@ type strMatchData struct {
 }
 
 func strGmatchIter(L *LState) int {
-	md := L.CheckUserData(1).Value.(*strMatchData)
+	md := L.CheckUserData(UpvalueIndex(1)).Value.(*strMatchData)
 	str := md.str
 	matches := md.matches
 	idx := md.pos
@@ -331,11 +331,11 @@ func strGmatch(L *LState) int {
 	if err != nil {
 		L.RaiseError(err.Error())
 	}
-	L.Push(L.Get(UpvalueIndex(1)))
 	ud := L.NewUserData()
 	ud.Value = &strMatchData{str, 0, mds}
-	L.Push(ud)
-	return 2
+	f := L.NewClosure(strGmatchIter, ud)
+	L.Push(f)
+	return 1
 }
 
 func strLen(L *LState) int {