Re: LUA fails to parse expression with big and nested lists.

[Andrey Dobrovolsky <ken@...>]

Hi,
I want to propose much better solution of the big nested lists parsing 
problem.
The circumstances causing register pool exhaustion may be described as 
the list part followed by the next level constructor. The solution may 
be very simple and efficient - constructor as the list element must 
force storing of already processed list items. Such solution is easy and 
discards all the limitations on the nesting depth but "C stack overflow".
The patch for lua-5.4.6 attached.

Original
 readelf -s liblua.a | grep constructor
    59: 000032b0   670 FUNC    LOCAL  DEFAULT    7 constructor

Patched
readelf -s liblua.a | grep constructor
    59: 000032b0   715 FUNC    LOCAL  DEFAULT    7 constructor

Best regards!

Andrey Dobrovolsky

--- lparser.c.orig	2023-05-02 23:02:30.000000000 +0300
+++ lparser.c	2023-10-06 23:44:27.488798829 +0300
@@ -865,11 +865,11 @@
 }
 
 
-static void closelistfield (FuncState *fs, ConsControl *cc) {
+static void closelistfield (FuncState *fs, ConsControl *cc, int flush) {
   if (cc->v.k == VVOID) return;  /* there is no list item */
   luaK_exp2nextreg(fs, &cc->v);
   cc->v.k = VVOID;
-  if (cc->tostore == LFIELDS_PER_FLUSH) {
+  if ((cc->tostore == LFIELDS_PER_FLUSH) || flush){
     luaK_setlist(fs, cc->t->u.info, cc->na, cc->tostore);  /* flush */
     cc->na += cc->tostore;
     cc->tostore = 0;  /* no more items pending */
@@ -939,7 +939,7 @@
   do {
     lua_assert(cc.v.k == VVOID || cc.tostore > 0);
     if (ls->t.token == '}') break;
-    closelistfield(fs, &cc);
+    closelistfield(fs, &cc, ls->t.token == '{');
     field(ls, &cc);
   } while (testnext(ls, ',') || testnext(ls, ';'));
   check_match(ls, '}', '{', line);