From f33cc4ddec886ea499d7d41dd60cac5ddc5687db Mon Sep 17 00:00:00 2001
From: Roberto I <roberto@inf.puc-rio.br>
Date: Wed, 26 Nov 2025 11:18:29 -0300
Subject: New conceptual model for vararg

Conceptually, all functions get their vararg arguments in a vararg
table. The storing of vararg arguments in the stack is always treated
as an optimization.
---
 ltm.c | 64 +++++++++++++++++++++++++++++++++++++++++++++++++++-------------
 1 file changed, 51 insertions(+), 13 deletions(-)

(limited to 'ltm.c')

diff --git a/ltm.c b/ltm.c
index 8d64235e..39ac59d4 100644
--- a/ltm.c
+++ b/ltm.c
@@ -242,6 +242,7 @@ static void createvarargtab (lua_State *L, StkId f, int n) {
   luaH_set(L, t, &key, &value);  /* t.n = n */
   for (i = 0; i < n; i++)
     luaH_setint(L, t, i + 1, s2v(f + i));
+  luaC_checkGC(L);
 }
 
 
@@ -265,11 +266,11 @@ void luaT_adjustvarargs (lua_State *L, CallInfo *ci, const Proto *p) {
     setobjs2s(L, L->top.p++, ci->func.p + i);
     setnilvalue(s2v(ci->func.p + i));  /* erase original parameter (for GC) */
   }
-  if (p->flag & PF_VAVAR) {  /* is there a vararg parameter? */
-    if (p->flag & PF_VATAB)  /* does it need a vararg table? */
-      createvarargtab(L, ci->func.p + nfixparams + 1, nextra);
-    else  /* no table; set parameter to nil */
-      setnilvalue(s2v(L->top.p));
+  if (p->flag & PF_VATAB)  /* does it need a vararg table? */
+    createvarargtab(L, ci->func.p + nfixparams + 1, nextra);
+  else {  /* no table; set parameter to nil */
+    setnilvalue(s2v(L->top.p));
+    L->top.p++;
   }
   ci->func.p += totalargs + 1;
   ci->top.p += totalargs + 1;
@@ -299,16 +300,53 @@ void luaT_getvararg (CallInfo *ci, StkId ra, TValue *rc) {
 }
 
 
-void luaT_getvarargs (lua_State *L, CallInfo *ci, StkId where, int wanted) {
-  int i;
-  int nextra = ci->u.l.nextraargs;
+/*
+** Get the number of extra arguments in a vararg function. If vararg
+** table has been optimized away, that number is in the call info.
+** Otherwise, get the field 'n' from the vararg table and check that it
+** has a proper value (non-negative integer not larger than the stack
+** limit).
+*/
+static int getnumargs (lua_State *L, CallInfo *ci, Table *h) {
+  if (h == NULL)  /* no vararg table? */
+    return ci->u.l.nextraargs;
+  else {
+    TValue res;
+    if (luaH_getshortstr(h, luaS_new(L, "n"), &res) != LUA_VNUMINT ||
+        l_castS2U(ivalue(&res)) > cast_uint(INT_MAX/2))
+      luaG_runerror(L, "vararg table has no proper 'n'");
+    return cast_int(ivalue(&res));
+  }
+}
+
+
+/*
+** Get 'wanted' vararg arguments and put them in 'where'. 'vatab' is
+** the register of the vararg table or -1 if there is no vararg table.
+*/
+void luaT_getvarargs (lua_State *L, CallInfo *ci, StkId where, int wanted,
+                                    int vatab) {
+  Table *h = (vatab < 0) ? NULL : hvalue(s2v(ci->func.p + vatab + 1));
+  int nargs = getnumargs(L, ci, h);  /* number of available vararg args. */
+  int i, touse;  /* 'touse' is minimum between 'wanted' and 'nargs' */
   if (wanted < 0) {
-    wanted = nextra;  /* get all extra arguments available */
-    checkstackp(L, nextra, where);  /* ensure stack space */
-    L->top.p = where + nextra;  /* next instruction will need top */
+    touse = wanted = nargs;  /* get all extra arguments available */
+    checkstackp(L, nargs, where);  /* ensure stack space */
+    L->top.p = where + nargs;  /* next instruction will need top */
+  }
+  else
+    touse = (nargs > wanted) ? wanted : nargs;
+  if (h == NULL) {  /* no vararg table? */
+    for (i = 0; i < touse; i++)  /* get vararg values from the stack */
+      setobjs2s(L, where + i, ci->func.p - nargs + i);
+  }
+  else {  /* get vararg values from vararg table */
+    for (i = 0; i < touse; i++) {
+      lu_byte tag = luaH_getint(h, i + 1, s2v(where + i));
+      if (tagisempty(tag))
+       setnilvalue(s2v(where + i));
+    }
   }
-  for (i = 0; i < wanted && i < nextra; i++)
-    setobjs2s(L, where + i, ci->func.p - nextra + i);
   for (; i < wanted; i++)   /* complete required results with nil */
     setnilvalue(s2v(where + i));
 }
-- 
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