From aa01d2568dcecf5a12ce2d8f04e969658ea46c89 Mon Sep 17 00:00:00 2001
From: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date: Fri, 30 Jun 2000 11:29:35 -0300
Subject: [PATCH] symbolic execution must handle return and tailcall

---
 ldebug.c | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/ldebug.c b/ldebug.c
index 050cc6c8..6ab85434 100644
--- a/ldebug.c
+++ b/ldebug.c
@@ -1,5 +1,5 @@
 /*
-** $Id: ldebug.c,v 1.24 2000/06/26 19:28:31 roberto Exp roberto $
+** $Id: ldebug.c,v 1.25 2000/06/28 20:20:36 roberto Exp roberto $
 ** Debug Interface
 ** See Copyright Notice in lua.h
 */
@@ -245,15 +245,27 @@ static Instruction luaG_symbexec (const Proto *pt, int lastpc, int stackpos) {
     top++;  /* `arg' */
   while (pc < lastpc) {
     const Instruction i = code[pc++];
+    LUA_ASSERT(NULL, top <= pt->maxstacksize, "wrong stack");
     switch (GET_OPCODE(i)) {
+      case OP_RETURN: {
+        LUA_ASSERT(NULL, top >= GETARG_U(i), "wrong stack");
+        top = GETARG_U(i);
+        break;
+      }
       case OP_CALL: {
         int nresults = GETARG_B(i);
         if (nresults == MULT_RET) nresults = 1;
+        LUA_ASSERT(NULL, top >= GETARG_A(i), "wrong stack");
         top = GETARG_A(i);
         while (nresults--)
           stack[top++] = pc-1;
         break;
       }
+      case OP_TAILCALL: {
+        LUA_ASSERT(NULL, top >= GETARG_A(i), "wrong stack");
+        top = GETARG_B(i);
+        break;
+      }
       case OP_PUSHNIL: {
         int n;
         for (n=0; n<GETARG_U(i); n++)
@@ -281,12 +293,12 @@ static Instruction luaG_symbexec (const Proto *pt, int lastpc, int stackpos) {
       case OP_JMPONT:
       case OP_JMPONF: {
         int newpc = pc + GETARG_S(i);
-        if (newpc >= lastpc) {
+        if (lastpc < newpc)
+          top--;  /* original code did not jump; condition was false */
+        else {
           stack[top-1] = pc-1;  /* value generated by or-and */
           pc = newpc;  /* do the jump */
         }
-        else
-          top--;  /* original code did not jump; condition was false */
         break;
       }
       case OP_PUSHNILJMP: {
@@ -302,6 +314,7 @@ static Instruction luaG_symbexec (const Proto *pt, int lastpc, int stackpos) {
         LUA_ASSERT(NULL, luaK_opproperties[GET_OPCODE(i)].push != VD,
                    "invalid opcode for default");
         top -= luaK_opproperties[GET_OPCODE(i)].pop;
+        LUA_ASSERT(NULL, top >= 0, "wrong stack");
         for (n=0; n<luaK_opproperties[GET_OPCODE(i)].push; n++)
           stack[top++] = pc-1;
       }