From 4bdf9962bfd413077d979af4ddc406e7fcd4bbd6 Mon Sep 17 00:00:00 2001
From: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date: Fri, 13 Feb 2015 14:01:17 -0200
Subject: [PATCH] bug: suspended function can have its 'func' field not
 pointing to its function, crashing debug functions

---
 ldebug.c | 27 +++++++++++++++++++++++++--
 1 file changed, 25 insertions(+), 2 deletions(-)

diff --git a/ldebug.c b/ldebug.c
index 93bfc002..f6c25db3 100644
--- a/ldebug.c
+++ b/ldebug.c
@@ -1,5 +1,5 @@
 /*
-** $Id: ldebug.c,v 2.109 2014/12/10 11:30:09 roberto Exp roberto $
+** $Id: ldebug.c,v 2.110 2015/01/02 12:52:22 roberto Exp roberto $
 ** Debug Interface
 ** See Copyright Notice in lua.h
 */
@@ -48,6 +48,22 @@ static int currentline (CallInfo *ci) {
 }
 
 
+/*
+** If function yielded, its 'func' can be in the 'extra' field. The
+** next function restores 'func' to its correct value for debugging
+** purposes. (It exchanges 'func' and 'extra'; so, when called again,
+** after debugging, it also "re-restores" ** 'func' to its altered value.
+*/
+static void swapextra (lua_State *L) {
+  if (L->status == LUA_YIELD) {
+    CallInfo *ci = L->ci;  /* get function that yielded */
+    StkId temp = ci->func;  /* exchange its 'func' and 'extra' values */
+    ci->func = restorestack(L, ci->extra);
+    ci->extra = savestack(L, temp);
+  }
+}
+
+
 /*
 ** this function can be called asynchronous (e.g. during a signal)
 */
@@ -144,6 +160,7 @@ static const char *findlocal (lua_State *L, CallInfo *ci, int n,
 LUA_API const char *lua_getlocal (lua_State *L, const lua_Debug *ar, int n) {
   const char *name;
   lua_lock(L);
+  swapextra(L);
   if (ar == NULL) {  /* information about non-active function? */
     if (!isLfunction(L->top - 1))  /* not a Lua function? */
       name = NULL;
@@ -158,6 +175,7 @@ LUA_API const char *lua_getlocal (lua_State *L, const lua_Debug *ar, int n) {
       api_incr_top(L);
     }
   }
+  swapextra(L);
   lua_unlock(L);
   return name;
 }
@@ -165,12 +183,15 @@ LUA_API const char *lua_getlocal (lua_State *L, const lua_Debug *ar, int n) {
 
 LUA_API const char *lua_setlocal (lua_State *L, const lua_Debug *ar, int n) {
   StkId pos = 0;  /* to avoid warnings */
-  const char *name = findlocal(L, ar->i_ci, n, &pos);
+  const char *name;
   lua_lock(L);
+  swapextra(L);
+  name = findlocal(L, ar->i_ci, n, &pos);
   if (name) {
     setobjs2s(L, pos, L->top - 1);
     L->top--;  /* pop value */
   }
+  swapextra(L);
   lua_unlock(L);
   return name;
 }
@@ -270,6 +291,7 @@ LUA_API int lua_getinfo (lua_State *L, const char *what, lua_Debug *ar) {
   CallInfo *ci;
   StkId func;
   lua_lock(L);
+  swapextra(L);
   if (*what == '>') {
     ci = NULL;
     func = L->top - 1;
@@ -288,6 +310,7 @@ LUA_API int lua_getinfo (lua_State *L, const char *what, lua_Debug *ar) {
     setobjs2s(L, L->top, func);
     api_incr_top(L);
   }
+  swapextra(L);  /* correct before option 'L', which can raise a mem. error */
   if (strchr(what, 'L'))
     collectvalidlines(L, cl);
   lua_unlock(L);