8 files changed, 118 insertions, 16 deletions

diff --git a/ldo.c b/ldo.c
index 6d0184ec..12e0364b 100644
--- a/ldo.c
+++ b/ldo.c
@@ -221,13 +221,21 @@ l_noret luaD_errerr (lua_State *L) {
 
 
 /*
-** Check whether stack has enough space to run a simple function (such
-** as a finalizer): At least BASIC_STACK_SIZE in the Lua stack and
-** 2 slots in the C stack.
+** Check whether stacks have enough space to run a simple function (such
+** as a finalizer): At least BASIC_STACK_SIZE in the Lua stack, two
+** available CallInfos, and two "slots" in the C stack.
 */
 int luaD_checkminstack (lua_State *L) {
-  return ((stacksize(L) < MAXSTACK - BASIC_STACK_SIZE) &&
-          (getCcalls(L) < LUAI_MAXCCALLS - 2));
+  if (getCcalls(L) >= LUAI_MAXCCALLS - 2)
+    return 0;  /* not enough C-stack slots */
+  if (L->ci->next == NULL && luaE_extendCI(L, 0) == NULL)
+    return 0;  /* unable to allocate first ci */
+  if (L->ci->next->next == NULL && luaE_extendCI(L, 0) == NULL)
+    return 0;  /* unable to allocate second ci */
+  if (L->stack_last.p - L->top.p >= BASIC_STACK_SIZE)
+    return 1;  /* enough (BASIC_STACK_SIZE) free slots in the Lua stack */
+  else  /* try to grow stack to a size with enough free slots */
+    return luaD_growstack(L, BASIC_STACK_SIZE, 0);
 }
 
 
@@ -616,7 +624,7 @@ void luaD_poscall (lua_State *L, CallInfo *ci, int nres) {
 
 
 
-#define next_ci(L)  (L->ci->next ? L->ci->next : luaE_extendCI(L))
+#define next_ci(L)  (L->ci->next ? L->ci->next : luaE_extendCI(L, 1))
 
 
 /*
diff --git a/lgc.c b/lgc.c
index f1d9a7ce..0f89451c 100644
--- a/lgc.c
+++ b/lgc.c
@@ -1293,7 +1293,7 @@ static void finishgencycle (lua_State *L, global_State *g) {
   correctgraylists(g);
   checkSizes(L, g);
   g->gcstate = GCSpropagate;  /* skip restart */
-  if (!g->gcemergency && luaD_checkminstack(L))
+  if (g->tobefnz != NULL && !g->gcemergency && luaD_checkminstack(L))
     callallpendingfinalizers(L);
 }
 
diff --git a/lstate.c b/lstate.c
index 70a11aae..7d341991 100644
--- a/lstate.c
+++ b/lstate.c
@@ -68,14 +68,19 @@ void luaE_setdebt (global_State *g, l_mem debt) {
 }
 
 
-CallInfo *luaE_extendCI (lua_State *L) {
+CallInfo *luaE_extendCI (lua_State *L, int err) {
   CallInfo *ci;
-  lua_assert(L->ci->next == NULL);
-  ci = luaM_new(L, CallInfo);
-  lua_assert(L->ci->next == NULL);
-  L->ci->next = ci;
+  ci = luaM_reallocvector(L, NULL, 0, 1, CallInfo);
+  if (l_unlikely(ci == NULL)) {  /* allocation failed? */
+    if (err)
+      luaM_error(L);  /* raise the error */
+    return NULL;  /* else only report it */
+  }
+  ci->next = L->ci->next;
   ci->previous = L->ci;
-  ci->next = NULL;
+  L->ci->next = ci;
+  if (ci->next)
+    ci->next->previous = ci;
   ci->u.l.trap = 0;
   L->nci++;
   return ci;
diff --git a/lstate.h b/lstate.h
index 20dc4d24..01387283 100644
--- a/lstate.h
+++ b/lstate.h
@@ -438,7 +438,7 @@ union GCUnion {
 LUAI_FUNC void luaE_setdebt (global_State *g, l_mem debt);
 LUAI_FUNC void luaE_freethread (lua_State *L, lua_State *L1);
 LUAI_FUNC lu_mem luaE_threadsize (lua_State *L);
-LUAI_FUNC CallInfo *luaE_extendCI (lua_State *L);
+LUAI_FUNC CallInfo *luaE_extendCI (lua_State *L, int err);
 LUAI_FUNC void luaE_shrinkCI (lua_State *L);
 LUAI_FUNC void luaE_checkcstack (lua_State *L);
 LUAI_FUNC void luaE_incCstack (lua_State *L);
diff --git a/ltests.c b/ltests.c
index c4905f94..ce2b20ca 100644
--- a/ltests.c
+++ b/ltests.c
@@ -1106,6 +1106,27 @@ static int stacklevel (lua_State *L) {
 }
 
 
+static int resetCI (lua_State *L) {
+  CallInfo *ci = L->ci;
+  while (ci->next != NULL) {
+    CallInfo *tofree = ci->next;
+    ci->next = ci->next->next;
+    luaM_free(L, tofree);
+    L->nci--;
+  }
+  return 0;
+}
+
+
+static int reallocstack (lua_State *L) {
+  int n = cast_int(luaL_checkinteger(L, 1));
+  lua_lock(L);
+  luaD_reallocstack(L, cast_int(L->top.p - L->stack.p) + n, 1);
+  lua_unlock(L);
+  return 0;
+}
+
+
 static int table_query (lua_State *L) {
   const Table *t;
   int i = cast_int(luaL_optinteger(L, 2, -1));
@@ -2182,6 +2203,8 @@ static const struct luaL_Reg tests_funcs[] = {
   {"s2d", s2d},
   {"sethook", sethook},
   {"stacklevel", stacklevel},
+  {"resetCI", resetCI},
+  {"reallocstack", reallocstack},
   {"sizes", get_sizes},
   {"testC", testC},
   {"makeCfunc", makeCfunc},
diff --git a/testes/gc.lua b/testes/gc.lua
index 62713dac..e50d9029 100644
--- a/testes/gc.lua
+++ b/testes/gc.lua
@@ -707,4 +707,46 @@ end
 
 collectgarbage(oldmode)
 
+
+if T then
+  print("testing stack issues when calling finalizers")
+
+  local X
+  local obj
+
+  local function initobj ()
+    X = false
+    obj = setmetatable({}, {__gc = function ()  X = true end})
+  end
+
+  local function loop (n)
+    if n > 0 then loop(n - 1) end
+  end
+
+  -- should not try to call finalizer without a CallInfo available
+  initobj()
+  loop(20)   -- ensure stack space
+  T.resetCI()   -- remove extra CallInfos
+  T.alloccount(0)   -- cannot allocate more CallInfos
+  obj = nil
+  collectgarbage()   -- will not call finalizer
+  T.alloccount()
+  assert(X == false)
+  collectgarbage()   -- now will call finalizer (it was still pending)
+  assert(X == true)
+
+  -- should not try to call finalizer without stack space available
+  initobj()
+  loop(5)     -- ensure enough CallInfos
+  T.reallocstack(0)   -- remove extra stack slots
+  T.alloccount(0)   -- cannot reallocate stack
+  obj = nil
+  collectgarbage()   -- will not call finalizer
+  T.alloccount()
+  assert(X == false)
+  collectgarbage()   -- now will call finalizer (it was still pending)
+  assert(X == true)
+end
+
+
 print('OK')
diff --git a/testes/memerr.lua b/testes/memerr.lua
index 9c940ca7..a55514a9 100644
--- a/testes/memerr.lua
+++ b/testes/memerr.lua
@@ -282,6 +282,25 @@ testamem("growing stack", function ()
   return foo(100)
 end)
 
+
+collectgarbage()
+collectgarbage()
+global io, T, setmetatable, collectgarbage, print
+
+local Count = 0
+testamem("finalizers", function ()
+  local X = false
+  local obj = setmetatable({}, {__gc = function ()  X = true end})
+  obj = nil
+  T.resetCI()   -- remove extra CallInfos
+  T.reallocstack(18)   -- remove extra stack slots
+  Count = Count + 1
+  io.stderr:write(Count, "\n")
+  T.trick(io)
+  collectgarbage()
+  return X
+end)
+
 -- }==================================================================
 
 
diff --git a/testes/tracegc.lua b/testes/tracegc.lua
index a8c929df..c1154f90 100644
--- a/testes/tracegc.lua
+++ b/testes/tracegc.lua
@@ -1,10 +1,15 @@
 -- track collections
 
+
 local M = {}
 
 -- import list
-local setmetatable, stderr, collectgarbage =
-         setmetatable, io.stderr, collectgarbage
+local stderr, collectgarbage = io.stderr, collectgarbage
+
+-- the debug version of setmetatable does not create any object (such as
+-- a '__metatable' string), and so it is more appropriate to be used in
+-- a finalizer
+local setmetatable = require"debug".setmetatable
 
 global none