'__close' method may be called again in case of error

An error in a closing method may be caused by a lack of resources,
such as memory or stack space, and the error may free enough resources
(by unwinding the stack) to allow the method to work if called again.

If the closing method is already running after some error (including
its own), it is not called again.

1 files changed, 12 insertions, 10 deletions

diff --git a/lfunc.c b/lfunc.c
index 68d0632a..cd85cc1f 100644
--- a/lfunc.c
+++ b/lfunc.c
@@ -133,7 +133,8 @@ static int prepclosingmethod (lua_State *L, TValue *obj, TValue *err) {
 ** the 'level' of the upvalue being closed, as everything after
 ** that won't be used again.
 */
-static int callclosemth (lua_State *L, TValue *uv, StkId level, int status) {
+static int callclosemth (lua_State *L, StkId level, int status) {
+  TValue *uv = s2v(level);  /* value being closed */
   if (likely(status == LUA_OK)) {
     if (prepclosingmethod(L, uv, &G(L)->nilvalue))  /* something to call? */
       callclose(L, NULL);  /* call closing method */
@@ -145,9 +146,10 @@ static int callclosemth (lua_State *L, TValue *uv, StkId level, int status) {
     }
   }
   else {  /* must close the object in protected mode */
-    ptrdiff_t oldtop = savestack(L, level + 1);
-    /* save error message and set stack top to 'level + 1' */
-    luaD_seterrorobj(L, status, level);
+    ptrdiff_t oldtop;
+    level++;  /* space for error message */
+    oldtop = savestack(L, level + 1);  /* top will be after that */
+    luaD_seterrorobj(L, status, level);  /* set error message */
     if (prepclosingmethod(L, uv, s2v(level))) {  /* something to call? */
       int newstatus = luaD_pcall(L, callclose, NULL, oldtop, 0);
       if (newstatus != LUA_OK && status == CLOSEPROTECT)  /* first error? */
@@ -203,18 +205,18 @@ int luaF_close (lua_State *L, StkId level, int status) {
     StkId upl = uplevel(uv);
     TValue *slot = &uv->u.value;  /* new position for value */
     lua_assert(upl < L->top);
+    if (uv->tt == LUA_TUPVALTBC && status != NOCLOSINGMETH) {
+      /* must run closing method */
+      ptrdiff_t levelrel = savestack(L, level);
+      status = callclosemth(L, upl, status);  /* may change the stack */
+      level = restorestack(L, levelrel);
+    }
     luaF_unlinkupval(uv);
     setobj(L, slot, uv->v);  /* move value to upvalue slot */
     uv->v = slot;  /* now current value lives here */
     if (!iswhite(uv))
       gray2black(uv);  /* closed upvalues cannot be gray */
     luaC_barrier(L, uv, slot);
-    if (uv->tt == LUA_TUPVALTBC && status != NOCLOSINGMETH) {
-      /* must run closing method */
-      ptrdiff_t levelrel = savestack(L, level);
-      status = callclosemth(L, uv->v, upl, status);  /* may change the stack */
-      level = restorestack(L, levelrel);
-    }
   }
   return status;
 }