Bug: GC checks stack space before running finalizer

If some stack does not have a minimum available space, the GC defers
calling a finalizer until the next cycle. That avoids errors while
running a finalizer that the programmer cannot control.

1 files changed, 4 insertions, 3 deletions

diff --git a/lgc.c b/lgc.c
index c01660ab..52cea240 100644
--- a/lgc.c
+++ b/lgc.c
@@ -1242,7 +1242,7 @@ static void finishgencycle (lua_State *L, global_State *g) {
   correctgraylists(g);
   checkSizes(L, g);
   g->gcstate = GCSpropagate;  /* skip restart */
-  if (!g->gcemergency)
+  if (g->tobefnz != NULL && !g->gcemergency && luaD_checkminstack(L))
     callallpendingfinalizers(L);
 }
 
@@ -1632,11 +1632,12 @@ static lu_mem singlestep (lua_State *L) {
       break;
     }
     case GCScallfin: {  /* call remaining finalizers */
-      if (g->tobefnz && !g->gcemergency) {
+      if (g->tobefnz && !g->gcemergency && luaD_checkminstack(L)) {
         g->gcstopem = 0;  /* ok collections during finalizers */
         work = runafewfinalizers(L, GCFINMAX) * GCFINALIZECOST;
       }
-      else {  /* emergency mode or no more finalizers */
+      else {  /* no more finalizers or emergency mode or no enough stack
+                 to run finalizers */
         g->gcstate = GCSpause;  /* finish collection */
         work = 0;
       }