Bug: new metatable in weak table can fool the GC

All-weak tables are not being revisited after being visited during
propagation; if it gets a new metatable after that, the new metatable
may not be marked.

1 files changed, 6 insertions, 2 deletions

diff --git a/lgc.c b/lgc.c
index 5817f9ee..c01660ab 100644
--- a/lgc.c
+++ b/lgc.c
@@ -553,8 +553,12 @@ static lu_mem traversetable (global_State *g, Table *h) {
       traverseweakvalue(g, h);
     else if (!weakvalue)  /* strong values? */
       traverseephemeron(g, h, 0);
-    else  /* all weak */
-      linkgclist(h, g->allweak);  /* nothing to traverse now */
+    else {  /* all weak */
+      if (g->gcstate == GCSpropagate)
+        linkgclist(h, g->grayagain);  /* must visit again its metatable */
+      else
+        linkgclist(h, g->allweak);  /* must clear collected entries */
+    }
   }
   else  /* not weak */
     traversestrongtable(g, h);