Fix frame traversal for backtraces.

1 files changed, 12 insertions, 5 deletions

diff --git a/src/lj_debug.c b/src/lj_debug.c
index be7fb2b1..09896462 100644
--- a/src/lj_debug.c
+++ b/src/lj_debug.c
@@ -71,9 +71,18 @@ static BCPos debug_framepc(lua_State *L, GCfunc *fn, cTValue *nextframe)
       /* Lua function below errfunc/gc/hook: find cframe to get the PC. */
       void *cf = cframe_raw(L->cframe);
       TValue *f = L->base-1;
-      if (cf == NULL)
-        return NO_BCPOS;
-      while (f > nextframe) {
+      for (;;) {
+        if (cf == NULL)
+          return NO_BCPOS;
+        while (cframe_nres(cf) < 0) {
+          if (f >= restorestack(L, -cframe_nres(cf)))
+            break;
+          cf = cframe_raw(cframe_prev(cf));
+          if (cf == NULL)
+            return NO_BCPOS;
+        }
+        if (f < nextframe)
+          break;
         if (frame_islua(f)) {
           f = frame_prevl(f);
         } else {
@@ -82,8 +91,6 @@ static BCPos debug_framepc(lua_State *L, GCfunc *fn, cTValue *nextframe)
           f = frame_prevd(f);
         }
       }
-      if (cframe_prev(cf))
-        cf = cframe_raw(cframe_prev(cf));
       ins = cframe_pc(cf);
     }
   }