bpo-42500: Fix recursion in or after except (GH-23568)

* Use counter, rather boolean state when handling soft overflows.

1 files changed, 11 insertions, 9 deletions

diff --git a/Python/ceval.c b/Python/ceval.c
index 693852e..9de9257 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -857,20 +857,22 @@ _Py_CheckRecursiveCall(PyThreadState *tstate, const char *where)
         return -1;
     }
 #endif
-    if (tstate->overflowed) {
+    if (tstate->recursion_headroom) {
         if (tstate->recursion_depth > recursion_limit + 50) {
             /* Overflowing while handling an overflow. Give up. */
             Py_FatalError("Cannot recover from stack overflow.");
         }
-        return 0;
     }
-    if (tstate->recursion_depth > recursion_limit) {
-        --tstate->recursion_depth;
-        tstate->overflowed = 1;
-        _PyErr_Format(tstate, PyExc_RecursionError,
-                      "maximum recursion depth exceeded%s",
-                      where);
-        return -1;
+    else {
+        if (tstate->recursion_depth > recursion_limit) {
+            tstate->recursion_headroom++;
+            _PyErr_Format(tstate, PyExc_RecursionError,
+                        "maximum recursion depth exceeded%s",
+                        where);
+            tstate->recursion_headroom--;
+            --tstate->recursion_depth;
+            return -1;
+        }
     }
     return 0;
 }