From: Brandt Bucher <brandtbucher@microsoft.com>
Date: Wed, 26 Mar 2025 19:00:16 +0000 (-0700)
Subject: GH-119866: Don't clear frame->stackpointer on release builds (GH-131750)
X-Git-Tag: v3.14.0a7~178
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=4b3d5b604210f68005ef64d5346ca169385f5acf;p=thirdparty%2FPython%2Fcpython.git

GH-119866: Don't clear frame->stackpointer on release builds (GH-131750)
---

diff --git a/Include/internal/pycore_interpframe.h b/Include/internal/pycore_interpframe.h
index 097da4edee1a..1d373d55ab2d 100644
--- a/Include/internal/pycore_interpframe.h
+++ b/Include/internal/pycore_interpframe.h
@@ -163,15 +163,17 @@ _PyFrame_GetLocalsArray(_PyInterpreterFrame *frame)
     return frame->localsplus;
 }
 
-/* Fetches the stack pointer, and sets stackpointer to NULL.
-   Having stackpointer == NULL ensures that invalid
-   values are not visible to the cycle GC. */
+// Fetches the stack pointer, and (on debug builds) sets stackpointer to NULL.
+// Having stackpointer == NULL makes it easier to catch missing stack pointer
+// spills/restores (which could expose invalid values to the GC) using asserts.
 static inline _PyStackRef*
 _PyFrame_GetStackPointer(_PyInterpreterFrame *frame)
 {
     assert(frame->stackpointer != NULL);
     _PyStackRef *sp = frame->stackpointer;
+#ifndef NDEBUG
     frame->stackpointer = NULL;
+#endif
     return sp;
 }