4 files changed, 44 insertions, 8 deletions
diff --git a/Include/internal/mimalloc/mimalloc/internal.h b/Include/internal/mimalloc/mimalloc/internal.h
index 71b7ea702d6..a7daa3a40a4 100644
--- a/Include/internal/mimalloc/mimalloc/internal.h
+++ b/Include/internal/mimalloc/mimalloc/internal.h
@@ -634,10 +634,10 @@ static inline mi_block_t* mi_block_nextx( const void* null, const mi_block_t* bl
   mi_track_mem_defined(block,sizeof(mi_block_t));
   mi_block_t* next;
   #ifdef MI_ENCODE_FREELIST
-  next = (mi_block_t*)mi_ptr_decode(null, mi_atomic_load_relaxed(&block->next), keys);
+  next = (mi_block_t*)mi_ptr_decode(null, mi_atomic_load_relaxed((_Atomic(mi_encoded_t)*)&block->next), keys);
   #else
   MI_UNUSED(keys); MI_UNUSED(null);
-  next = (mi_block_t*)mi_atomic_load_relaxed(&block->next);
+  next = (mi_block_t*)mi_atomic_load_relaxed((_Atomic(mi_encoded_t)*)&block->next);
   #endif
   mi_track_mem_noaccess(block,sizeof(mi_block_t));
   return next;
diff --git a/Include/internal/pycore_ceval.h b/Include/internal/pycore_ceval.h
index 092feeb40b0..239177deb4a 100644
--- a/Include/internal/pycore_ceval.h
+++ b/Include/internal/pycore_ceval.h
@@ -353,7 +353,8 @@ PyAPI_FUNC(_PyStackRef) _PyFloat_FromDouble_ConsumeInputs(_PyStackRef left, _PyS
 extern int _PyRunRemoteDebugger(PyThreadState *tstate);
 #endif
 
-_PyStackRef _PyForIter_NextWithIndex(PyObject *seq, _PyStackRef index);
+PyAPI_FUNC(_PyStackRef)
+_PyForIter_VirtualIteratorNext(PyThreadState* tstate, struct _PyInterpreterFrame* frame, _PyStackRef iter, _PyStackRef *index_ptr);
 
 #ifdef __cplusplus
 }
diff --git a/Include/internal/pycore_magic_number.h b/Include/internal/pycore_magic_number.h
index cd1fc873623..347d9762f26 100644
--- a/Include/internal/pycore_magic_number.h
+++ b/Include/internal/pycore_magic_number.h
@@ -280,6 +280,7 @@ Known values:
     Python 3.15a0 3650 (Initial version)
     Python 3.15a1 3651 (Simplify LOAD_CONST)
     Python 3.15a1 3652 (Virtual iterators)
+    Python 3.15a1 3653 (Fix handling of opcodes that may leave operands on the stack when optimizing LOAD_FAST)
 
 
     Python 3.16 will start with 3700
@@ -293,7 +294,7 @@ PC/launcher.c must also be updated.
 
 */
 
-#define PYC_MAGIC_NUMBER 3652
+#define PYC_MAGIC_NUMBER 3653
 /* This is equivalent to converting PYC_MAGIC_NUMBER to 2 bytes
    (little-endian) and then appending b'\r\n'. */
 #define PYC_MAGIC_NUMBER_TOKEN \
diff --git a/Include/internal/pycore_stackref.h b/Include/internal/pycore_stackref.h
index f2ecc30b053..87914767252 100644
--- a/Include/internal/pycore_stackref.h
+++ b/Include/internal/pycore_stackref.h
@@ -62,14 +62,15 @@ PyAPI_FUNC(void) _Py_stackref_record_borrow(_PyStackRef ref, const char *filenam
 extern void _Py_stackref_associate(PyInterpreterState *interp, PyObject *obj, _PyStackRef ref);
 
 static const _PyStackRef PyStackRef_NULL = { .index = 0 };
+static const _PyStackRef PyStackRef_ERROR = { .index = 2 };
 
 // Use the first 3 even numbers for None, True and False.
 // Odd numbers are reserved for (tagged) integers
-#define PyStackRef_None ((_PyStackRef){ .index = 2 } )
-#define PyStackRef_False ((_PyStackRef){ .index = 4 })
-#define PyStackRef_True ((_PyStackRef){ .index = 6 })
+#define PyStackRef_None ((_PyStackRef){ .index = 4 } )
+#define PyStackRef_False ((_PyStackRef){ .index = 6 })
+#define PyStackRef_True ((_PyStackRef){ .index = 8 })
 
-#define INITIAL_STACKREF_INDEX 8
+#define INITIAL_STACKREF_INDEX 10
 
 static inline int
 PyStackRef_IsNull(_PyStackRef ref)
@@ -77,6 +78,19 @@ PyStackRef_IsNull(_PyStackRef ref)
     return ref.index == 0;
 }
 
+static inline bool
+PyStackRef_IsError(_PyStackRef ref)
+{
+    return ref.index == 2;
+}
+
+static inline bool
+PyStackRef_IsValid(_PyStackRef ref)
+{
+    /* Invalid values are ERROR and NULL */
+    return !PyStackRef_IsError(ref) && !PyStackRef_IsNull(ref);
+}
+
 static inline int
 PyStackRef_IsTrue(_PyStackRef ref)
 {
@@ -104,6 +118,7 @@ PyStackRef_IsTaggedInt(_PyStackRef ref)
 static inline PyObject *
 _PyStackRef_AsPyObjectBorrow(_PyStackRef ref, const char *filename, int linenumber)
 {
+    assert(!PyStackRef_IsError(ref));
     assert(!PyStackRef_IsTaggedInt(ref));
     _Py_stackref_record_borrow(ref, filename, linenumber);
     return _Py_stackref_get_object(ref);
@@ -155,6 +170,7 @@ _PyStackRef_CLOSE(_PyStackRef ref, const char *filename, int linenumber)
 static inline void
 _PyStackRef_XCLOSE(_PyStackRef ref, const char *filename, int linenumber)
 {
+    assert(!PyStackRef_IsError(ref));
     if (PyStackRef_IsNull(ref)) {
         return;
     }
@@ -165,6 +181,7 @@ _PyStackRef_XCLOSE(_PyStackRef ref, const char *filename, int linenumber)
 static inline _PyStackRef
 _PyStackRef_DUP(_PyStackRef ref, const char *filename, int linenumber)
 {
+    assert(!PyStackRef_IsError(ref));
     if (PyStackRef_IsTaggedInt(ref)) {
         return ref;
     }
@@ -241,9 +258,25 @@ PyStackRef_IsNullOrInt(_PyStackRef ref);
 #else
 
 #define Py_INT_TAG 3
+#define Py_TAG_INVALID 2
 #define Py_TAG_REFCNT 1
 #define Py_TAG_BITS 3
 
+static const _PyStackRef PyStackRef_ERROR = { .bits = Py_TAG_INVALID };
+
+static inline bool
+PyStackRef_IsError(_PyStackRef ref)
+{
+    return ref.bits == Py_TAG_INVALID;
+}
+
+static inline bool
+PyStackRef_IsValid(_PyStackRef ref)
+{
+    /* Invalid values are ERROR and NULL */
+    return ref.bits >= Py_INT_TAG;
+}
+
 static inline bool
 PyStackRef_IsTaggedInt(_PyStackRef i)
 {
@@ -284,6 +317,7 @@ PyStackRef_IncrementTaggedIntNoOverflow(_PyStackRef ref)
 
 
 static const _PyStackRef PyStackRef_NULL = { .bits = Py_TAG_DEFERRED};
+
 #define PyStackRef_IsNull(stackref) ((stackref).bits == PyStackRef_NULL.bits)
 #define PyStackRef_True ((_PyStackRef){.bits = ((uintptr_t)&_Py_TrueStruct) | Py_TAG_DEFERRED })
 #define PyStackRef_False ((_PyStackRef){.bits = ((uintptr_t)&_Py_FalseStruct) | Py_TAG_DEFERRED })