gh-146462: add dict introspection debug offsets

Author: pablogsal

Doc/howto/remote_debugging.rst

@@ -365,6 +365,12 @@ To read and check the debug offsets, follow these steps:
    fields in memory. If any check fails, the debugger should stop the operation
    to avoid reading memory in the wrong format.
 
+For object introspection, ``_Py_DebugOffsets`` also exposes layout metadata for
+``PyTypeObject`` and ``PyHeapTypeObject``. In particular,
+``type_object.tp_basicsize``, ``type_object.tp_dictoffset``, and
+``heap_type_object.ht_cached_keys`` let read-only tools locate instance
+dictionary storage and recover the inline-values key order for heap types.
+
 The following is an example implementation that reads and checks
 ``_Py_DebugOffsets``::
 

Include/internal/pycore_debug_offsets.h

@@ -158,8 +158,16 @@ typedef struct _Py_DebugOffsets {
         uint64_t tp_name;
         uint64_t tp_repr;
         uint64_t tp_flags;
+        uint64_t tp_basicsize;
+        uint64_t tp_dictoffset;
     } type_object;
 
+    // PyHeapTypeObject offset;
+    struct _heap_type_object {
+        uint64_t size;
+        uint64_t ht_cached_keys;
+    } heap_type_object;
+
     // PyTuple object offset;
     struct _tuple_object {
         uint64_t size;
@@ -329,6 +337,12 @@ typedef struct _Py_DebugOffsets {
         .tp_name = offsetof(PyTypeObject, tp_name), \
         .tp_repr = offsetof(PyTypeObject, tp_repr), \
         .tp_flags = offsetof(PyTypeObject, tp_flags), \
+        .tp_basicsize = offsetof(PyTypeObject, tp_basicsize), \
+        .tp_dictoffset = offsetof(PyTypeObject, tp_dictoffset), \
+    }, \
+    .heap_type_object = { \
+        .size = sizeof(PyHeapTypeObject), \
+        .ht_cached_keys = offsetof(PyHeapTypeObject, ht_cached_keys), \
     }, \
     .tuple_object = { \
         .size = sizeof(PyTupleObject), \

Misc/NEWS.d/next/Core_and_Builtins/2026-04-15-12-00-00.gh-issue-146462.1YfK6v.rst

@@ -0,0 +1,3 @@
+Added ``PyTypeObject.tp_basicsize``, ``PyTypeObject.tp_dictoffset``, and
+``PyHeapTypeObject.ht_cached_keys`` offsets to :c:type:`!_Py_DebugOffsets` to
+support version-independent read-only dict introspection tools.

Modules/_remote_debugging/debug_offsets_validation.h

@@ -31,7 +31,7 @@
 #define FIELD_SIZE(type, member) sizeof(((type *)0)->member)
 
 enum {
-    PY_REMOTE_DEBUG_OFFSETS_TOTAL_SIZE = 840,
+    PY_REMOTE_DEBUG_OFFSETS_TOTAL_SIZE = 872,
     PY_REMOTE_ASYNC_DEBUG_OFFSETS_TOTAL_SIZE = 104,
 };