gh-101659: Isolate "obmalloc" State to Each Interpreter (gh-101660)

This is strictly about moving the "obmalloc" runtime state from
`_PyRuntimeState` to `PyInterpreterState`.  Doing so improves isolation
between interpreters, specifically most of the memory (incl. objects)
allocated for each interpreter's use.  This is important for a
per-interpreter GIL, but such isolation is valuable even without it.

FWIW, a per-interpreter obmalloc is the proverbial
canary-in-the-coalmine when it comes to the isolation of objects between
interpreters.  Any object that leaks (unintentionally) to another
interpreter is highly likely to cause a crash (on debug builds at
least).  That's a useful thing to know, relative to interpreter
isolation.

1 files changed, 4 insertions, 1 deletions

diff --git a/Include/internal/pycore_interp.h b/Include/internal/pycore_interp.h
index 86ae3d8..7276ce3 100644
--- a/Include/internal/pycore_interp.h
+++ b/Include/internal/pycore_interp.h
@@ -23,11 +23,12 @@ extern "C" {
 #include "pycore_function.h"      // FUNC_MAX_WATCHERS
 #include "pycore_genobject.h"     // struct _Py_async_gen_state
 #include "pycore_gc.h"            // struct _gc_runtime_state
+#include "pycore_global_objects.h"  // struct _Py_interp_static_objects
 #include "pycore_import.h"        // struct _import_state
 #include "pycore_instruments.h"   // PY_MONITORING_EVENTS
 #include "pycore_list.h"          // struct _Py_list_state
-#include "pycore_global_objects.h"  // struct _Py_interp_static_objects
 #include "pycore_object_state.h"   // struct _py_object_state
+#include "pycore_obmalloc.h"      // struct obmalloc_state
 #include "pycore_tuple.h"         // struct _Py_tuple_state
 #include "pycore_typeobject.h"    // struct type_cache
 #include "pycore_unicodeobject.h" // struct _Py_unicode_state
@@ -82,6 +83,8 @@ struct _is {
     int _initialized;
     int finalizing;
 
+    struct _obmalloc_state obmalloc;
+
     struct _ceval_state ceval;
     struct _gc_runtime_state gc;