1 files changed, 29 insertions, 1 deletions
diff --git a/Include/internal/pycore_interp.h b/Include/internal/pycore_interp.h
index d48ea87fd67..77e42b65f5d 100644
--- a/Include/internal/pycore_interp.h
+++ b/Include/internal/pycore_interp.h
@@ -8,6 +8,8 @@ extern "C" {
 #  error "this header requires Py_BUILD_CORE define"
 #endif
 
+#include <stdbool.h>
+
 #include "pycore_atomic.h"        // _Py_atomic_address
 #include "pycore_ast_state.h"     // struct ast_state
 #include "pycore_context.h"       // struct _Py_context_state
@@ -70,13 +72,18 @@ struct atexit_state {
 
 /* interpreter state */
 
-// The PyInterpreterState typedef is in Include/pystate.h.
+/* PyInterpreterState holds the global state for one of the runtime's
+   interpreters.  Typically the initial (main) interpreter is the only one.
+
+   The PyInterpreterState typedef is in Include/pystate.h.
+   */
 struct _is {
 
     struct _is *next;
 
     struct pythreads {
         uint64_t next_unique_id;
+        /* The linked list of threads, newest first. */
         struct _ts *head;
         /* Used in Modules/_threadmodule.c. */
         long count;
@@ -104,6 +111,9 @@ struct _is {
     int _initialized;
     int finalizing;
 
+    /* Was this interpreter statically allocated? */
+    bool _static;
+
     struct _ceval_state ceval;
     struct _gc_runtime_state gc;
 
@@ -166,8 +176,26 @@ struct _is {
 
     struct ast_state ast;
     struct type_cache type_cache;
+
+    /* The following fields are here to avoid allocation during init.
+       The data is exposed through PyInterpreterState pointer fields.
+       These fields should not be accessed directly outside of init.
+
+       All other PyInterpreterState pointer fields are populated when
+       needed and default to NULL.
+
+       For now there are some exceptions to that rule, which require
+       allocation during init.  These will be addressed on a case-by-case
+       basis.  Also see _PyRuntimeState regarding the various mutex fields.
+       */
+
+    /* the initial PyInterpreterState.threads.head */
+    struct _ts _initial_thread;
 };
 
+
+/* other API */
+
 extern void _PyInterpreterState_ClearModules(PyInterpreterState *interp);
 extern void _PyInterpreterState_Clear(PyThreadState *tstate);