[PATCH 1/2] [gdb/python] Add init_py_immortals

[Tom de Vries <tdevries@suse.de>]

Add and call init_py_immortals, allowing to use "return Py_None" instead of
Py_RETURN_NONE, and likewise for Py_RETURN_{TRUE,FALSE}.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=34145
---
 gdb/python/python.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/gdb/python/python.c b/gdb/python/python.c
index 502fe682b2c..d4c3454bbee 100644
--- a/gdb/python/python.c
+++ b/gdb/python/python.c
@@ -2587,6 +2587,25 @@ py_initialize ()
 #endif
 }
 
+/* Increase the refcount for Py_None/Py_True/Py_False, if necessary.  This
+   allows us to use a simple "return Py_None" instead of Py_RETURN_NONE
+   everywhere else.  */
+
+static void
+init_py_immortals ()
+{
+  [[maybe_unused]] static PyObject *py_none = nullptr;
+  [[maybe_unused]] static PyObject *py_true = nullptr;
+  [[maybe_unused]] static PyObject *py_false = nullptr;
+
+  gdb_assert (py_none == nullptr);
+
+  /* Increase refcount for Py_None/Py_True/Py_False, if necessary.  */
+  py_none = [] { Py_RETURN_NONE; } ();
+  py_true = [] { Py_RETURN_TRUE; } ();
+  py_false = [] { Py_RETURN_FALSE; } ();
+}
+
 static bool
 do_start_initialization ()
 {
@@ -2606,6 +2625,8 @@ do_start_initialization ()
   PyEval_InitThreads ();
 #endif
 
+  init_py_immortals ();
+
   gdb_module = PyImport_ImportModule ("_gdb");
   if (gdb_module == NULL)
     return false;
-- 
2.51.0