[PATCH] Handle Python 3.11 deprecation of PySys_SetPath and Py_SetProgramName

[Kevin Buettner <kevinb@redhat.com>]

Python 3.11 deprecates PySys_SetPath and Py_SetProgramName.  The
PyConfig API replaces these and other functions.  This commit uses the
PyConfig API to provide (hopefully) equivalent functionality while
also preserving support for older versions of Python, i.e. those
before Python 3.8.

A beta version of Python 3.11 is available in Fedora Rawhide.  Both
Fedora 35 and Fedora 36 use Python 3.10, while Fedora 34 still used
Python 3.9.  I've tested these changes on Fedora 34, Fedora 36, and
rawhide, though complete testing was not possible on rawhide due to
a kernel bug.  That being the case, I decided to enable the newer
PyConfig API by testing PY_VERSION_HEX against 0x030a0000.  This
corresponds to Python 3.10.

We could try to use the new API for Python versions as early as 3.8,
but I'm reluctant to do this as there may have been PyConfig related
bugs in earlier versions which have since been fixed.  Recent linux
distributions should include support for Python 3.10.  This should be
more than adequate for testing the new Python initialization code in
GDB.

Information about the PyConfig API as well as the motivation behind
deprecating the old interface can be found at these links:

https://github.com/python/cpython/issues/88279
https://peps.python.org/pep-0587/
https://docs.python.org/3.11/c-api/init_config.html
---
 gdb/python/python-internal.h |  5 +++++
 gdb/python/python.c          | 43 ++++++++++++++++++++++++++++++++++--
 2 files changed, 46 insertions(+), 2 deletions(-)

diff --git a/gdb/python/python-internal.h b/gdb/python/python-internal.h
index 5ff9989af83..3dae4e13a4c 100644
--- a/gdb/python/python-internal.h
+++ b/gdb/python/python-internal.h
@@ -177,6 +177,10 @@ gdb_PySys_GetObject (const char *name)
 
 #define PySys_GetObject gdb_PySys_GetObject
 
+/* PySys_SetPath was deprecated in Python 3.11.  Disable the deprecated
+   code for Python 3.10 and newer.  */
+#if PY_VERSION_HEX < 0x030a0000
+
 /* PySys_SetPath's 'path' parameter was missing the 'const' qualifier
    before Python 3.6.  Hence, we wrap it in a function to avoid errors
    when compiled with -Werror.  */
@@ -190,6 +194,7 @@ gdb_PySys_SetPath (const GDB_PYSYS_SETPATH_CHAR *path)
 }
 
 #define PySys_SetPath gdb_PySys_SetPath
+#endif
 
 /* Wrap PyGetSetDef to allow convenient construction with string
    literals.  Unfortunately, PyGetSetDef's 'name' and 'doc' members
diff --git a/gdb/python/python.c b/gdb/python/python.c
index 8f526bba84e..ce42c59f1ae 100644
--- a/gdb/python/python.c
+++ b/gdb/python/python.c
@@ -2001,16 +2001,44 @@ do_start_initialization ()
     }
   setlocale (LC_ALL, oldloc.c_str ());
 
+  /* Py_SetProgramName was deprecated in Python 3.11.  Use PyConfig
+     mechanisms for Python 3.10 and newer.  */
+#if PY_VERSION_HEX < 0x030a0000
   /* Note that Py_SetProgramName expects the string it is passed to
      remain alive for the duration of the program's execution, so
      it is not freed after this call.  */
   Py_SetProgramName (progname_copy);
-
   /* Define _gdb as a built-in module.  */
   PyImport_AppendInittab ("_gdb", init__gdb_module);
-#endif
+  Py_Initialize ();
+#else
+  PyStatus status;
+  PyConfig config;
+
+  PyConfig_InitPythonConfig (&config);
+  status = PyConfig_SetString (&config, &config.program_name, progname_copy);
 
+  config.write_bytecode = !Py_DontWriteBytecodeFlag;
+  config.use_environment = !python_ignore_environment;
+
+  if (!PyStatus_Exception (status))
+    status = PyConfig_Read (&config);
+
+  /* Define _gdb as a built-in module.  */
+  if (PyImport_AppendInittab ("_gdb", init__gdb_module) == -1)
+    return false;
+
+  if (!PyStatus_Exception (status))
+    status = Py_InitializeFromConfig (&config);
+
+  PyConfig_Clear (&config);
+  if (PyStatus_Exception (status))
+    return false;
+#endif
+#else
   Py_Initialize ();
+#endif
+
 #if PY_VERSION_HEX < 0x03090000
   /* PyEval_InitThreads became deprecated in Python 3.9 and will
      be removed in Python 3.11.  Prior to Python 3.7, this call was
@@ -2317,12 +2345,23 @@ do_initialize (const struct extension_language_defn *extlang)
 
   sys_path = PySys_GetObject ("path");
 
+  /* PySys_SetPath was deprecated in Python 3.11.  Disable this
+     deprecated code for Python 3.10 and newer.  Also note that this
+     ifdef eliminates potential initialization of sys.path via
+     PySys_SetPath.  My (kevinb's) understanding of PEP 587 suggests
+     that it's not necessary due to module_search_paths being
+     initialized to an empty list following any of the PyConfig
+     initialization functions.  If it does turn out that some kind of
+     initialization is still needed, it should be added to the
+     PyConfig-based initialization in do_start_initialize().  */
+#if PY_VERSION_HEX < 0x030a0000
   /* If sys.path is not defined yet, define it first.  */
   if (!(sys_path && PyList_Check (sys_path)))
     {
       PySys_SetPath (L"");
       sys_path = PySys_GetObject ("path");
     }
+#endif
   if (sys_path && PyList_Check (sys_path))
     {
       gdbpy_ref<> pythondir (PyUnicode_FromString (gdb_pythondir.c_str ()));
-- 
2.36.1