[PATCH v2] Handle Python 3.11 deprecation of PySys_SetPath and Py_SetProgramName

[PATCH v2] Handle Python 3.11 deprecation of PySys_SetPath and Py_SetProgramName

[Kevin Buettner]

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 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 PyConfig 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 have 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

This v2 commit also addresses several problems that Simon found in
the v1 version.

In v1, I had used Py_DontWriteBytecodeFlag in the new initialization
code, but Simon pointed out that this global configuration variable
will be deprecated in Python 3.12.  This version of the patch no longer
uses Py_DontWriteBytecodeFlag in the new initialization code.
Additionally, both Py_DontWriteBytecodeFlag and Py_IgnoreEnvironmentFlag
will no longer be used when building GDB against Python 3.10 or higher.
While it's true that both of these global configuration variables are
deprecated in Python 3.12, it makes sense to disable their use for
gdb builds against 3.10 and higher since those are the versions for
which the PyConfig API is now being used by GDB.  (The PyConfig API
includes different mechanisms for making the same settings afforded
by use of the soon-to-be deprecated global configuration variables.)

Simon also noted that PyConfig_Clear() would not have be called for
one of the failure paths.  I've fixed that problem and also made the
rest of the "bail out" code more direct.  In particular,
PyConfig_Clear() will always be called, both for success and failure.
---
 gdb/python/python-internal.h |  5 ++
 gdb/python/python.c          | 88 ++++++++++++++++++++++++++++++++----
 2 files changed, 84 insertions(+), 9 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..0170e75d911 100644
--- a/gdb/python/python.c
+++ b/gdb/python/python.c
@@ -1820,8 +1820,14 @@ set_python_ignore_environment (const char *args, int from_tty,
 			       struct cmd_list_element *c)
 {
 #ifdef HAVE_PYTHON
+  /* Py_IgnoreEnvironmentFlag is deprecated in Python 3.12.  Disable
+     its usage in Python 3.10 and above since the PyConfig mechanism
+     is now (also) used in 3.10 and higher.  See do_start_initialization()
+     in this file.  */
+#if PY_VERSION_HEX < 0x030a0000
   Py_IgnoreEnvironmentFlag = python_ignore_environment ? 1 : 0;
 #endif
+#endif
 }
 
 /* When this is turned on before Python is initialised then Python will
@@ -1849,6 +1855,24 @@ show_python_dont_write_bytecode (struct ui_file *file, int from_tty,
 		value);
 }
 
+/* Return value to assign to PyConfig.write_bytecode or, when
+   negated (via !), Py_DontWriteBytecodeFlag.  Py_DontWriteBytecodeFlag
+   is deprecated in Python 3.12.  */
+
+static int
+python_write_bytecode ()
+{
+  int wbc = 0;
+
+  if (python_dont_write_bytecode == AUTO_BOOLEAN_AUTO)
+    wbc = (!python_ignore_environment
+	    && getenv ("PYTHONDONTWRITEBYTECODE") != nullptr) ? 0 : 1;
+  else
+    wbc = python_dont_write_bytecode == AUTO_BOOLEAN_TRUE ? 0 : 1;
+
+  return wbc;
+}
+
 /* Implement 'set python dont-write-bytecode'.  This sets Python's internal
    flag no matter when the command is issued, however, if this is used
    after Py_Initialize has been called then many modules could already
@@ -1859,13 +1883,13 @@ set_python_dont_write_bytecode (const char *args, int from_tty,
 				struct cmd_list_element *c)
 {
 #ifdef HAVE_PYTHON
-  if (python_dont_write_bytecode == AUTO_BOOLEAN_AUTO)
-    Py_DontWriteBytecodeFlag
-      = (!python_ignore_environment
-	 && getenv ("PYTHONDONTWRITEBYTECODE") != nullptr) ? 1 : 0;
-  else
-    Py_DontWriteBytecodeFlag
-      = python_dont_write_bytecode == AUTO_BOOLEAN_TRUE ? 1 : 0;
+  /* Py_DontWriteBytecodeFlag is deprecated in Python 3.12.  Disable
+     its usage in Python 3.10 and above since the PyConfig mechanism
+     is now (also) used in 3.10 and higher.  See do_start_initialization()
+     in this file.  */
+#if PY_VERSION_HEX < 0x030a0000
+  Py_DontWriteBytecodeFlag = !python_write_bytecode ();
+#endif
 #endif /* HAVE_PYTHON */
 }
 
@@ -2001,16 +2025,51 @@ 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
+  PyConfig config;
+  bool fail = false;
+
+  PyConfig_InitPythonConfig (&config);
+  PyStatus status = PyConfig_SetString (&config, &config.program_name,
+                                        progname_copy);
+  if (PyStatus_Exception (status))
+    goto init_done;
+
+  config.write_bytecode = python_write_bytecode ();
+  config.use_environment = !python_ignore_environment;
+
+  status = PyConfig_Read (&config);
+  if (PyStatus_Exception (status))
+    goto init_done;
+
+  /* Define _gdb as a built-in module.  */
+  if (PyImport_AppendInittab ("_gdb", init__gdb_module) == -1)
+    {
+      fail = true;
+      goto init_done;
+    }
 
+  status = Py_InitializeFromConfig (&config);
+
+init_done:
+  PyConfig_Clear (&config);
+  if (PyStatus_Exception (status) || fail)
+    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 +2376,23 @@ 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

Re: [PATCH v2] Handle Python 3.11 deprecation of PySys_SetPath and Py_SetProgramName

[Tom Tromey]

>>>>> "Kevin" == Kevin Buettner via Gdb-patches <gdb-patches@sourceware.org> writes:

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

This looks good to me.  Thank you for doing this.

I think this fixes a couple of bugs in bugzilla, so those should be
mentioned in the commit message IMO.

Tom

Re: [PATCH v2] Handle Python 3.11 deprecation of PySys_SetPath and Py_SetProgramName

[Kevin Buettner]

On Fri, 15 Jul 2022 12:37:54 -0600
Tom Tromey <tom@tromey.com> wrote:

> >>>>> "Kevin" == Kevin Buettner via Gdb-patches <gdb-patches@sourceware.org> writes:  
> 
> Kevin> Python 3.11 deprecates PySys_SetPath and Py_SetProgramName.  The
> Kevin> PyConfig API replaces these and other functions.  This commit uses the
> Kevin> PyConfig API to provide equivalent functionality while also preserving
> Kevin> support for older versions of Python, i.e. those before Python 3.8.  
> [...]
> 
> This looks good to me.  Thank you for doing this.
> 
> I think this fixes a couple of bugs in bugzilla, so those should be
> mentioned in the commit message IMO.

I ran into some non-trivial conflicts while rebasing, so I'll send out a v3 patch
with the conflicts fixed in addition to mentioning the bugs which were fixed
in the commit message.

Kevin