gdb/python: remove Python 2 support

New in this version:

 - Add a PY_MAJOR_VERSION check in configure.ac / AC_TRY_LIBPYTHON.  If
   the user passes --with-python=python2, this will cause a configure
   failure saying that GDB only supports Python 3.

Support for Python 2 is a maintenance burden for any patches touching
Python support.  Among others, the differences between Python 2 and 3
string and integer types are subtle.  It requires a lot of effort and
thinking to get something that behaves correctly on both.  And that's if
the author and reviewer of the patch even remember to test with Python
2.

See this thread for an example:

  https://sourceware.org/pipermail/gdb-patches/2021-December/184260.html

So, remove Python 2 support.  Update the documentation to state that GDB
can be built against Python 3 (as opposed to Python 2 or 3).

Update all the spots that use:

 - sys.version_info
 - IS_PY3K
 - PY_MAJOR_VERSION
 - gdb_py_is_py3k

... to only keep the Python 3 portions and drop the use of some
now-removed compatibility macros.

I did not update the configure script more than just removing the
explicit references to Python 2.  We could maybe do more there, like
check the Python version and reject it if that version is not
supported.  Otherwise (with this patch), things will only fail at
compile time, so it won't really be clear to the user that they are
trying to use an unsupported Python version.  But I'm a bit lost in the
configure code that checks for Python, so I kept that for later.

Change-Id: I75b0f79c148afbe3c07ac664cfa9cade052c0c62

1 files changed, 2 insertions, 45 deletions

diff --git a/gdb/python/py-utils.c b/gdb/python/py-utils.c
index 838853c..e7b147c 100644
--- a/gdb/python/py-utils.c
+++ b/gdb/python/py-utils.c
@@ -45,14 +45,10 @@ python_string_to_unicode (PyObject *obj)
       unicode_str = obj;
       Py_INCREF (obj);
     }
-#ifndef IS_PY3K
-  else if (PyString_Check (obj))
-    unicode_str = PyUnicode_FromEncodedObject (obj, host_charset (), NULL);
-#endif
   else
     {
       PyErr_SetString (PyExc_TypeError,
-		       _("Expected a string or unicode object."));
+		       _("Expected a string object."));
       unicode_str = NULL;
     }
 
@@ -166,11 +162,7 @@ host_string_to_python_string (const char *str)
 int
 gdbpy_is_string (PyObject *obj)
 {
-#ifdef IS_PY3K
   return PyUnicode_Check (obj);
-#else
-  return PyString_Check (obj) || PyUnicode_Check (obj);
-#endif
 }
 
 /* Return the string representation of OBJ, i.e., str (obj).
@@ -182,17 +174,7 @@ gdbpy_obj_to_string (PyObject *obj)
   gdbpy_ref<> str_obj (PyObject_Str (obj));
 
   if (str_obj != NULL)
-    {
-      gdb::unique_xmalloc_ptr<char> msg;
-
-#ifdef IS_PY3K
-      msg = python_string_to_host_string (str_obj.get ());
-#else
-      msg.reset (xstrdup (PyString_AsString (str_obj.get ())));
-#endif
-
-      return msg;
-    }
+    return python_string_to_host_string (str_obj.get ());
 
   return NULL;
 }
@@ -296,20 +278,9 @@ get_addr_from_python (PyObject *obj, CORE_ADDR *addr)
 gdbpy_ref<>
 gdb_py_object_from_longest (LONGEST l)
 {
-#ifdef IS_PY3K
   if (sizeof (l) > sizeof (long))
     return gdbpy_ref<> (PyLong_FromLongLong (l));
   return gdbpy_ref<> (PyLong_FromLong (l));
-#else
-#ifdef HAVE_LONG_LONG		/* Defined by Python.  */
-  /* If we have 'long long', and the value overflows a 'long', use a
-     Python Long; otherwise use a Python Int.  */
-  if (sizeof (l) > sizeof (long)
-      && (l > PyInt_GetMax () || l < (- (LONGEST) PyInt_GetMax ()) - 1))
-    return gdbpy_ref<> (PyLong_FromLongLong (l));
-#endif
-  return gdbpy_ref<> (PyInt_FromLong (l));
-#endif
 }
 
 /* Convert a ULONGEST to the appropriate Python object -- either an
@@ -318,23 +289,9 @@ gdb_py_object_from_longest (LONGEST l)
 gdbpy_ref<>
 gdb_py_object_from_ulongest (ULONGEST l)
 {
-#ifdef IS_PY3K
   if (sizeof (l) > sizeof (unsigned long))
     return gdbpy_ref<> (PyLong_FromUnsignedLongLong (l));
   return gdbpy_ref<> (PyLong_FromUnsignedLong (l));
-#else
-#ifdef HAVE_LONG_LONG		/* Defined by Python.  */
-  /* If we have 'long long', and the value overflows a 'long', use a
-     Python Long; otherwise use a Python Int.  */
-  if (sizeof (l) > sizeof (unsigned long) && l > PyInt_GetMax ())
-    return gdbpy_ref<> (PyLong_FromUnsignedLongLong (l));
-#endif
-
-  if (l > PyInt_GetMax ())
-    return gdbpy_ref<> (PyLong_FromUnsignedLong (l));
-
-  return gdbpy_ref<> (PyInt_FromLong (l));
-#endif
 }
 
 /* Like PyInt_AsLong, but returns 0 on failure, 1 on success, and puts