Handle pyston and unkown bytecodes better

Author: rocky

xdis/codetype/code20.py

@@ -1,4 +1,4 @@
-# (C) Copyright 2017-2021, 2023-2024 by Rocky Bernstein
+# (C) Copyright 2017-2021, 2023-2025 by Rocky Bernstein
 #
 #  This program is free software; you can redistribute it and/or
 #  modify it under the terms of the GNU General Public License
@@ -32,6 +32,9 @@
 )
 # co_firstlineno added since 1.x
 
+# Early pyston 2.7 Code objects seem to be a subset of 2.0 code.
+# The fields it has are:
+#   co_argcount, co_filename, co_firstline, co_flag, co_name, co_varnames
 
 class Code2(Code15):
     """Class for a Python2 code object used when a Python 3 interpreter is

xdis/load.py

@@ -222,9 +222,6 @@ def load_module_from_file_object(
             # FIXME: use the internal routine below
             tuple_version = magic_int2tuple(magic_int)
         except KeyError:
-            if magic_int in (2657, 22138):
-                raise ImportError("This smells like Pyston which is not supported.")
-
             if len(magic) >= 2:
                 raise ImportError(
                     "Unknown magic number %s in %s"
@@ -233,6 +230,10 @@ def load_module_from_file_object(
             else:
                 raise ImportError(f"Bad magic number: '{magic}'")
 
+        if magic_int in (2657, 22138):
+            version = magicint2version.get(magic_int, "")
+            raise ImportError(f"Magic int {magic_int} ({version}) is not supported.")
+
         if magic_int in (
             3010,
             3020,
@@ -300,7 +301,11 @@ def load_module_from_file_object(
                     source_size = unpack("<I", fp.read(4))[0]  # size mod 2**32
                     pass
             else:
-                timestamp = unpack("<I", ts)[0]
+
+                # Early Pyston targeting 2.7 doesn't seem to have a timestamp!
+                if magic_int not in (2657,):
+                    timestamp = unpack("<I", ts)[0]
+
                 # Note: a higher magic number doesn't necessarily mean a later
                 # release.  At Python 3.0 the magic number decreased
                 # significantly. Hence, the range below. Also note inclusion of
@@ -310,7 +315,7 @@ def load_module_from_file_object(
                 if (
                     (3200 <= magic_int < 20121)
                     and version >= (1, 5)
-                    or magic_int in PYPY3_MAGICS
+                    or magic_int in list(PYPY3_MAGICS) + [2657]
                 ):
                     source_size = unpack("<I", fp.read(4))[0]  # size mod 2**32