Merge pull request #132 from MatthieuDartiailh/encode_varint_fixes

Fix encoding of 0 in varint

Author: MatthieuDartiailh

doc/changelog.rst

@@ -6,6 +6,7 @@ ChangeLog
 
 Bugfixes:
 
+- Fixes encoding of 0 as a varint PR #132
 - Correct spelling of "INTRINSIC" in several places; this affected
   some ops in Python 3.12.  PR #131
 

src/bytecode/concrete.py

@@ -818,9 +818,10 @@ def _encode_varint(value: int, set_begin_marker: bool = False) -> Iterator[int]:
         while value:
             temp.append(value & 63 | (64 if temp else 0))
             value >>= 6
+        temp = temp or [0]
         if set_begin_marker:
             temp[-1] |= 128
-        return reversed(temp or [0])
+        return reversed(temp)
 
     def _assemble_exception_table(self) -> bytes:
         table = bytearray()

tests/test_concrete.py

@@ -529,7 +529,6 @@ def test_cellvar_freevar(self):
             ],
         )
 
-    # XXX adjust test for 3.12 in which load_classderef does not exist anymore
     def test_load_classderef(self):
         i_name = (
             "LOAD_FROM_DICT_OR_DEREF"
@@ -682,6 +681,11 @@ def test_copy(self):
         )
         self.assertInstructionListEqual(concrete, concrete.copy())
 
+    def test_encode_varint(self):
+        self.assertListEqual(list(ConcreteBytecode._encode_varint(0)), [0])
+        self.assertListEqual(list(ConcreteBytecode._encode_varint(0, True)), [128])
+        self.assertListEqual(list(ConcreteBytecode._encode_varint(64, False)), [65, 0])
+
 
 class ConcreteFromCodeTests(TestCase):
     def test_extended_arg(self):