[New-bugs-announce] [issue28517] Dead code in wordcode

[Serhiy Storchaka]

New submission from Serhiy Storchaka:

>>> def func(test):
...     if test == 1:
...         return 1
...     elif test == 2:
...         return 2
...     return 3
... 
>>> import dis
>>> dis.dis(func)

Python 3.5:

  2           0 LOAD_FAST                0 (test)
              3 LOAD_CONST               1 (1)
              6 COMPARE_OP               2 (==)
              9 POP_JUMP_IF_FALSE       16

  3          12 LOAD_CONST               1 (1)
             15 RETURN_VALUE

  4     >>   16 LOAD_FAST                0 (test)
             19 LOAD_CONST               2 (2)
             22 COMPARE_OP               2 (==)
             25 POP_JUMP_IF_FALSE       32

  5          28 LOAD_CONST               2 (2)
             31 RETURN_VALUE

  6     >>   32 LOAD_CONST               3 (3)
             35 RETURN_VALUE

Python 3.6:

  2           0 LOAD_FAST                0 (test)
              2 LOAD_CONST               1 (1)
              4 COMPARE_OP               2 (==)
              6 POP_JUMP_IF_FALSE       14

  3           8 LOAD_CONST               1 (1)
             10 RETURN_VALUE
             12 JUMP_FORWARD            12 (to 26)

  4     >>   14 LOAD_FAST                0 (test)
             16 LOAD_CONST               2 (2)
             18 COMPARE_OP               2 (==)
             20 POP_JUMP_IF_FALSE       26

  5          22 LOAD_CONST               2 (2)
             24 RETURN_VALUE

  6     >>   26 LOAD_CONST               3 (3)
             28 RETURN_VALUE

Note JUMP_FORWARD after RETURN_VALUE in 3.6 listing.

----------
components: Interpreter Core
messages: 279297
nosy: Demur Rumed, serhiy.storchaka
priority: normal
severity: normal
status: open
title: Dead code in wordcode
type: behavior
versions: Python 3.6, Python 3.7

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue28517>
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