Improve support of FORMAT_VALUE in dis

[serhiy-storchaka]

BPO	28317
Nosy	@ericvsmith, @serhiy-storchaka
PRs	[Do Not Merge] Convert Misc/NEWS so that it is managed by towncrier #552
Files	dis_format_string.patch

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = 'https://github.com/serhiy-storchaka'
closed_at = <Date 2016-10-08.09:35:45.202>
created_at = <Date 2016-09-30.14:21:20.517>
labels = ['3.7', 'type-feature', 'library']
title = 'Improve support of FORMAT_VALUE in dis'
updated_at = <Date 2017-03-31.16:36:26.410>
user = 'https://github.com/serhiy-storchaka'

bugs.python.org fields:

activity = <Date 2017-03-31.16:36:26.410>
actor = 'dstufft'
assignee = 'serhiy.storchaka'
closed = True
closed_date = <Date 2016-10-08.09:35:45.202>
closer = 'serhiy.storchaka'
components = ['Library (Lib)']
creation = <Date 2016-09-30.14:21:20.517>
creator = 'serhiy.storchaka'
dependencies = []
files = ['44892']
hgrepos = []
issue_num = 28317
keywords = ['patch']
message_count = 2.0
messages = ['277754', '278288']
nosy_count = 3.0
nosy_names = ['eric.smith', 'python-dev', 'serhiy.storchaka']
pr_nums = ['552']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue28317'
versions = ['Python 3.6', 'Python 3.7']

[serhiy-storchaka]

FORMAT_VALUE packs the information about conversion flags and boolean flag that denotes whether format specifier is passed on the stack in one integer argument. It is not easy to decode this information in disassemble output. Proposed patch makes disassembler producing human readable representation of FORMAT_VALUE argument.

$ echo 'f"{a} {b:4} {c!r} {d!r:4}"' | ./python -m dis
  1           0 LOAD_NAME                0 (a)
              2 FORMAT_VALUE             0
              4 LOAD_CONST               0 (' ')
              6 LOAD_NAME                1 (b)
              8 LOAD_CONST               1 ('4')
             10 FORMAT_VALUE             4 (with format)
             12 LOAD_CONST               0 (' ')
             14 LOAD_NAME                2 (c)
             16 FORMAT_VALUE             2 (repr)
             18 LOAD_CONST               0 (' ')
             20 LOAD_NAME                3 (d)
             22 LOAD_CONST               1 ('4')
             24 FORMAT_VALUE             6 (repr, with format)
             26 BUILD_STRING             7
             28 POP_TOP
             30 LOAD_CONST               2 (None)
             32 RETURN_VALUE

[python-dev]

New changeset 5e81d14a52f7 by Serhiy Storchaka in branch '3.6':
Issue bpo-28317: The disassembler now decodes FORMAT_VALUE argument.
https://hg.python.org/cpython/rev/5e81d14a52f7

New changeset 085944763f3a by Serhiy Storchaka in branch 'default':
Issue bpo-28317: The disassembler now decodes FORMAT_VALUE argument.
https://hg.python.org/cpython/rev/085944763f3a