Objects/structseq.c: warning: 'strncpy' specified bound depends on the length of the source argument

[vstinner]

BPO	36365
Nosy	@vstinner
PRs	bpo-36365: Rewrite structseq_repr() using _PyUnicodeWriter #12440 [3.7] bpo-36365: Fix compiler warning in structseq.c #12451

^{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 = None
closed_at = <Date 2019-03-19.23:06:20.175>
created_at = <Date 2019-03-19.14:57:37.473>
labels = ['interpreter-core', '3.8']
title = "Objects/structseq.c: warning: 'strncpy' specified bound depends on the length of the source argument"
updated_at = <Date 2019-03-19.23:32:21.585>
user = 'https://github.com/vstinner'

bugs.python.org fields:

activity = <Date 2019-03-19.23:32:21.585>
actor = 'vstinner'
assignee = 'none'
closed = True
closed_date = <Date 2019-03-19.23:06:20.175>
closer = 'vstinner'
components = ['Interpreter Core']
creation = <Date 2019-03-19.14:57:37.473>
creator = 'vstinner'
dependencies = []
files = []
hgrepos = []
issue_num = 36365
keywords = ['patch']
message_count = 3.0
messages = ['338361', '338416', '338419']
nosy_count = 1.0
nosy_names = ['vstinner']
pr_nums = ['12440', '12451']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue36365'
versions = ['Python 3.8']

[vstinner]

Warning seen on Fedora 29 with GCC 8.3.1 20190223 (Red Hat 8.3.1-2):

Objects/structseq.c: In function 'structseq_repr':
Objects/structseq.c:187:5: warning: 'strncpy' specified bound depends on the length of the source argument [-Wstringop-overflow=]
strncpy(pbuf, typ->tp_name, len);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Objects/structseq.c:185:11: note: length computed here
len = strlen(typ->tp_name) > TYPE_MAXSIZE ? TYPE_MAXSIZE :
^~~~~~~~~~~~~~~~~~~~

Attached PR rewrites structseq_repr() using _PyUnicodeWriter for better performance and remove the arbitrary limit of 512 bytes.

[vstinner]

New changeset c70ab02 by Victor Stinner in branch 'master':
bpo-36365: Rewrite structseq_repr() using _PyUnicodeWriter (GH-12440)
c70ab02

[vstinner]

New changeset ea3592d by Victor Stinner in branch '3.7':
bpo-36365: Fix compiler warning in structseq.c (GH-12451)
ea3592d