Wireshark-bugs: [Wireshark-bugs] [Bug 12968] New: Lua metatable problems (__gc being invoked for
| Bug ID |
12968
|
| Summary |
Lua metatable problems (__gc being invoked for table types)
|
| Product |
Wireshark
|
| Version |
Git
|
| Hardware |
All
|
| OS |
All
|
| Status |
UNCONFIRMED
|
| Severity |
Major
|
| Priority |
Low
|
| Component |
Common utilities (libwsutil)
|
| Assignee |
bugzilla-admin@wireshark.org
|
| Reporter |
peter@lekensteyn.nl
|
| CC |
hadrielk@yahoo.com
|
Build Information:
TShark (Wireshark) 2.3.0 (v2.3.0rc0-880-gfdbf443 from master)
Copyright 1998-2016 Gerald Combs <gerald@wireshark.org> and contributors.
License GPLv2+: GNU GPL version 2 or later
<http://www.gnu.org/licenses/old-licenses/gpl-2.0.html>
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
Compiled (64-bit) with libpcap, with POSIX capabilities (Linux), with libnl 3,
with GLib 2.48.2, with zlib 1.2.8, without SMI, with c-ares 1.11.0, with Lua
5.2.4, with GnuTLS 3.4.15, with Gcrypt 1.7.3, with MIT Kerberos, with GeoIP.
Running on Linux 4.7.2-1-ARCH, with Intel(R) Core(TM) i7-6700HQ CPU @ 2.60GHz
(with SSE4.2), with 31996 MB of physical memory, with locale en_GB.UTF-8, with
libpcap version 1.7.4, with GnuTLS 3.4.15, with Gcrypt 1.7.3, with zlib 1.2.8.
Built using gcc 6.2.1 20160830.
--
On exiting Wireshark, surprisingly lua_error is raised during garbage
collection (for instance, TvbRange__gc). This can be reproduced with an empty
pcap and a simple Lua dissector.
The problem is that all classes are registered as a table with metatables set
on both the class instances (OK) and the class table itself (bad). Metamethods
like __gc and __tostring only make sense for the class instances, not the class
itself. The only metamethod that remotely makes sense for class methods is
__call (and maybe in weird cases __index and __newindex?).
Proposal: use two different metatables for instances and class methods.
This also removes the limitation of one __call function. Instead of:
field = Field.new("some.field")
fieldinfos = field()
we could add a new __call method that enables:
field = Field("some.field")
fieldinfos = field()
As a bonus, weird things like Tvb() (instead of tvb()) will also not be
possible anymore. This will change the API, but should not affect many as you
would have to be a special user that introspects via __metatable.
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