On 08/19/2016 04:18 PM, Pascal Quantin wrote:
2016-08-19 17:05 GMT+02:00 Jo�o Valverde
<joao.valverde@xxxxxxxxxxxxxxxxxx
<mailto:joao.valverde@xxxxxxxxxxxxxxxxxx>>:
On 08/19/2016 03:56 PM, Jo�o Valverde wrote:
On 08/19/2016 02:54 PM, Peter Wu wrote:
On Mon, Aug 08, 2016 at 09:17:35PM +0100, Jo�o Valverde wrote:
On 08/08/2016 05:58 PM, Pascal Quantin wrote:
Hi Jo�o,
2016-08-08 18:52 GMT+02:00 Jo�o Valverde
<joao.valverde@xxxxxxxxxxxxxxxxxx
<mailto:joao.valverde@xxxxxxxxxxxxxxxxxx>
<mailto:joao.valverde@xxxxxxxxxxxxxxxxxx
<mailto:joao.valverde@xxxxxxxxxxxxxxxxxx>>>:
Is moving to Lua 5.3 something we should look into?
The 64 bit integer support seems really promising.
Hariel explained us that Lua 5.3 was a completely
different language (a
bit like what you have between Python 2.X and 3.X).
You can find much
more info (from people knowing what they are taling
about - so not me
;)) in bug 10881.
Pascal.
Thanks for that Pascal. The only sane way to approach
the issue IMHO
is to
accept that this may and probably will break backward
compatibility (not
even think about supporting 5.1 or 5.2) and just
consider whether
that break
is justified (hint: it is).
Why is it justified to break backwards compatibility and
move from 5.2
to 5.3 without the ability to chose for 5.2? What is the
killer feature
of 5.3 that makes it totally worth to possibly break older
dissectors?
The disadvantage of C plugins is that it had to be
recompiled for newer
versions. With a move from 5.2 to 5.3 and also removing
GRegex and bitop
you make it quite likely to break Lua dissectors in some way.
I have once written a Lua library in C, interfacing with
Libgcrypt for
which I studied the Lua manual. The API changes with 5.3
were not that
significant if I remember correctly (though you have to be
careful with
providing a compatibility layer), but the ABI is certainly not
compatible.
In the recent proposed patches, you seem to have no issues
with breaking
backwards compatibility. Have you developed Lua dissectors
before?
Breaking things for the sake of "shiny, new, future" is not an
acceptable motivation, there must be something more
appealing to justify
such breakage. Having 64-bit integer support, but taking
away the bitop
library is a net loss without even considering the other
factors.
Doesn't Lua 5.3 provide native bit operators? If so there is not net
loss of functionality. That was my reasoning at least.
The language incompatibilities between 5.2 and 5.3 are minor. The
wireshark API is exactly the same.
LPeg is more powerful and Lua-thonic than lrexlib, but there is a
learning curve for that, no doubt. For anyone relying on
lrexlib, it's a
significant break. We can keep lrexlib, that's not a problem and
it is
orthogonal to the other changes.
As far as killer features go, besides the obvious, how about better
UTF-8 support?
I don't have time for a more detailed answer right now but I'd
like to
say I think this change is entirely justified but I also completely
understand disagreeing with that opinion.
I'm referring to the upgrade to Lua 5.3 here, i.e, breaking backward
compatibility, same as any other Lua script moving from 5.1/5.2 to 5.3.
For what it is worth, I do not remember any user asking / pushing to
upgrade to Lua 5.3 yet. Breaking their script should be justified by a
huge win (I will not judge myself whether this is the case or not with
this upgrade as I'm not a Lua user, so I'm not qualified here; but we
must think about our existing users). C plugins are a bit of main to
recompile for each version, but are fast. ON the other side Lua scripts
were not as impacted as C ones with API changes, but are slower (from
what I understood). Any big change here should be done with caution I think.
I think the impact is very small compared to the benefits, it's an easy
port to Lua 5.3 if it requires porting at all, but maybe someone else
who uses this code heavily can comment on that.
I really like the Wireshark Lua API, by the way. It's really cool.
