On 3 October 2016 at 00:51, Peter Wu <pe...@lekensteyn.nl> wrote: > Hi, > > To fix bug 12968 (__gc being called for tables, resulting in lua_error > while exiting), I modified the way how classes are registered in > https://code.wireshark.org/review/18026 > > In these changes I also reduced the use of macros, following Joãos > concerns. Macros like WSLUA_META should most likely become typedefs. > Below I will give a motivation for the changes (feedback welcome!). > > > Consider class Address with function Address.ip and metamethods like > address.__tostring. Previously you could have these strange invocations: > > -- note: "Address" is the global class, "address" is an instance. > tostring(Address) -- invokes metamethod __tostring (error!) > address.ip("foo") -- invokes "static" class function > tostring(FileHandler) -- error > filehandler.new(...) -- huh? > > In the proposed change, there will be different method tables and > metatables for the class ("Address") and its instances ("address"). > Further modification could disable the above badness, allowing just: > > tostring(address) > Address.ip("foo") > tostring(filehandler) > FileHandler.new(...) > > This might break some dissectors that use non-documented invocations, > but enables use of separate __call functions for example: > > field = Field("x") -- __call in metatable of class Field > fields = field() -- __call in metatable of instance of Field > > Also changed is that attributes are no longer visible on the class, only > its instances: > > filehandler.read_open = x -- ok, sets callback attribute > -- previously failed in the setter callback out because "self" is > -- not a FileHandler instance. Now it will already fail while > -- looking up the attribute (in the __newindex metamethod). > FileHandler.read_open = x > > > > Distinct metatables are good, but what about different method tables? > The proposal will also disable invocations like Tvb.len(tvb) assuming > that nobody wants to do it (tvb:len() is saner). > > Any objections with removing __setters/__getters/__methods? > I doubt that dissectors use this. Users can read the WSDG and study the > source code to discover available functions. > > > Future work, in order (assuming the current proposal): > - grep for WSLUA_REGISTER_ATTRIBUTES, change their ClassName_register > functions to use the new wslua_class definition mechanism, including > setting the "attrs" member. > - Remove wslua_reg_attributes and macros. > - grep for WSLUA_REGISTER_META and WSLUA_REGISTER_CLASS to change the > remaining ClassName_register files. > > If you feel that the Lua core code needs some love, help is appreciated > in these tasks :-) > -- > Kind regards, > Peter Wu >
As a non-lua programmer most of that goes straight over my head, but I'm intrigued\concerned about methods that are class based (i.e. similar to C++ class static methods ??) and instance based that differ only by the case of the initial method letter. Is this normal for Lua so won't be a surprise for users, or is it likely to surprise\confuse users and cause lots of issues and support queries? -- Graham Bloice
___________________________________________________________________________ Sent via: Wireshark-dev mailing list <wireshark-dev@wireshark.org> Archives: https://www.wireshark.org/lists/wireshark-dev Unsubscribe: https://www.wireshark.org/mailman/options/wireshark-dev mailto:wireshark-dev-requ...@wireshark.org?subject=unsubscribe
