[fpc-devel] RTTI for ProcVar types

[Steve Hildebrandt]

Am 21.03.2013 22:00, schrieb Sven Barth:
> On 21.03.2013 15:53, Steve Hildebrandt wrote:
>> Am 21.03.2013 11:51, schrieb Sven Barth:
>>> Out of curiosity: Why did you add this?
>> To implement a less "hacky" way of generic method invokation.
>> Supporting several calling conventions I can call a method based on the
>> address and an array of const as parameters.
>> Without RTTI there would've been a need for hard coded meta information,
>> wich is error prone and rather time consuming.
>> Since tkMethod supports RTTI any method contained in a record, class,
>> object would work without additional meta information.
>
> Out of interest: do you support multiple platforms? Maybe if you want 
> to provide your code under modified LGPL we could use it once we have 
> the RTTI.TValue type and the extended RTTI to support RTTI.Invoke.
Sure i can provide the code. Some modifications would be needed, so it 
is easier to adopt it to RTTI.Invoke.
Regarding the platforms:
     Calling conventions 64bit : win64(the microsoft standart thing 
dunno how its called right now)
                                        32bit : stdcall, register.
     Since the inline asm code for the actual call differs depending on 
witch registers are used,
     this part can't be handled in a generic way and needs to be coded 
down for each convention.
     While passing parameters on the Stack works rather generic(well 
obtaining the stack pointer is the exception here).
      Calculation of the stack offset/used register too is dependant on 
the convention.
Hope this sums up what needs to be done to port the approach I took to 
all platforms supported.
>> I'm currently using this to call pascal procedures and use pascal
>> classes in LUA.
>>> Without you showing what you changed we can not help much...
>> typinfo.pp :
>> tkMethod, tkProcVar: // simply added tkProcVar here
>>                (MethodKind : TMethodKind;
>>                 ParamCount : Byte;
>>                 ParamList : array[0..1023] of Char
>> ncgrtti.pas:(Line 690)
>> procedure procvardef_rtti(def:tprocvardef);
>> ...
>> begin
>>    { write method id and name }
>>    if po_methodpointer in def.procoptions
>>      then write_header(def,tkMethod)
>>      else write_header(def,tkProcVar);
>>    maybe_write_align;
>>    ...
>>
>> So that RTTI generation for tkProcVar and tkMethod would only
>> differentiate in the TTypeKind field.
>
> I can reproduce your problem, but I don't have a solution. At least it 
> is enough to only use that unit, so you could copy the unit locally 
> and comment everything until the problem disappears. This way you 
> could pinpoint what construct the problem is and then try to fix the 
> compiler. And if it then works without further problems we could add 
> this to trunk. 
Narrowed it down to those 2 records :
type
   jpeg_entropy_encoder = record
     //test.lpr(23,1) Error: Undefined symbol: RTTI_$JPEGLIB_$$_DEF2
     //ORIGINAL JPEGLib Line 539
     //parameter MCU_data leads to the error
     encode_mcu : function({cinfo : Pointer; }const MCU_data : array of 
Pointer) : boolean;
   end;

   jpeg_entropy_decoder = record
     //test.lpr(23,1) Error: Undefined symbol: RTTI_$JPEGLIB_$$_DEF5
     //ORIGINAL JPEGLib Line 655
     //parameter MCU_data leads to the error
     decode_mcu : function({cinfo : Pointer; }var MCU_data : array of 
Pointer) : boolean;
   end;
But here I'm lost again.

mfg Necem