[fpc-pascal] assign code to a method

[Angel Montesinos]

While waiting for a 64 bits Delphi, I am doing experimentation with 
fpc-Lazarus 64 bits. And this is my problem:

In most of my programs I use my own library for parsing and evaluating 
floating point functions like

   'x sin(y z)'

passed by the user as strings. The basic organization is as follows:

{---------------simplified code------------}

   TFunctionEvaluator= class(TObject)
       ...
       code: AnsiString;
       ...
     public
          {call the parser}
       function ParseAFunctText(t, vars: AnsiString): AnsiString;

          {call the evaluator}
       V: function(X: array of Double): Double;
   end;

{----------end code------------------------}


Suppose that  "theF"  is an already created instance of 
TFunctionEvaluator and suppose that a program calls

   msg:= theF.ParseAFunctText('pi', 'xyz');

Here, 'pi' is the text of the constant funcion that must give 3.14... 
as result, 'xyz' contains the chars in the function text that the 
parser should take as independent variables if they appear in  t. The 
result will be an error message "msg" if something fails. Then 
ParseAFunctText builds "code" and puts

    @V:= PChar(code);

Suppose that a program calls for example

    r:= theF.V([1, 2, 3]);

Then Lazarus (fpc 2.2.4, lazarus 0.9.28.2 beta, target windows 64 
bits, mode Delphi) compiles, but it raises an

     'External:SIGSEGV' error.

In the debugger the exception is raised before the effective call of 
the function code. If then I press F7, then the debugger jumps to the 
following assemblies

    push    %rbp
    mov     %esp,%ebp
    fldpi                       {loads pi to the fpu}
    ftspl   -0x18(%rbp)         {copy pi to stack}
    movsd   -0x18(%rbp),%xmm0   {copies pi to XMM0, so caller
                                {may find also there the result}
    leaveq
    retq

I have tried all possible combinations like V:= PChar(code), V:= 
@code[1], etc. to no avail. Thus I think something is wrong in my 
understanding of the whole business in 64 bits or in fpc-Lazarus, 
because this is not a problem in Delphi nor it was in an old version 
of fpc-Lazarus 32 bits. Please give me a tip.
Many thanks in advance.

-- 
montesin at uv dot es