[fpc-pascal] Writing a DLL to be use in a VBA code

[luciano de souza]

Thank you for the always rapid and gentile reply. Well, if there's no
way to avoid pchar, let's go to pchar!

2015-06-06 4:27 GMT-03:00, Michael Van Canneyt <michael at freepascal.org>:
>
>
> On Sat, 6 Jun 2015, luciano de souza wrote:
>
>> Hello all,
>>
>> At work, I need to create a Excel sheet containing certain more
>> complex functions. I tried to use only VBA, but I released I will more
>> productive if I could use a DLL writen in Pascal for the heavier code.
>>
>> Let see this DLL:
>>
>> library test;
>> {$mode objfpc}{$H+}
>>
>> function concatenate(name: string): string; cdecl;
>> begin
>> result := 'Freepascal ' + name;
>> end;
>>
>> function first(names: array of string):string; cdecl; // Warning:
>> cdecl'ared functions have no high parameter
>
> I very much doubt VBA understands the 'array of string' concept.
> It is typical for pascal.
>
>> begin
>> result := names[0];
>> end;
>>
>> exports
>> concatenate;
>> first;
>> end.
>>
>> The compiler also raised this error: "test.pas(10,1) Fatal: Internal
>> error 201003031".
>>
>> I don't know what I am doing wrong. But actually, the reason of my
>> message started from another point.
>>
>> Freepascal codes works with strings as usual. DLLs works with pchar. I
>> could have declared the functions as the following:
>>
>> function concatenate(name: pchar): pchar; cdecl;
>> function first(names: array of pchar): pchar; cdecl;
>
> I think you need to use stdcall calling convention.
>
>>
>> In the body of the functions, I would treat the conversions from pchar
>> to string and from string to pchar again. But, when I used "cdecl", am
>> I making this conversion automatically? Is there a compilation switch
>> that allows me to write strings and the compiled code having correctly
>> treated the allocations and disallocation of strings?
>
> No, there is not.
>
>>
>> Suppose this VBA code:
>>
>> public declare function concatenate lib "test" (name as string) as string
>>
>> Is this the correct way to write the called function in Freepascal?
>>
>> function concatenate(name: string): string; cdecl;
>> begin
>> result := 'Freepascal ' + name;
>> end;
>
> No, IMHO you will need to use pchar everywhere.
>
> Michael.
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>


-- 
Luciano de Souza