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
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;

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?

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;

I very much doubt VBA understands the 'array of string' concept. It is typical for pascal.

I think you need to use stdcall calling convention.

No, there is not.

No, IMHO you will need to use pchar everywhere.

Michael.

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 :

Luciano,

you should follow binary compatible DLL requirements :

- stdcall call convention
- ordinal types only (shortstring may work too because they are char[256] and 0-th byte is the length)
- pointers (be attentive: if memory was allocated in DLL, you should free it in DLL too)

You can also use any suggestions and examples for writing DLL in C/C++.

In our previous episode, Michael Van Canneyt said:

VBA might understand WIDESTRING ?