How to call C++ DLL in Delphi with string parameters?

Question

My Delphi application is calling a function from a C++ DLL that should be returning strings like this.

C++ DLL

__declspec( dllexport ) void sample(char* str1, char* str2)
{
    strcpy(str1, "123");
    strcpy(str2, "abc");
}

Delphi

procedure sample(Str1, Str2: pchar); cdecl; external 'cpp.dll';
var
  buf1 : Pchar;
  buf2 : Pchar;
begin
  sample(@buf1, @buf2);
  //display buf1 and buf2
  //ShowMessage(buf1); //it display random ascii characters 
end;

What is the correct way to do this?

It's not very clear what the problem is?

Marco van de Voort
– Marco van de Voort

2014-03-04 10:26:41 +00:00
Commented Mar 4, 2014 at 10:26 — Marco van de Voort
– Marco van de Voort, Commented Mar 4, 2014 at 10:26

David Heffernan · Accepted Answer · 2014-03-04 10:30:01Z

5

You need to allocate memory for the C++ code to write to. For instance:

var
  buf1, buf2: array [0..255] of Char;
begin
  sample(buf1, buf2);
end;

You should also re-design your interface to accept the length of the buffer and so allow the DLL code to avoid buffer overrun.

answered Mar 4, 2014 at 10:30

David Heffernan

616k46 gold badges1.1k silver badges1.5k bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

How to call C++ DLL in Delphi with string parameters?

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related