C++ to Delphi dll call - c

Question

I am trying to convert this code to delphi 7
LIBEXPORT int __stdcall MY_GetDLLInfo(const char **pp_version, const char **pp_release_type, const char **pp_build_date, const char **pp_load_path);
// C++ Call Example
const char *p_version = NULL;
const char *p_release_type = NULL;
const char *p_build_date = NULL;
MY_GetDLLInfo(&p_version,&p_release_type,&p_build_date,NULL);
Delphi Code
MY_GetDLLInfo: function (const pp_version:PPAnsiChar;const pp_release_type:PPAnsiChar;const pp_build_date:PPAnsiChar;const pp_load_path:PPAnsiChar): Integer; stdcall;
// Delphi Call Example
var
hHandle:THandle;
p_version,p_release_type,p_build_date,p_load_path:PPAnsiChar;
begin
hHandle := LoadLibrary(Dl_path);
#MY_GetDLLInfo:=GetProcAddress(hHandle, PChar('MY_GetDLLInfo'));
if Assigned(MY_GetDLLInfo) then begin
MY_GetDLLInfo(p_version,p_release_type,p_build_date,#null);
ShowMessage(StrPas(#p_version)); // <- I Get Strange Output
ShowMessage(StrPas(#p_release_type)); // <- I Get Strange Output
ShowMessage(StrPas(#p_build_date)); // <- I Get Strange Output
end;
end;
With my converted code i get strange output
I think i am doing wrong at using strpas ?

Answer 1

char* in C/C++ is PAnsiChar in Delphi, and char** is PPAnsiChar.
Your local string variables need to be declared as PAnsiChar, not as PPAnsiChar, and then you need to use the # address operator (Delphi's equivilent of C/C++'s & address operator) to pass the variables into the function.
Also, null is a Variant in Delphi. To assign a null to a pointer, you need to use nil instead.
Try this:
// Delphi Call Example
var
hHandle: THandle;
MY_GetDLLInfo: function(const pp_version, pp_release_type, pp_build_date, pp_load_path: PPAnsiChar): Integer; stdcall;
p_version, p_release_type, p_build_date: PAnsiChar;
begin
hHandle := LoadLibrary(Dl_path);
if hHandle <> 0 then
begin
#MY_GetDLLInfo := GetProcAddress(hHandle, 'MY_GetDLLInfo');
if Assigned(MY_GetDLLInfo) then
begin
p_version := nil;
p_release_type := nil;
p_build_date := nil;
MY_GetDLLInfo(#p_version, #p_release_type, #p_build_date, nil);
ShowMessage(p_version);
ShowMessage(p_release_type);
ShowMessage(p_build_date);
end;
FreeLibrary(hHandle);
end;
end;