[fpc-pascal] DLL call works on FPC 2.6.4 but not with D7

[Paul Breneman]

On 07/01/2014 10:59 AM, Paul Breneman wrote:
> Below is code from a C program (that works).
>
>  From the ".h" files:
> typedef uint32_t PICO_INFO;
> typedef uint32_t PICO_STATUS;
>
> PREF0 PREF1 PICO_STATUS PREF2 PREF3 (ps5000aGetUnitInfo)
> (
>    int16_t      handle,
>    int8_t        *  string,
>    int16_t      stringLength,
>    int16_t     *requiredSize,
>    PICO_INFO  info
> );
>
>  From a ".c" program:
>      int16_t i = 0;
>      int16_t requiredSize = 0;
>      int8_t line [10];
>      PICO_STATUS status = PICO_OK;
> status = ps5000aGetUnitInfo(unit->handle, line, sizeof (line),
> &requiredSize, i);
>
> **************
>
> Here is the dll call I'm having trouble with:
> function ps5000aGetUnitInfo
>           (handle : smallInt;
>            var str : Pchar;
>            stringLength : smallInt;
>            var requiredSize : smallInt;
>            info : integer
>            ) : integer;
> {$IFDEF WIN32} stdcall; external 'ps5000a.dll';{$ENDIF}
>
> I have two console programs that are almost identical.
>
> Here is my FPC 2.6.4 call (that works):
>        Status := ps5000aGetUnitInfo( ps5000a_handle, MyReturnStr,
> StringLen, requiredSize, RInfo);
>
> Here is my D7 call (that doesn't work):
>        Status := ps5000aGetUnitInfo( ps5000a_handle, @MyReturnStr,
> StringLen, requiredSize, RInfo);
>
> In D7 I have to add "@" on "MyReturnStr or the program crashes.  With
> the "@" added the program doesn't crash, but things still don't work.
>
> Any suggestions on what to look at?

Sorry, but after I sent the email above I realized that I was editing a 
file in the wrong folder.  Free Pascal doesn't work with "var" on the 
line below:
   var str : Pchar;

This is what works on FPC 2.6.4:
function ps5000aGetUnitInfo
          (handle : smallInt;
           Str : Pchar;
           stringLength : smallInt;
           var requiredSize : smallInt;
           info : integer
           ) : integer;
{$IFDEF WIN32} stdcall; external 'ps5000a.dll';{$ENDIF}