Re: [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}

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