I have to interface to a DLL created in Delphi and I am running into all
types of problems.

For example ..

1) How is a delphi array organized ?

If I have a function in delphi ..

procedure SayIt3( N : array of integer ); stdcall;
var
  I : integer;
begin
  Writeln('Hello from SayIt3');
  Writeln('Array High Is ', High(N));
  for I := 0 to High(N) do
    begin
      Writeln(I,' => ',N[I]);
    end;
end;

and in "C" I have

typedef void (_stdcall *FP_SAYIT3) (int *);
FP_SAYIT3    sayit3 = ( FP_SAYIT3 ) GetProcAddress( hinst, "SayIt3" );
int ia[10] = { 3,1,2,3,4,5,6,7,8,9 };
(*sayit3)(ia);

The output is

Hello from SayIt3
Array High Is 3
0 => 3
1 => 1
2 => 2
3 => 3

I assume ia[0] is used as the array length indicator .. .. but in that case
how come ia[0] can be accessed from delphi as a regular element ?.

2) I know that delphi shortstring values are byte arrays where the first
byte indicates the length, and for the most part passing the value to/from
delphi is fine unless the delphi parameter is marked as "var" in which case
I run into a problem because the delphi routine is poping 4 bytes too many
off the stack when it returns.

ie  This routine works fine as far as cleaning up the stack ...

procedure SayIt(  N : shortstring ); stdcall;
begin
writeln('Hello from SayIt');
writeln(N);
N := 'Goodbye';
end;

but this routine causes 4 bytes too many to be popped off on the "ret"
instruction (its doing a "ret 8" instead of a "ret 4") .. it's almost as if
there is some hidden parameter due to the "var" .. but if I use "integer"
instead of "shortstring" then both versions ( with & without "var" ) do a
"ret 4".

procedure SayIt(  var N : shortstring ); stdcall;
begin
writeln('Hello from SayIt');
writeln(N);
N := 'Goodbye';
end;

for both versions I using the following in "C"

typedef void (_stdcall *FP_SAYIT)(void *);
FP_SAYIT     sayit  = (FP_SAYIT) GetProcAddress( hinst, "SayIt" );

char    p[256];

strcpy( &(p[1]),"Hello David..." );
p[0] = (char) strlen(&p[1]);
(*sayit)(p);
printf("Result = %d,%s\n", (int)(p[0]), &(p[1]));

Actually, I should also mention that for the routine from question #1, in
regard to the "array of integer", it too has the problem of popping an extra
4 bytes off the stack .. and in that case it happens irregardless of whether
the parameter is "var" or not.

Any Help is most appreciated ...

Thanks .. Dave

well this won't answer your questions but it might be of use in your
case :

I would advise you not to use arrays as parameters in your dll, use
pointers instead (integer^, or PChar )

For the stdcall, you better use cdecl, which is a C call covention. Of
course you can compile your C/C++ app as stdcall too, but is seems a
little bit tricky to me (you will have to define all functions as
stdcall ...).

well, hoping that this might help ...

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