Hi
I'm trying to link a Delphi lib against a C program. Indeed
the library has been done with Kylix and the program is compiled
with GCC but I think the problem concerns the linker/compiler
and is not specific to a platform.
Let's say I've a Delphi record declared like that :
type
TFooStruct = packed record
A: Integer;
B: PChar;
C: Char;
D: Int64;
E: Boolean;
F: Boolean;
G: Boolean;
H: Cardinal;
I: Byte;
end;
The library just displays the values of the record sent :
function Foo(S: TFooStruct): Boolean; cdecl;
begin
WriteLn('Valeur de A (Integer): ', S.A);
WriteLn('Valeur de B (PChar): ', S.B);
WriteLn('Valeur de C (Char): ', S.C);
WriteLn('Valeur de D (Int64): ', S.D);
WriteLn('Valeur de E (Boolean): ', BoolToStr(S.E, True));
WriteLn('Valeur de F (Boolean): ', BoolToStr(S.F, True));
WriteLn('Valeur de G (Boolean): ', BoolToStr(S.G, True));
WriteLn('Valeur de H (Cardinal): ', S.H);
WriteLn('Valeur de I (Byte): ', S.I);
Result := True;
end;
exports
Foo;
I translated the Kylix header file into C :
#ifndef __SOINTF__
#define __SOINTF__
struct TFooStruct {
int A ;
char * B ;
char C ;
long long D ;
int E ;
int F ;
int G ;
unsigned int H ;
unsigned char I ;
} ;
int Foo(struct TFooStruct S);
#endif
...and made foo.c which use it :
#include <stdio.h>
#include <stdlib.h>
#include "sointf.h"
int main(void) {
struct TFooStruct R;
R.A = 42;
R.B = "Haha";
R.C = '*';
R.D = 4242;
R.E = 0;
R.F = 1;
R.G = 0;
R.H = 1985;
R.I = 42;
Foo(R);
return EXIT_SUCCESS ;
}
Now, I compile and run the program :
gcc -L/home/astase/testso -lProject1 -o foo foo.c
./foo
Valeur de A (Integer): 42
Valeur de B (PChar): Haha
Valeur de C (Char): *
Valeur de D (Int64): 0
Valeur de E (Boolean): True
Valeur de F (Boolean): False
Valeur de G (Boolean): False
Valeur de H (Cardinal): 0
Valeur de I (Byte): 193
After having displayed the value of the "C" field (the char), it bugs. Read values are wrong from the Int64 field to the end.
Some points I would like to clarify :
- Should I declare my struct "packed" in Delphi ? It was my first
thought after reading Windows.pas (at lot of records are declared
packed)... But it doesn't seems to work !
- Should I change the compiler settings in my Delphi project ?
I think especially to the field alignment parameter, set to 8 by
default...
- Should I introduct some special directives like #pragma pack(X)
in the C side ?... I tested pragma pack() (C side) with packed
record (Object Pascal side), but it does not work...
In a nutshell, how can this Delphi struct be used in C ??
TIA
Best Regards
Adrien
