Kanade's Delphi Stuff -- Tips & Tricks

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Tips and Tricks on Delphi

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Delphi Tips: Reusing C code

Tip 36: Calling C in OBJ files
(modified: 23 Aug 2000)

36: Calling C in OBJ files

Date added/modified: 23 Aug 2000
Look up the keyword "Obj files, calling" in Delphi help. If you try it, it doesn't work.
I found that it only works with C modules. Here is an example:
TESTC.C file

#include 

void _stdcall _export showAMessage(char *msg) {
  MessageBox(NULL, msg, "obj test", MB_OK);
}

PAS file code, partial

{$L testc.obj}
procedure showAMessage(s: pchar); stdcall; external;

procedure TForm1.Button1Click(Sender: TObject);
begin
  showAMessage(pchar('It worked!'));
end;
I added testc.c to a C++ builder project and compiled. Then, I used it in a Delphi 5 PAS file as above. It works!
But, if I make it into a testc.cpp module then it doesn't work even if I add extern "C" to the declaration.