Re: using C++ code in a C Pogram that can be compiled by gcc

[Eljay Love-Jensen <eljay at adobe dot com>]

Hi Ziad,

You have two choices.

1) compile/convert your C program into a C++ program.  This is my 
recommended course of action.

2) make a C API thunk layer to your C++ library.  This involves figuring 
out which functions you want to expose, and making a C thunk routine either 
in your C++ library itself, or in an ancilliary thunk C++ library, which 
uses 'extern "C" ...' declarations for the glue code which maps to the C++ 
routines.  The glue routine (aka thunk routines) also have to trap any 
exceptions that could be thown, and repackage them into something a C 
program could work with.

Option #1 is probably less effort, which is why I recommend it.

For option #2, you may wonder "I have a Foo object, and I need to access 
it's Bar method, how do I do that?"

The thunk  routine will look something like...
extern "C" int Foo_Bar(void* vfoo, int parm1, int parm2);
int Foo_Bar(void* vfoo, int parm1, int parm2)
{
  int err = 0;
  Foo* foo = static_cast<Foo*>(vfoo);
  try
  {
    foo->Bar(parm1, parm2);
  }
  catch(...)
  {
    err = 1;
  }
  return err;
}

HTH,
--Eljay