kearns@read.columbia.edu (Steve Kearns) (09/14/89)
Is it possible to link a C program with a C++ library? The only a priori problem I could see is that the c++ global constructors would not be properly inited. I would like to create a library that supports C users, but I would prefer to write it in C++. Yes? No? -steve (kearns@cs.columbia.edu)
filoj@pc.ecn.purdue.edu (Jeffrey J Filo) (09/14/89)
In article <6497@columbia.edu> kearns@cs.columbia.edu writes: > >Is it possible to link a C program with a C++ library? >The only a priori problem I could see is that the c++ global >constructors would not be properly inited. In my research in solid modeling, I have had success linking C++ routines with C and even FORTRAN code. The way I approach it is to write a number of C functions that "turn around" and call C++ methods. For example, if an class Curve has a method SelfIntersect the C calling function can be written as: int SelfIntersect( Curve A) { A->SelfIntersect(); } A collection of these functions can be written for the set of methods. This set of functions can be compiled into an interface library. The C and FORTRAN code calls these interface functions and accesses the C++ routines in this way. One problem is that C doesn't really know about C++ objects, but a work-around is to treat the object pointers as integers. This approach is commonly used when manipulating C structures within FORTRAN code. ------ Jeff Filo filoj@pc.ecn.purdue.edu
bright@Data-IO.COM (Walter Bright) (09/16/89)
In article <6497@columbia.edu> kearns@cs.columbia.edu writes: <Is it possible to link a C program with a C++ library? <The only a priori problem I could see is that the c++ global <constructors would not be properly inited. Other problems: 1. C++ function names will appear bizarre to a C program. 2. The C compiler may not support the C++ calling sequence. <I would like to create a library that supports C users, but I would <prefer to write it in C++. Yes? No? The best way is to enclose each C++ function that is to be callable from C with a C 'wrapper', as in: static int function(int a, double b) { // do C++ stuff } extern "C" int function_wrapper(int a, double b) { return function(a,b); } (This is the 2.0 way of doing things.) As far as how to call static constructors, that will vary from system to system, and so will require customization for each.
dlw@odi.com (Dan Weinreb) (09/16/89)
In article <6497@columbia.edu> kearns@read.columbia.edu (Steve Kearns) writes:
Is it possible to link a C program with a C++ library?
The only a priori problem I could see is that the c++ global
constructors would not be properly inited.
Yes, that's the main problem. One way around the problem is to
include a small C++ program that defines "main" and calls another
function, called something like "cmain", passing all the arguments.
Then the C program uses the name "cmain" where it would have used
"main", to define its top-level function. Then you use CC as the
linker. This is kludgey, of course, but it's simple and it works.
You probably also want to provide a header file that defines a bunch
of nice, readable names to expand into the mangled names produced
by cfront.