Jump to content
  • Advertisement
Sign in to follow this  

c and c++

This topic is 4078 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

Hi guys, I have a program that uses a c and a c++ compiler and then links the results into one app. I know this isnt pretty but there is no way to prevent it in this app. Now my problem is that I want to pass a class from the c++ side to the c side. Since c doesnt have classes I am looking for a workaround. Is it maybe possible to have the c++ class inherit from a struct which declares the functions required and then pass a pointer to that struct? Any other ideas that are have way pretty? -CProgrammer

Share this post

Link to post
Share on other sites

On one end of the spectrum, you have a C interface which might look like this:

struct myclass;
typedef struct myclass myclassptr;

myclassptr CreateMyClass( ... );
void DestroyMyClass( myclassptr );
unsigned GetMyClassMember( myclassptr );

This is relatively easy -- you can define the structure on the C++ side of things only, and in C++, structures and classes are synonymous (with only effects on default access). The functions you can define inline to your C++ with `extern "C"`. The C API only interacts with myclass*, never myclass, so it doesn't even need to know the definition. This lets you use a non-POD myclass.

On the other hand, you may have a class which you need to store on the stack in your C code, involving virtual functions. In this case, you basically have to implement the class in C:

typedef struct myclass_vtable {
unsigned (*get_member)( myclassptr );
} *myclass_vtable_ptr;

struct myclass {
/* special */
myclass_vtable_ptr _vtable;

/* public */

/* private */
unsigned _a, _b;

unsigned GetMyClassMemberDefaultImpl( myclassptr self ) {
return self->_a + self->_b;

myclass_vtable default_vtable = {

void InitializeMyClass( myclassptr self ) {
self->_vtable = &default_vtable;
self->_a = 42;
self->_b = 24;

void CleanupMyClass( myclassptr self ) {
/* any cleanup code that might be necessary */

unsigned GetMyClassMember( myclassptr self ) {
return (*(self->_vtable->get_member))( self );

And no, you can't clean up the syntax for your C++ code without doing one of the following:
1) Invoking undefined behavior
2) Wrapping the entire thing

[Edited by - MaulingMonkey on May 23, 2007 10:28:39 AM]

Share this post

Link to post
Share on other sites
Sign in to follow this  

  • Advertisement

Important Information

By using GameDev.net, you agree to our community Guidelines, Terms of Use, and Privacy Policy.

We are the game development community.

Whether you are an indie, hobbyist, AAA developer, or just trying to learn, GameDev.net is the place for you to learn, share, and connect with the games industry. Learn more About Us or sign up!

Sign me up!