How to use a C lib in a C++ project

[BrownB]

Hello, I wrote a library to implement a communication protocol between a PalmOS palmtop ( programmed in C ) and a WinXP PC ( MSVC++ ). I need to implement the Hardware Abstraction Layer for the PC and the Palm. I used standard C programming for the lib, so the implementation of the HAL for the palm is ok.

But now I need to implement it for the PC program, which is a c++ project: must I modify the library functions using different calling conventions? In which way?

Also, I'd like to use MFC in the HAL implementation for PC: this involves to use a cpp compiler for the lib. Is this possible?

Thanks for help,
BrownB

[master5001]

Wait, what calling convention is used for the library functions? It sounds to me like you should be able to port this over directly as both c and c++ use the C calling convention.

[BrownB]

I spent some time looking around: now everything is clear enough, and the previous question is wrong: the problem wasn't the calling convention ( which is the same as you said ) but the file extension..must be cpp!

[misplaced]

i believe you use

extern "C" void myFunction(int, char);

this will compile the function as C functions.....C++ encode it's function names, C does not (or does not do it the same)...however, i've never done this myself so i could be way off....

i'm sure there is something in the FAQ about this though

[master5001]

Excellent. Your headers should look something like this (hint: name mangling):

Example

#ifndef MY_HEADER_FILE
#define MY_HEADER_FILE 1

#ifdef __cplusplus
extern "C" {   // c++ compile
#endif

/* 
 *  Insert your header info here.
 */

#ifdef __cplusplus
}              // c++ compile
#endif

#endif

[master5001]

I do recommend doing it more like my way as it allows the same header file to be compilable on both sides of your project. The C compiler will freak out when it sees extern "C".

[misplaced]

listen to master, s/he seems to know more than i do

[master5001]

Well lets not get carried away here. You can do as MS does and do what misplaced suggested.

Example

#ifdef __cplusplus
# define EXTERN_C extern "C"
#else
# define EXTERN_C
#endif

EXTERN_C void myFunction(int, char);

The above will compile using either C or C++ fine, and in both cases use C name mangling. The one major advantage to extern "C" { } is that you can basically copy/paste 6 lines of code into any existing header to make it C++ friendly.

[BrownB]

All good points, thanks!

See you!
BrownB

[master5001]

Yeah no problem. I'm also willing to bet this is on the FAQ, if not it couldn't hurt.