C ++：extern和inline函数

Question

I have a couple of files written in C, and I want them to be C++-compatible, so for my C headers I use;

#ifdef __cplusplus
extern "C" {
#endif

at the beginning of the file and of course

#ifdef __cplusplus
}
#endif

...at the end. But it seems to create problems with the 'inline' keyword. My solution is to simply remove the inline keyword for C++, but I guess it could have a bad effect on C++ programs (these functions are called gazillions of times).

Is there a better solution ?

Answer 1

If I understand correctly, I would do:

 #ifdef __cplusplus
 #define D_INLINE static
 extern "C" {
 #else
 #define D_INLINE inline
 #endif

And use the D_INLINE for the functions that I think should need inline. As delnan said, the compiler will optimize it anyway and the inline keyword is just a hint to the compiler that the programmer thinks that the compiler should inline the function. It doesn't force the compiler to inline the function.

Answer 2

Inline functions are expected to be multiply defined, so:

#ifdef __cplusplus
extern "C" {
#elif __STDC_VERSION__ >= 199901L
   /* do nothing, C99 supports inline */
#else
#  define inline static
#endif

Many C compilers have non-standard extensions to mark functions as inline, you could also define it as __attribute__((always_inline)) (if __GNUC__ is defined)

EDIT: For better and more complete advice, see: http://www.greenend.org.uk/rjk/2003/03/inline.html