C/C++ extern "C" Variable compilation Macro

Question

How do I test to see if I am linking in C++ or C using macros? Say I have code that should link as C in a C++ file, I would use extern "C"{//code here}which would make my code in a link as C . How would I set up my name.c file to work for both C and C++. Something like...

#ifdef C++//or other macro
extern "C"{
#endif

#ifdef C++
}
#endif

What is the proper macro to replace the "C++" I have above, and will it be cross platform? or how can I set it up to be cross platform?

Also, What is the significance of having to do the extern "C"{} for C code in a C++ file?

Any help is appreciated. Thanks in advance.

(also, if you have **two** questions, then post two separate questions. The answer to your second question is not only easily googleable [well, so is the first one], but it's quite lengthy.) — The Paramagnetic Croissant, Jul 05 '14 at 15:15
@user3477950 I will be sure to do that next time if I have a multi part question. — Alex Zywicki, Jul 05 '14 at 15:21
@user3477950 the answer is actually very short. *There is no such thing as C code in a C++ file*. — n. 1.8e9-where's-my-share m., Jul 05 '14 at 15:23
@n.m. Well, yeah, too bad a lot of people are trying to treat C as if it was a subset of C++... :'( — The Paramagnetic Croissant, Jul 05 '14 at 15:24
@n.m. When I said "C code in a C++ file" I meant code that should be linked as C rather than C++. I will edit to clarify. — Alex Zywicki, Jul 05 '14 at 15:26
@n.m. Yes there in theory is no such thing as C code in a C++ file but I would argue that there is such a things a "C compatible" code in a C++ file, meaning code from a .cpp file that if put into a .c file would compile and link without modification. Much like C++ being am extension of the C language allowing code written for a C compiler to function without major modification in a C++ environment just in reverse. — Alex Zywicki, Jul 05 '14 at 15:41
Why the heck is this voted down? It's a perfectly reasonable question! — Owl, Jul 19 '17 at 00:17

score 2 · Accepted Answer · edited May 23 '17 at 10:32

2

"What is the proper macro to replace the "C++""

It's #ifdef __cplusplus

#ifdef __cplusplus
extern "C"{
#endif

//.....

#ifdef __cplusplus
}
#endif

For "...What is the significance of having to do....?"

Read : In C++ source, what is the effect of extern “C”?

edited May 23 '17 at 10:32

Community

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answered Jul 05 '14 at 15:16

P0W

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@user3477950 **Its** _"What is the proper macro to replace the "C++""_ – P0W Jul 05 '14 at 15:22
That would be "It's", with an apostrophe inserted at position 2. – The Paramagnetic Croissant Jul 05 '14 at 15:23

C/C++ extern "C" Variable compilation Macro

1 Answers1