«

mattia wrote:
> I've see in some code:
>
> #ifdef __cplusplus
> extern "C"
> {
> #endif
>
> what does it mean?
>
> Thanks

Others have stated what it means; I'd just add that I've usually seen
this idiom used in system header files (such as stdio.h) so that the
same header can be used for both C and C++ compilers. C compilers (DS9K
excluded) don't define __cplusplus and don't see the extern "C" bit,
while C++ compilers do define it and so know that all the stdio.h
functions declared are C-style functions and linked in a C-style way.

I wouldn't recommend this practice in your own code.

extern "C" has no defined meaning in C. You'd probably get better
answers in comp.lang.c++.

Philip

Philip Potter <> writes:

> mattia wrote:
>> I've see in some code:
>>
>> #ifdef __cplusplus
>> extern "C"
>> {
>> #endif
>>
>> what does it mean?
>>
>> Thanks
>
> Others have stated what it means; I'd just add that I've usually seen
> this idiom used in system header files (such as stdio.h) so that the
> same header can be used for both C and C++ compilers. C compilers (DS9K
> excluded) don't define __cplusplus and don't see the extern "C" bit,
> while C++ compilers do define it and so know that all the stdio.h
> functions declared are C-style functions and linked in a C-style way.
>
> I wouldn't recommend this practice in your own code.
>
> extern "C" has no defined meaning in C. You'd probably get better
> answers in comp.lang.c++.
>
> Philip

The answer has been given exactly as is more than once. Traipsing over
there is slightly overkill IMO.

Richard wrote:
> Philip Potter <> writes:
>
>> mattia wrote:
>>> I've see in some code:
>>>
>>> #ifdef __cplusplus
>>> extern "C"
>>> {
>>> #endif
>>>
>>> what does it mean?
>>>
>>> Thanks
>> Others have stated what it means; I'd just add that I've usually seen
>> this idiom used in system header files (such as stdio.h) so that the
>> same header can be used for both C and C++ compilers. C compilers (DS9K
>> excluded) don't define __cplusplus and don't see the extern "C" bit,
>> while C++ compilers do define it and so know that all the stdio.h
>> functions declared are C-style functions and linked in a C-style way.
>>
>> I wouldn't recommend this practice in your own code.
>>
>> extern "C" has no defined meaning in C. You'd probably get better
>> answers in comp.lang.c++.
>>
>> Philip
>
> The answer has been given exactly as is more than once. Traipsing over
> there is slightly overkill IMO.

It's up to the OP. __cplusplus doesn't have much meaning in C, and
extern "C" even less, so if you want to be sure of your answers, you're
better asking a C++ expert.

Phil

Philip Potter <> writes:

> Richard wrote:
>> Philip Potter <> writes:
>>
>>> mattia wrote:
>>>> I've see in some code:
>>>>
>>>> #ifdef __cplusplus
>>>> extern "C"
>>>> {
>>>> #endif
>>>>
>>>> what does it mean?
>>>>
>>>> Thanks
>>> Others have stated what it means; I'd just add that I've usually seen
>>> this idiom used in system header files (such as stdio.h) so that the
>>> same header can be used for both C and C++ compilers. C compilers (DS9K
>>> excluded) don't define __cplusplus and don't see the extern "C" bit,
>>> while C++ compilers do define it and so know that all the stdio.h
>>> functions declared are C-style functions and linked in a C-style way.
>>>
>>> I wouldn't recommend this practice in your own code.
>>>
>>> extern "C" has no defined meaning in C. You'd probably get better
>>> answers in comp.lang.c++.
>>>
>>> Philip
>>
>> The answer has been given exactly as is more than once. Traipsing over
>> there is slightly overkill IMO.
>
> It's up to the OP. __cplusplus doesn't have much meaning in C, and
> extern "C" even less, so if you want to be sure of your answers, you're
> better asking a C++ expert.
>
> Phil

As I said - the answer was already posted many times. There are many
here who know both - and it is a "both" question since many C
programmers mix and match.

mattia wrote:
>
> I think that I'll note use __cplusplus unless I'll have to link my
> headers with cpp code. That will be my rule. Thanks all for the reply.
>
If you think there's the remotest chance your C library might be used
with C++, you may as well use the "extern C" wrappers. There's no
cost/impact to C code and you might save you or your users future work.

I always use "extern C" wrappers.

--
Ian Collins.