extern c in cpp file`

extern c in cpp file`

[y2bismil]

Hi all,

I was wondering what the consequences were (if any) of declaring a function as
extern "C" in a header file, and then implementing it in a cpp module.  It seems
to compile file, but I was wondering if there are any unintended consequences?

Thanks,

Yamin

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Re: extern c in cpp file`

[Eljay Love-Jensen]

Hi Yamin,

The  consequences of declaring a function as extern "C" are...

1) the name will be mangled according to your platform's C mangling convention*.
2) I recall (and I may be mistaken) that such a function acts as a "C barrier", and thus exceptions do not propagate through such a function.

Merely specifying the header declaration (prototype) as an extern "C" is good enough for the translation unit's definition (implementation) to use the C specification.

HTH,
--Eljay

* some C mangling conventions (depending on platform)...

1) convert to uppercase (ala Pascal)
2) prefix a leading underscore
3) leave the identifier as given.

Re: extern c in cpp file`

[Nathan Sidwell]

Eljay Love-Jensen wrote:
> Hi Yamin,
> 
> The  consequences of declaring a function as extern "C" are...
> 
> 1) the name will be mangled according to your platform's C mangling convention*.
> 2) I recall (and I may be mistaken) that such a function acts as a "C barrier", and thus exceptions do not propagate through such a function.
you are mistaken. when compiled by a C++ compiler, you'll get all the C++
exception semantics. When compiled by a C compiler, you might or might not
get unwind info emitted (with gcc -fexceptions, you will IIRC).

nathan

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