Query in C

Query in C

[avinash pawar]

Hello Everyone ,

   Can anyone of you please tell me..

       what does extern "C" int func(int *,foo) accomplish ?

   waiting for your reply.

regards,
Avinash

Re: Query in C

[Steve Graegert]

On 8/1/05, avinash pawar <lkmails@gmail.com> wrote:
> Hello Everyone ,
> 
>   Can anyone of you please tell me..
> 
>       what does extern "C" int func(int *,foo) accomplish ?
> 

When using existing C headers that already conform to ANSI C in C++
they need to be slightly modified to enable proper linkage for the
language and to ensure that C++ keywords are not used as identifiers.

This means that you can use C headers in C++ projects in the following way:

#ifdef __cplusplus
       extern "C" {
#endif
...
int func(int *,foo);
...
#ifdef __cplusplus
       }
#endif

Code placed between the two ifdefs is either linked as C or C++.  The
__cplusplus macro is usually predefined in appropriate system headers.

To answer your question: when a routine will be called from another
language (here C is called from C++) it should be declared in C++ as

extern "C" int func(int *,foo);

The extern "C" causes the routine to have a so called 'unmangled' name
that can be refered to not only from C but also from Fortran or Cobol.
 Without extern "C" the routine will get a link 'mangled' link name
like func__abc.

Regards

        \Steve

-- 

Steve Graegert
Software Consultancy
Mobile: +49 (176)  21248869   
Office: +49 (9131) 7126409

Re: Query in C

[r_zaca]

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  Hello Avinash, 

  This is a function that returns a "int value" and allows you to pass as 
parameters two data types, an "int pointer" and a "foo data". 
  Well, I think it would be helpful. 
  That's it. 


>Hello Everyone , 
> 
>   Can anyone of you please tell me.. 
> 
>       what does extern "C" int func(int *,foo) accomplish ? 
> 
>   waiting for your reply. 
> 
>regards, 
>Avinash