Re: C/C++

"Old Wolf" <>
6 Jul 2006 17:50:54 -0700
Frederick Gotham wrote:

jacob navia posted:

You can use any C function in C++ by qualifying it as extern "C", and
that is it, you can use it as you want!

Not quite "any"; the function declaration must still be correct
C++ code, e.g. this is no good:

  extern "C" int new(int delete);

and I think it mustn't have the same name as any overloaded C++
function in the same module (due to name mangling requirements).

Also, the function body must conform to a C ABI that the C++
compiler knows about.

Must every C++ compiler provide a facility for compiling C code?

No, but I don't know of any that don't.

Can the following program be considered universally portable?

/* stuff.c */

#include <stddef.h>
#include <stdlib.h>

char *AllocCharArray( size_t const len )
    return malloc(len);

/* main.cpp */

#include <cstdlib>

extern "C" { char *AllocCharArray( std::size_t const len ); }

Note, the braces are unnecessary.

int main()
    char * const p = AllocCharArray(64);


I guess it is a semantic issue about the word "portable". If you're
happy for it to include "portable to systems with both a C++
compiler and a compatible C compiler" , then yes. Note that
there are other practical issues too; the two compilers must
also be configured to link gainst the same runtime library.

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