Re: [Patch 4.6] In system.h, wrap include of C++ header in 'extern C++'

[Gabriel Dos Reis <gdr at integrable-solutions dot net>]

On Fri, Jun 15, 2012 at 11:06 AM, Ian Lance Taylor <iant@google.com> wrote:
> Richard Guenther <richard.guenther@gmail.com> writes:
>
>> Ian - you added this include in rev. 167764, I don't think that was "proper".
>> But I'm not sure wrapping a system.h include inside extern "C" from a C++
>> plugin is proper either ...
>
> I did commit 167764 but I didn't write it. ?It's from
>
> http://gcc.gnu.org/ml/gcc-patches/2010-11/msg02567.html
> http://gcc.gnu.org/PR46650
>
> The patch is there because system.h poisons strerror. ?Clearly we have
> to #include <string.h> before poisoning strerror. ?And we do. ?But when
> we #include C++ headers, some of the C++ headers #include <cstring>. ?So
> system.h needs to do that also.
>
> I think there is no question that as long as system.h poisons strerror,
> we need to arrange to #include both <string.h> and <cstring> before that
> poisoning, and that the natural way to ensure that is to #include both
> in <system.h>. ?And that is what we do today.
>
> I don't really know what the right solution is here, because I don't
> know how we feel about wrapping #include "system.h" in extern "C". ?A
> simple workaround is to #include <cstring> before the #include
> "system.h". ?Or the OP's patch using extern "C++" is a simple workaround
> within system.h.
>
> Or maybe we simply drop the poison of strerror, and then system.h
> doesn't need to #include <cstring> anyhow.

As long as we don't control <string.h> and <cstring>, we can't put them
in a language linkage specification.  What we can do is what I suggested
in my last message: just give the language specification to the declarations
that matter in gcc/system.h.

-- Gaby