error: template with C linkage

[Marc Glisse]

On Sun, 18 Sep 2011, Jeffrey Walton wrote:

> On Sat, Sep 17, 2011 at 4:21 PM, Jonathan Wakely <jwakely.gcc@gmail.com> wrote:
>> On 17 September 2011 14:23, Jeffrey Walton wrote:
>>> /usr//include/cryptopp/cryptlib.h:99: error: template with C linkage
>> ...
>>> I've tried adding '-x c++' to force c++ in the files.
>>
>> That's obviously not going to help.
>>
>> If the compiler complains about a template, it's not compiling C,
>> because there's no such thing in C. Â Ditto for C linkage; everything
>> in C has C linkage, so there's no concept of any other kind of
>> language linkage, so no reason a C compiler would ever mention "C
>> linkage". Â So the compiler was already treating the files as
>> containing C++ (just apparently assuming that everything in a system
>> directory gets an implicit extern "C" around it.)
> OK, thanks. I'm not sure what the implications of "system compiler"
> are, but OpenBSD's configuration did not like those files in
> /usr/include.
>
> $ g++ -v
> Reading specs from /usr/bin/../lib/gcc-lib/i386-unknown-openbsd4.9/4.2.1/specs
> Target: i386-unknown-openbsd4.9
> Configured with: OpenBSD/i386 system compiler
> Thread model: posix
> gcc version 4.2.1 20070719
> $
>
> Do you have any ideas why a location would make a difference?

Antique platforms have system headers that don't know about C++, so g++ 
implicitly adds extern "C" around them. And being a system header is a 
property that depends on the directory the file is in.

-- 
Marc Glisse