Bruno Haible <br...@clisp.org> writes:
> Hi Alex,
>
>> > Hello, I'm trying to use C++ in a project that uses Gnulib, and I need
>> > to use C linkage around a statement that eventually includes verify.h.
>> > However, this leads to the following error message:
>> >
>> > ./lib/verify.h:178:1: error: template with C linkage
>> > template <int w>
>
> You are supposed to do
> #include "verify.h"
> not
> extern "C" {
> #include "verify.h"
> }
>
> As far as I can see from
> https://isocpp.org/wiki/faq/mixing-c-and-cpp#include-c-hdrs-personal
> https://devzone.nordicsemi.com/f/nordic-q-a/2590/please-can-you-add-extern-c-as-appropriate-to-your-header-files
> the preferred way to include .h files in C++ is like
> #include "verify.h"
Right, my issue was that the file I need to include has to be wrapped in
an extern "C" because I need to have C linkage with the definitions
provided, but that file in turn includes verify.h.
I suppose now that I've found out that extern "C++" works, I could wrap
the particular include verify.h statements in extern "C++" instead of
having it in upstream. Perhaps an upstream fix would help someone out in
the future, but it's not important enough to include it if it's too much
trouble.
>> It figures that I found a way right after posting this; is the following
>> diff a good solution for upstream?
>
> Not really. We have enough work testing our .h files in 2 situations:
> - included from C
> - included from C++
> Making our .h file work in 3 situations
> - included from C
> - included from C++
> - included from C++ inside extern "C" {}
> makes for extra effort, with no real gain.
In this case the extern "C++" turns the 3rd situation into the 2nd
situation, and is a no-op in the 2nd situation, so I'm not sure this
would involve much extra effort. As said above, though, it's not a big
deal now.
Thanks for responding.
