[sane-devel] sane.h misses extern "C"

[Olaf Meeuwissen]

Rene Rebe <rene@rocklinux-consulting.de> writes:

> Hi,
>
> On: Mon, 12 Jul 2004 20:17:27 +0200,
>     Mattias Ellert <mattias.ellert@tsl.uu.se> wrote:
>
>> >>Is there a good reason why the installed sane.h misses the usual
>> >>header lines needed for compilation with C++?
>> > 
>> > Well, it's a C and not a C++ header and these #ifdefs are ugly :-)
>> 
>> If you put them in the header file you only need them once. Since they 
>> are not in the header files you have to do
>> 
>> extern "C" {
>> #include <sane/sane.h>
>> }
>> 
>> in every c++ file. I think this is more "ugly". Having the extern 
>> declaration in one single place (i.e. in the header file) makes so much 
>> more sense than having to put in in every single file where you include it.
>> 
>> You don't have to do this kind of hack for normal system header files. 
>> Almost all other header files have the extern "C" declaration (or the 
>> equivalent __BEGIN_DECLS __END_DECLS pair).
>
> Yes - ack. This is the way nearly any other system header is prepared ...
>
>> > Isn't it a better solution to use the extern "C" when including the
>> > file in the C++ .C code if you really want to use sane.h in C++? Or do
>> > we get trouble this way because it includes the structs?
>> 
>> I think having them in the header file is "the better solution".
>
> Sure - I just quick fixed it in my example app by doing so ... But I
> just wanted to note it publicly that we miss it ...
>
> I fully agree that C/C++ users assume including "some random" header
> will just work.
>
> I can only imagine one drawback - that current C++ projects (kooka)
> that include the "defect" header that have a private fix by
> surrounding the inclusion with the extern "C" declaration could
> fail. But at least with gcc 3.4.1 this is not the case - just tested
> it (I guess the old ones accept it, too).

Nested extern "C" declarations work with at least gcc 3.2 and later.
I do seem to recall that it also works with 2.97 but that's just a
vague recollection.

>> >>May I just commit them to CVS?
>> 
>> I would say YES.
>
> Any other votes ,-)? 

Please commit.
-- 
Olaf Meeuwissen                            EPSON KOWA Corporation, PF1
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