On 09/19/2011 02:19 PM, Ian Lance Taylor wrote:
Marc Glisse<marc.glisse@xxxxxxxx> writes:
On Sun, 18 Sep 2011, Jeffrey Walton wrote:
On Sat, Sep 17, 2011 at 4:21 PM, Jonathan Wakely<jwakely.gcc@xxxxxxxxx> 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. 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". 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.
This approach is controlled on a target-by-target basis, by the way. If
OpenBSD's header files are C++ ready, gcc's OpenBSD target configuration
should be changed to define NO_IMPLICIT_EXTERN_C.
Does '-isystem' factor into this in any way? I would hope that using
'-isystem' to specify an additional directory of 'system' header files
would not also turn on implicit 'extern "C"' mode.
If you are curious, we use '-isystem' to have GCC relax our
warning/error modes on header files that are nominally part of our
project but are installed into 'system' locations (like
/opt/<package>/include).
--
Kevin P. Fleming
Digium, Inc. | Director of Software Technologies
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445 Jan Davis Drive NW - Huntsville, AL 35806 - USA
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