C++ linkage error

[ggf]

I am porting a code which ran on HP unix to CentOS. It was a working code and compiled with gcc3.1.x and a c++ file and now I tried to compile with gcc3-3.4.6 and gcc4-4.2.4 also. But still I get this conflicts in declaration error as pasted below.

In file included from ../../../lol/ntk/nt_kslog.h:155,
from ../../../lol/ntk/nt_kernel.h:243,
from ../../../lol/ntk/nt_cp.h:110,
from ../../../soml/include/soml-afi-afu.h:131,
from ../../include/pcdb.h:58,
from ../../include/pcdb_addtypes.h:59,
from pcdb_addtypes.cc:94:

/opt/bcs/include/syslog.h:93: error: previous declaration of 'void syslog(int, const char*, ...)' with 'C++' linkage
/opt/bcs/include/syslog.h:93: error: conflicts with new declaration with 'C' linkage

I have the extern "C" included like this . But still I face the same problem . What Am I missing ??

#ifdef __cplusplus
extern "C" {
#endif

#include <syslog.h>
#include <stdarg.h>

#ifdef __cplusplus
}
#endif

Also , I work on Centos 5 box and it compiled without any issues on one machine and the same throws this error on other box with centos and both compilers.

Could anyone please help me , Where Am I going wrong ?

[PanGalactic]

Have you identified the source of the previous declaration? Is it defined somewhere in your source tree?

[iharrold]

Are you forward declaring and functions not necessarily declared in a header file but implemented in a c library?

Edit:

The linker is saying syslog is previously defined with the c++ then being redefined for c.

I.e. in the example here:
http://www.jbox.dk/sanos/source/include/syslog.h.html

The functional already has the extern symbols.

[vichor]

I once faced a problem that may have something to do with yours, but mine was during the linking process.

Functions using a variable argument list (the ... parameter which is using syslog) may generate undefined symbol errors during the link . GNU libraries define the variable argument list behavior as a set of macros (va_list, va_args, etc), while HP-UX libraries defines it as function calls (function va_list, etc). Be careful to include GNU header files, not HP-UX ones. Pay special attention to the -I parameter in the gcc file.

Returning to your problem and now linking with my previous explanation... have you checked you are using GNU header files?

regards
Victor

[moorecm]

I'm not sure if this helps or not, but when mixing C and C++ I always refer back to the two FAQs found here:
http://www2.research.att.com/~bs/bs_faq2.html#callC