Re: PostgreSQL C Language Extension with C++ Code

I did it with the macros

extern "C" {
Datum sum_of_numbers(PG_FUNCTION_ARGS);
PG_FUNCTION_INFO_V1(sum_of_numbers);
}

But now my compiler throws some other errors when running make:

g++ --std=c++17 -fPIC -Wall -Werror -g3 -O0 -o myfunc.o -c myfunc.cpp
-I/usr/pgsql-10/include/server -L"/usr/local/lib/libseal.a"
-I"/usr/local/include/seal" -I"/usr/local/include/cppcodec"
myfunc.cpp:29:10: error: conflicting declaration of C function ‘int64_t
sum_of_numbers()’
int64_t sum_of_numbers(){
^~~~~~~~~~~~~~
In file included from /usr/pgsql-10/include/server/utils/array.h:64,
from /usr/pgsql-10/include/server/utils/acl.h:38,
from
/usr/pgsql-10/include/server/catalog/objectaddress.h:18,
from
/usr/pgsql-10/include/server/catalog/pg_publication.h:21,
from /usr/pgsql-10/include/server/utils/rel.h:21,
from myfunc.cpp:3:
myfunc.cpp:25:21: note: previous declaration ‘Datum
sum_of_numbers(FunctionCallInfo)’
PG_FUNCTION_INFO_V1(sum_of_numbers);
^~~~~~~~~~~~~~
/usr/pgsql-10/include/server/fmgr.h:374:14: note: in definition of macro
‘PG_FUNCTION_INFO_V1’
extern Datum funcname(PG_FUNCTION_ARGS); \
^~~~~~~~
make: *** [Makefile:16: myfunc.o] Error 1

Why is it so hard to use C++ with PostgerSQL for a C extension? :)

Regards,
Tal

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