postgresql dynamic loading c functions

compile.sh

cc -fpic -c func.c -I`pg_config --includedir-server`
cc -shared -o func.so func.o
#mv func.so server dynamic lib directory
mv func.so `pg_config --pkglibdir`
cd `pg_config --pkglibdir`
chown root:root func.so

func.c

#include "postgres.h"
#include "fmgr.h"


#ifdef PG_MODULE_MAGIC
PG_MODULE_MAGIC;
#endif
// https://www.postgresql.org/docs/9.5/static/xfunc-c.html
PG_FUNCTION_INFO_V1(add_one);

Datum
add_one(PG_FUNCTION_ARGS)
{
    int32   arg = PG_GETARG_INT32(0);

    PG_RETURN_INT32(arg + 1);
}
//