Problem compiling program with pqxx

Question

I'm trying to compile a very simple program (sample that does nothing) with pqxx, but cannot do it. Here's the 'program':

$ cat xx.cpp

#include <pqxx/pqxx>
using namespace pqxx;


int main() 
{
    connection conn("dbname=dout1");
    return 0;
}

The command I used to try to compile in C++:

g++ -I /usr/local/include/ -L /usr/local/lib/ -l pqxx -I /opt/postgres_home/include/ -L /opt/postgres_home/lib/ -lpq xx.cpp

Message returned:

/tmp/cc18wMEy.o: In function `pqxx::connect_direct::connect_direct(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)':
xx.cpp:(.text._ZN4pqxx14connect_directC1ERKSs[pqxx::connect_direct::connect_direct(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)]+0x1f): undefined reference to `pqxx::connectionpolicy::connectionpolicy(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)'
xx.cpp:(.text._ZN4pqxx14connect_directC1ERKSs[pqxx::connect_direct::connect_direct(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)]+0x2a): undefined reference to `vtable for pqxx::connect_direct'
/tmp/cc18wMEy.o: In function `pqxx::connect_direct::~connect_direct()':
xx.cpp:(.text._ZN4pqxx14connect_directD1Ev[pqxx::connect_direct::~connect_direct()]+0x13): undefined reference to `vtable for pqxx::connect_direct'
xx.cpp:(.text._ZN4pqxx14connect_directD1Ev[pqxx::connect_direct::~connect_direct()]+0x1f): undefined reference to `pqxx::connectionpolicy::~connectionpolicy()'
/tmp/cc18wMEy.o: In function `pqxx::basic_connection<pqxx::connect_direct>::basic_connection(char const*)':
xx.cpp:(.text._ZN4pqxx16basic_connectionINS_14connect_directEEC1EPKc[pqxx::basic_connection<pqxx::connect_direct>::basic_connection(char const*)]+0x2b): undefined reference to `pqxx::connection_base::connection_base(pqxx::connectionpolicy&)'
xx.cpp:(.text._ZN4pqxx16basic_connectionINS_14connect_directEEC1EPKc[pqxx::basic_connection<pqxx::connect_direct>::basic_connection(char const*)]+0xd6): undefined reference to `pqxx::connection_base::init()'
/tmp/cc18wMEy.o: In function `pqxx::basic_connection<pqxx::connect_direct>::~basic_connection()':
xx.cpp:(.text._ZN4pqxx16basic_connectionINS_14connect_directEED1Ev[pqxx::basic_connection<pqxx::connect_direct>::~basic_connection()]+0x17): undefined reference to `pqxx::connection_base::close()'
collect2: ld returned 1 exit status

If I do like:

$ g++ -I /usr/local/include/pqxx -L /usr/local/lib/ -l pqxx -l pq xx.cpp

Returns:

/usr/lib64/gcc/x86_64-slackware-linux/4.4.4/../../../../x86_64-slackware-linux/bin/ld: cannot find -lpq
collect2: ld returned 1 exit status

Considering:

$ cat /etc/ld.so.conf

/usr/local/lib
/usr/local/pgsql/lib                <-- just symlink to /opt/postgres_home/
/opt/postgres_home/lib
/usr/x86_64-slackware-linux/lib
/usr/lib64/seamonkey
/opt/kde3/lib64
/usr/lib64/jre1.6.0_16/lib/amd64

I really don't know what else to do, because:

 # ls /opt/postgres_home/lib/libpq*                                                      
/opt/postgres_home/lib/libpq.a     /opt/postgres_home/lib/libpq.so.5.3
/opt/postgres_home/lib/libpq.so    /opt/postgres_home/lib/libpqwalreceiver.so
/opt/postgres_home/lib/libpq.so.5

Luis

Mascarenas

Answer 1

After an email exchange with pqxx author Jeroen T. Vermeulen, I could manage to compile the 'program'. The idea was to place xx.cpp before -lpqxx -lpq So, the entire command is:

g++ -I /usr/local/include/pqxx/ -L /usr/local/lib/ -I /usr/local/pgsql/include/ -L /usr/local/pgsql/lib/ xx.cpp -lpqxx  -lpq

It works now.

Mascarenas

Even I get the undefined reference and in my case I'm using code::blocks. do you have a fix or some idea about it? – Frazee

What happens if you use g++? – Mascarenas

Answer 2

Works for me here with a simple g++ -lpqxx xx.cpp, so it terribly looks like a broken installation. Note that you don't need to link with libpq, as libpqxx with take care of that for you if you are using shared objects.

Check that you don't have the libpqxx library installed in different places, like /usr/lib, /usr/local, and /usr/local/pgsql/lib.

Medication

Thank you for your help, but the problem was not the one you mentioned. – Mascarenas

Answer 3

You do need to link to both libpqxx and libpq (in that order). You just don't need the libpq headers while compiling your own code.

In the original post, it's actually libpq that's missing. It's probably just in an unexpected location.

Seminarian