PQescapeLiteral没有定义？

#include <iostream>
#include <libpq-fe.h>
#include <string.h>

using namespace std;

int main(){
    PGconn *db;
    char connstring[] = "dbname=TheInternet";
    db = PQconnectdb(connstring);
    char url[] = "http://www.goo'gle.com/";
    cout<<PQescapeLiteral(db, (const char *)url, (size_t) strlen(url))<<"n";
}

g++ PQescapeLiteral_test.cpp -lpq 

g++ PQescapeLiteral.cpp -I/usr/include/pgsql:/usr/include/pgsql/server:/usr/include/pgsql/server/libpq -lpq

PQescapeLiteral.cpp: In function ‘int main()’:
PQescapeLiteral.cpp:12: error: ‘PQescapeLiteral’ was not declared in this scope