無法編譯測試PostgreSQL程序

Question

當我在C++中編譯我的PostgreSQL程序時，出現這些錯誤。誰能告訴我這個原因。

user@linux-yyzo:~/WorkDir/Program> g++ test.cpp -lpqxx -I/usr/local/include -I/usr/local/pgsql/include 

/usr/local/lib/libpqxx.a(util.o): In function `pqxx::describe_thread_safety()': 
/home/user/WorkDir/Program/Connections/libpqxx-4.0/src/util.cxx:69: undefined reference to `PQisthreadsafe' 
/usr/local/lib/libpqxx.a(util.o): In function `pqxx::internal::freepqmem(void const*)': 
/home/user/WorkDir/Program/Connections/libpqxx-4.0/src/util.cxx:195: undefined reference to `PQfreemem' 
/usr/local/lib/libpqxx.a(result.o): In function `pqxx::internal::result_data::~result_data()': 
/home/user/WorkDir/Program/Connections/libpqxx-4.0/src/result.cxx:55: undefined reference to `PQclear' 
/usr/local/lib/libpqxx.a(result.o): In function `pqxx::result::size() const': 
/home/user/WorkDir/Program/Connections/libpqxx-4.0/src/result.cxx:101: undefined reference to `PQntuples' 
/usr/local/lib/libpqxx.a(result.o): In function `pqxx::result::empty() const': 
/home/user/WorkDir/Program/Connections/libpqxx-4.0/src/result.cxx:107: undefined reference to `PQntuples' 
/usr/local/lib/libpqxx.a(result.o): In function `pqxx::result::CmdStatus() const': 
/home/user/WorkDir/Program/Connections/libpqxx-4.0/src/result.cxx:241: undefined reference to `PQcmdStatus' 
/usr/local/lib/libpqxx.a(result.o): In function `pqxx::result::inserted_oid() const': 
/home/user/WorkDir/Program/Connections/libpqxx-4.0/src/result.cxx:256: undefined reference to `PQoidValue' 
/usr/local/lib/libpqxx.a(result.o): In function `pqxx::result::affected_rows() const': 
/home/user/WorkDir/Program/Connections/libpqxx-4.0/src/result.cxx:262: undefined reference to `PQcmdTuples' 
/usr/local/lib/libpqxx.a(result.o): In function `pqxx::result::GetIsNull(unsigned long, unsigned int) const': 
/home/user/WorkDir/Program/Connections/libpqxx-4.0/src/result.cxx:279: undefined reference to `PQgetisnull' 
/usr/local/lib/libpqxx.a(result.o): In function `pqxx::result::GetLength(unsigned long, unsigned int) const': 
/home/user/WorkDir/Program/Connections/libpqxx-4.0/src/result.cxx:286: undefined reference to `PQgetlength' 
/usr/local/lib/libpqxx.a(result.o): In function `pqxx::result::errorposition() const': 
/home/user/WorkDir/Program/Connections/libpqxx-4.0/src/result.cxx:344: undefined reference to `PQresultErrorField' 
/usr/local/lib/libpqxx.a(result.o): In function `pqxx::result::ThrowSQLError(std::string const&, std::string const&) const': 
/home/user/WorkDir/Program/Connections/libpqxx-4.0/src/result.cxx:132: undefined reference to `PQresultErrorField' 
/usr/local/lib/libpqxx.a(result.o): In function `pqxx::result::columns() const': 
/home/user/WorkDir/Program/Connections/libpqxx-4.0/src/result.cxx:363: undefined reference to `PQnfields' 
/usr/local/lib/libpqxx.a(result.o): In function `pqxx::result::column_name(unsigned int) const': 
/home/user/WorkDir/Program/Connections/libpqxx-4.0/src/result.cxx:353: undefined reference to `PQfname' 
/usr/local/lib/libpqxx.a(result.o): In function `pqxx::result::table_column(unsigned int) const': 
/home/user/WorkDir/Program/Connections/libpqxx-4.0/src/result.cxx:318: undefined reference to `PQftablecol' 
/usr/local/lib/libpqxx.a(result.o): In function `pqxx::result::StatusError() const': 
/home/user/WorkDir/Program/Connections/libpqxx-4.0/src/result.cxx:214: undefined reference to `PQresultStatus' 
/home/user/WorkDir/Program/Connections/libpqxx-4.0/src/result.cxx:233: undefined reference to `PQresultStatus' 
/home/user/WorkDir/Program/Connections/libpqxx-4.0/src/result.cxx:228: undefined reference to `PQresultErrorMessage' 
/usr/local/lib/libpqxx.a(result.o): In function `pqxx::result::column_table(unsigned int) const': 
/home/user/WorkDir/Program/Connections/libpqxx-4.0/src/result.cxx:303: undefined reference to `PQftable' 
/usr/local/lib/libpqxx.a(result.o): In function `pqxx::result::column_type(unsigned int) const': 

/usr/local/lib/libpqxx.a(connection.o): In function `pqxx::connect_direct::do_startconnect(pg_conn*)': 
/home/user/WorkDir/Program/Connections/libpqxx-4.0/src/connection.cxx:94: undefined reference to `PQstatus' 
/home/user/WorkDir/Program/Connections/libpqxx-4.0/src/connection.cxx:96: undefined reference to `PQerrorMessage' 
/usr/local/lib/libpqxx.a(tuple.o): In function `pqxx::result::column_number(char const*) const': 
/home/user/WorkDir/Program/Connections/libpqxx-4.0/src/tuple.cxx:194: undefined reference to `PQfnumber' 
collect2: error: ld returned 1 exit status 

Answer 1

您需要添加-lpq作爲一個選項，GCC到libpq本身聯繫起來。它有-lpqxx後去：

g++ test.cpp -lpqxx -lpq -I/usr/local/include -I/usr/local/pgsql/include 
#     ^^^^ here 

這是需要爲libpqxx只是周圍的libpq C接口這是PostgreSQL的真實客戶機庫中的C++包裝。如果在系統的庫路徑中找不到，您可能需要在-lpq之前添加-L/path/to/libpq。