c++ std::vector<int> Undefined symbols for architecture x86_64: - c++

Question

I'm having problems using std::vector<int> in C++ on Mac OSX Catalina. I have a function static int insertMoneyData(std::vector<int> money) that writes data to an SQLite database. The function is declared in SQLFunctions.h and defined in SQLFunctions.cc.
When also running the function from SQLFunctions.cc, everything works fine in the compilation (using c++ in make). But when I try to run the same function from another file (city.cc), I get the following error:
Undefined symbols for architecture x86_64:
"insertMoneyData(std::__1::vector<int, std::__1::allocator<int> >)", referenced from:
City::save_money_data() in city.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1
(use -v to see invocation)
make: *** [main] Error 1
Calling insertMoneyData(money_data) from SQLFunctions.cc, where it is defined, works fine.
//SQLFunctions.cc
#include <iostream>
#include <sqlite3.h>
#include <stdio.h>
#include <vector>
#include <cstring>
#include "SQLfunctions.h"
using namespace std;
using Record = std::vector<std::string>;
using Records = std::vector<Record>;
int initiateDB() {
std::vector<int> money_data;
money_data.push_back(1);
money_data.push_back(2);
money_data.push_back(3);
money_data.push_back(4);
money_data.push_back(5);
money_data.push_back(6);
money_data.push_back(7);
money_data.push_back(8);
money_data.push_back(9);
money_data.push_back(10);
money_data.push_back(11);
money_data.push_back(12);
money_data.push_back(13);
insertMoneyData(money_data);
}
static int insertMoneyData(std::vector<int> money) {
const char* dir = "/Users/bennyjohansson/Projects/ekosim/myDB/ekosimDB.db";
sqlite3* DB;
char* messageerror;
int exit = sqlite3_open(dir, &DB);
string sql = "INSERT INTO MONEY_DATA (TIME, BANK_CAPITAL, BANK_LOANS, BANK_DEPOSITS, BANK_LIQUIDITY, CONSUMER_CAPITAL, CONSUMER_DEPOSITS, CONSUMER_DEBTS, COMPANY_DEBTS, COMPANY_CAPITAL, MARKET_CAPITAL, CITY_CAPITAL, TOTAL_CAPITAL) VALUES(";
sql.append(std::to_string(money[0]) + ", ");
sql.append(std::to_string(money[1]) + ", ");
sql.append(std::to_string(money[2]) + ", ");
sql.append(std::to_string(money[3]) + ", ");
sql.append(std::to_string(money[4]) + ", ");
sql.append(std::to_string(money[5]) + ", ");
sql.append(std::to_string(money[6]) + ", ");
sql.append(std::to_string(money[7]) + ", ");
sql.append(std::to_string(money[8]) + ", ");
sql.append(std::to_string(money[9]) + ", ");
sql.append(std::to_string(money[10]) + ", ");
sql.append(std::to_string(money[11]) + ", ");
sql.append(std::to_string(money[12]) + ");");
exit = sqlite3_exec(DB, sql.c_str(), NULL, 0, &messageerror);
}
However, when I call the function from another file, it doesn't work:
//City.cc
#include <iostream>
#include <iomanip>
#include <stdio.h>
#include <cstring>
#include <vector>
#include <list>
#include <fstream>
#include <cmath>
#include <random>
#include "SQLfunctions.h"
using namespace std;
void City::save_money_data() {
std::vector<int> money_data;
money_data.push_back(1);
money_data.push_back(2);
money_data.push_back(3);
money_data.push_back(4);
money_data.push_back(5);
money_data.push_back(6);
money_data.push_back(7);
money_data.push_back(8);
money_data.push_back(9);
money_data.push_back(10);
money_data.push_back(11);
money_data.push_back(12);
money_data.push_back(13);
insertMoneyData(money_data);
}
Declaring:
//SQLFunctions.h
#ifndef SQL_FUNCTIONS_H
#define SQL_FUNCTIONS_H
#include <iostream>
#include <sqlite3.h>
#include <stdio.h>
using namespace std;
using Record = std::vector<std::string>;
using Records = std::vector<Record>;
int initiateDB();
static int createDB(const char* s);
static int createParameterTable(const char* s);
static int createDataTable(const char* s);
static int createMoneyTable(const char* s);
static int insertParameterData(const char* s);
static int insertMoneyData(std::vector<int> money); //
static int updateData(const char* s);
static int updateParameter(const char* s, string, double);
static int deleteTheData(const char* s);
static int selectData(const char* s);
static int callback(void* NotUsed, int argc, char** argv, char** azColName);
int select_callback(void *p_data, int num_fields, char **p_fields, char **p_col_names);
Records select_stmt(const char* stmt, const char* s);
#endif

Answer 1

Problem is obsolete keyword static before each function.
static keyword has multiple meanings. In this context it means: this function definition should be visible only in this translation unit (translation unit means sources compiled during single compilation - so source file with all its includes).
So you defined a function which should be accessed by other translation units (other sources), but you have limited its visibility to single file where it is defined. That is why linker complains that can't find this functions.