Linking external libraries in C in Visual Studio Code-CodePudding

Good afternoon! I have a following program in C , in VS Code. The program reads all data from a table called student. I compile this program with the command g retrieveDataFromTable.cpp -I "C:\Program Files\MySQL\MySQL Server 8.0\include" -L "C:\Program Files\MySQL\MySQL Server 8.0\lib" -l mysql -o test, and it perfectly gets compiled. It's my first time that I use an external library in my programs. So, I watched some videos about how linking works, and how to add an external library to our program. Basically, in those videos they used Visual Studio or Codeblocks for adding libraries, but I'm using VS Code. Eventually, I managed to make the program work, but I have some questions. First one is about the way I include header file "mysql.h". I mean it does not look professional. If I were to run this program in other device, of course that would not make any sense. So would anybody like to help me out how I could make it better? My second question is that the program does terminate if I did not have libmysql.dll in my project folder. I'm guessing that it's because I do dynamic linking with the library (please, correct me if I'm wrong). So does anybody know about how I could link this particular library statically? In general, I would really appreciate if anyone would give me some piece of advice about how I could improve this program, and what I should learn to know about these kind of things. Thank you)

#include <iostream>
#include "C:/Program Files/MySQL/MySQL Server 8.0/include/mysql.h"

struct CONNECTION
{
    const char *server = "localhost";
    const char *user = "root";
    const char *password = "password";
    const char *database = "project";
};

MYSQL *connection_to_database(CONNECTION connection)
{
    MYSQL *newConnection = mysql_init(NULL);
    if (!newConnection)
    {
        std::cout << "Failed to create an object" << std::endl;
        std::cout << mysql_error(newConnection) << std::endl;
        exit(0);
    }
    if (!mysql_real_connect(newConnection, connection.server, connection.user,
                            connection.password, connection.database, 3306, NULL, 0))
    {
        std::cout << "Failed to connect to database:" << std::endl;
        std::cout << mysql_error(newConnection) << std::endl;
        exit(0);
    }
    return newConnection;
}

MYSQL_RES *execute_query(MYSQL *connection, const std::string query)
{
    if (mysql_query(connection, query.c_str()))
    {
        std::cout << "MYSQL query error:\n"
                  << mysql_error(connection) << std::endl;
        exit(0);
    }
    return mysql_store_result(connection);
}

int main()
{
    CONNECTION id;
    MYSQL* connection = connection_to_database(id);
    MYSQL_RES* res = execute_query(connection, "SELECT * FROM students");
    
    int rows = mysql_affected_rows(connection);
    std::cout << rows << " rows were affected" << std::endl;

    int columns = mysql_num_fields(res);
    std::cout << columns << " columns in the table" << std::endl;

    MYSQL_ROW row;
    while((row = mysql_fetch_row(res)))
    {
        for (int i = 0; i < columns; i  ){
            std::cout << row[i] << " ";
        }
        std::cin.get();
    }

    return 0;
}

I looked some questions but I could not find something useful.

CodePudding user response：

How about using CMake? You can easily link external libraries into your target executable.

On top of that, is it perfectly supported on vscode by CMake tools extension.

CodePudding user response：

Thank you guys for your answers! I managed to solve this problem, but I need to do some research why it actually worked (if you could help me I would really appreciate it). Basically I made three directories: build, include, lib. "include" and "lib" directories I copied from MYSQL Server 8.0 directory. The outputs of cmake are stored in "build" directory. I have the following command in CMakeLists.txt:

cmake_minimum_required(VERSION 3.25)

project(myProject)

include_directories(${CMAKE_SOURCE_DIR}/include)

link_directories(${CMAKE_SOURCE_DIR}/lib)

add_executable(${PROJECT_NAME} main.cpp)

target_link_libraries(${PROJECT_NAME} mysql)

And it builds successfully. HOWEVER (!!!) when I try to run it, it just terminates. So I put libmysql.dll in "build" directory and then it ran. I'm really new to these things guys, and this solution of mine probably is not professional. If you guys could recommend me how to improve this procedure, or how to manage to make the program work without libmysql.dll file, I would really appreciate it.