Question

I am using the MySQL Embedded Library and using P/Invoke to call the necessary functions to start the server. We resolved some issues regarding it in this topic, however another issue has presented itself.

The mysql_server_init() function returns 0 if success, 1 if error. Unfortunately, in my code when it returns 1, and I use Marshal.GetLastWin32Error() the error code is 0. I am assuming that it is not picking up on the error being generated by mysql_server_init(), but I am at a loss as to how to find out where the problem is.

Here is the relevant code block…

    [DllImportAttribute("libmysqld.dll", SetLastError = true)]
    static extern int mysql_server_init(int argc, string[] argv, string[] groups);

    static string[] server_options = new string[2];
    static string[] server_groups = new string[3];

    public static bool Start()
    {
        server_options[0] = "mysql_test"; // not used?
        server_options[1] = "--defaults-file=./my.ini";

        server_groups[0] = "client";
        server_groups[1] = "server";
        server_groups[2] = "\0";

        if (mysql_server_init(2, server_options, server_groups) != 0)
        {
            int lastError = Marshal.GetLastWin32Error();
            Console.WriteLine("MySQL Library Init Failed with error code: " + lastError);
            return false;
        }

        Console.WriteLine("MySQL Library Started Successfully!");
        return true;
    }

Answer 1

The mysql_server_init function does not report errors via the Win32 error reporting mechanism SetLastError() and GetLastError(). So, you can”t use Marshal.GetLastWin32Error() to obtain the last error. The embedded mysql database reports errors via the functions mysql_error() and mysql_errno(). However, those functions seem to only report errors AFTER a successful call to mysql_server_init().

I think the problem of your code lies in the way you terminate your server_groups array.
You should use “null” instead of “\0” to “terminate” your array:

public static bool Start() 
{ 
    server_options[0] = "mysql_test"; // not used? 
    server_options[1] = "--defaults-file=./my.ini"; 

    server_groups[0] = "client"; 
    server_groups[1] = "server"; 
    server_groups[2] = null; 

    if (mysql_server_init(2, server_options, server_groups) != 0) 
    { 
        int lastError = Marshal.GetLastWin32Error(); 
        Console.WriteLine("MySQL Library Init Failed with error code: " + lastError); 
        return false; 
    } 
}

Errors regarding your configuration should be printed to the console window by the mysql_server_init() function.

Hope, this helps.