在C＃pt中调试DLLImport。 2

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.