Crash using a class using mysql lib with wxWidgets

Question

I've been stuck for a while on a problem and can't find a good solution.

I wrote a small class to use the c mysql lib on my project.

I use this class from an other class, the compilation goes well, but when i call it the software crash.

I believe that i'm doing something wrong but I can't find what. Maybe some advanced ppl will know.

Sql class:

class MySQL
{
public:
    MySQL();
    ~MySQL();

    bool  Query(wxString Qu, MYSQL_RES * result);
    unsigned int Insert(wxString Table);
    bool Update(wxString Table, unsigned int Id, wxString Data);
    bool Delete(wxString Table, unsigned int Id);
protected:
private:
    void Close(void);
    bool Open(void);
    MYSQL mysql;
};

Sql function:

bool  MySQL::Query(wxString Qu, MYSQL_RES * result)
{
   //Qu.mb_str()
   if (this->Open()) {
      if (!mysql_query(&mysql, "jkjl")) {  //<--- I've replaced the Qu var to be sure it wasn't the reason.
         if ((result = mysql_store_result(&mysql))) {
                this->Close();
         } 
         else {
                //throw wxString::Format(wxT("Error: %i, %s"),  mysql_errno(&mysql), mysql_error(&mysql));
                this->Close();
         }

       } 
       else {
            //throw wxString::Format(wxT("Error: %i, %s"),  mysql_errno(&mysql), mysql_error(&mysql));
            this->Close();
       }
    }
    return true;
}

My other class to access to:

bool cldataproject::Load(std::list<cldataproject*> list_dataproject)
{
    MySQL sql;
    MYSQL_RES *result = NULL;
    MYSQL_ROW row = NULL;
    unsigned int  pos;
    cldataproject * list_project;
    wxString req;
    req = wxT("SELECT idproject, idclient, name, comment,  created_by, created_at, modified_by, modified_at FROM project  WHERE isdel=0 ORDER BY name ASC;");
    if ((sql.Query(req, result)))  // <--- Crash
    {
......

Open function:

bool MySQL::Open(void)
{
    mysql_init(&mysql);
    mysql_options(&mysql,MYSQL_READ_DEFAULT_GROUP,"option");
    if(mysql_real_connect(&mysql,MYSQL_HOST,MYSQL_LOGIN,MYSQL_PASS,MYSQL_BASE,0,NULL,0))
    {
        return true;
    } 
    else {
        return false;
    }
}

Note: Outside the class, on my main window (wxwidgets) this is working without any problem:

 str = wxT("SELECT idclient, name,  created_by, created_at, modified_by, modified_at FROM client WHERE isdel=0 ORDER BY name ASC;");
        mysql_query(&mysql, str.mb_str());
        result = mysql_store_result(&mysql);

Update

The goal of the class was to simply use it from the wxWidgets parts without taking care of the convertion.

I have tried to separate but it doesn't seem that the problem is coming from the wxString .

Something really strange I haven't been able to understand is that if I call:

MySQL sql;
sql.Query(wxT("blabla"), NULL)

from the constructor of my wxFrame it doesn't crash. If I do the same on a function on the wxFrame class, itself called from its constructor, it crashes.

like:

constructor {
   Query
}

Ok

constructor {
 function()
}

fonction {
    Query
}

Crash

I'm really confused...

Answer 1

Why are you mixing wxStrings and MySQL? That doesn't seem like a good idea. I would highly suggest just using normal strings everywhere, and separate out the WxWidgets code and the MySQL code completely, so you can figure out what's going wrong properly.