CODEWITHSUNDEEP
c++linuxsqlite
The Unholy Metal Machine
The Unholy Metal Machine

Reputation: 1103

Sqlite3, I don't understand why my pointer is returned nulled

I'm writting a function to open a database, this is how it looks so far : 

bool
Sqlite3::openDB(std::string filename, sqlite3* db)
{
  std::ifstream file ( filename.c_str() );  
  if( !file )
  {
    std::cerr << "Can't open database, file not found. " << std::endl;
    return false;
  }
  file.close();

  if( sqlite3_open(filename.c_str(), &db) )
  {
    std::cerr << "Can't open database: " << sqlite3_errmsg(db) << std::endl;
    sqlite3_close(db);
    return false;
  }
std::cout << (int)db << std::endl; // added to check the pointer (3)
  return true;
}

in main() :

int main(int argc, char **argv)
{
  sqlite3 *db = nullptr;

  std::cout << (int)db << std::endl; // (1)

  // Open Database 
  sqlite3_engine.openDB("./bedrock.db",db);
  std::cout << (int)db << std::endl; // (2)

/*...*/

}

at (1) I get null, at (3) I get something not null but at (2) I get something null and I don't understand why...

Upvotes: 0

Views: 145

Answers (1)

laalto
laalto

Reputation: 152817

Function parameters are passed by value. openDB() gets a copy of the db variable, modifies the copy and prints it. The original variable is not modified.

If you want to modify the parameter, pass by reference (e.g. as sqlite3 *&).

Upvotes: 1

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