std::bad_alloc error while appending to QString

Ali Rashidi

Hi everyone and thanks for your care to this question.

I`m writing a class, that gets a base URL, and 2 QStringLists of parametr values and names, then appends them to the base url to make a working URL, send request and get reply.

The problem is, the program crashes whie appending to the finalURL. see this code:

void NetworkObject::makeURL()
{
    _finalURL.append(_baseURL);
    _finalURL.append("?");
    qDebug() << _finalURL.toLatin1();
    for (int i = 0; i < _varNameList.size(); i++)
    {
        _finalURL.append(_varNameList[i]);
        _finalURL.append("=");
        _finalURL.append(_varValueList[i]); //##
        if (i =! _varNameList.size() - 1)
        {
            _finalURL.append("&");
        }
    }
}

Using debugger, I found it occurs on the line marked with ##.

Something makes me amazed and that is, I made a mistake before, and instead of that if statement, just wrote:

_finalURL.append("&");

and it had no error in this scope.

mjsurette

@Ali-Rashidi
I would have

_finalURL = _baseURL;

as the first line. That way you're sure that you know _finalURL is not filled with results from previous calls. std::bad_alloc would suggest that you're running out of memory. These days that's pretty hard to do.

As an aside, did you consider using QStringList::join?

Mike

mrjj

Hi

The if looks wrong to me

if (i =! _varNameList.size() - 1)

I would expect

if ( i ! = _varNameList.size() - 1)

Also as Mike says, it sounds like out of memory but URLs are normally not that big.
Have you tried qDebug() << varNameList[i]; to see what u are appending?
(in the loop)

Ali Rashidi

@mrjj Oh I forgot that, however, I still faced SEGFAULT using this approach in another part, so changed the method completely, thanks for help