Debugging an issue with QFile::copy, below is the code;
@
bool copy(const QString& src, const QString& dst)
{
if (QFile::exists(dst))
{
// log dst file exists
return false;
}
else
{
QFile fileHandler(src);
if (!fileHandler.copy(dst))
{
// log src and dst path
// log fileHandler.errorString() and fileHandler.error()
// log QFile::exists(src) and QFile::exists(dst)
return false;
}
}
return true;
}
@

This problem has occurred once and we have not been able to reproduce it. Here is the sequence of events;

1. The destination file does not exists prior to copying
2. The QFile::copy method fails
3. The src and dst contain a correct file path
4. The QFile::errorstring returns "Unknown error" and QFile::error returns 0.
5. After the QFile::copy has failed, both src and dst file exists

This information is contradictory. The destination file is not present, copying fails but for some reason destination file is now present.

The errorstring is not very helpful. The QIODevice::errorString() returns "Unknown error" if the internal errorstring variable is empty (QIODevice is the base class of QFile). How can QFile::copy return false with either an empty errorstring or errorstring set to "Unknown error"?

One option would be that the filename variable inside QFile is empty, however the log proves that is not the case.