[Interest] QFile::write(const QByteArray&) does not write, all data?

[alexander golks]

Am Thu, 17 May 2018 10:31:55 -0500
schrieb Roland Hughes <roland at logikalsolutions.com>:

> On 05/17/2018 09:11 AM, alexander golks wrote:
> >> my code was:
> >>    qint64 res = f.write(data);  
> > just for the curious ones:
> >
> > i have at least compiled 5.6.4 now, but i can not produce the error with my qt5core.
> > using 5.6.3 from qt, error exists. using mine, does not exist...
> >
> > getting the error code directly after the f.write(data) gives me error code 183:
> >    ERROR_ALREADY_EXISTS
> >      183 (0xB7)
> >      Cannot create a file when that file already exists.
> >
> > but i assume, that the error is not from the failing WriteFile call. or does it?
> > anyone with some more ideas?
> > e.g. on how to reproduce or test?  
> 
> One of the annoying safety features of Qt is that it won't overwrite a 
> file. You got that error when you tried to open the file for output and 
> you didn't check for the error. There was some test case long ago where 
> it was deemed a security risk for Qt to overwrite existing files. This 
> deviates from standard C/C++ where you can. Before opening an output 
> file you need to test for its existence then delete it. You can also 
> play games with opening the file for I/O and truncating, but, success is 
> file system dependent on that one.
> 

the QFile::write call returns with no error, i called GetLastError() after the QFile::write() and got 183.
the file is written up to ~30MB, and suddenly already exists?
i am pretty sure, the file doesn't exist prior the call.

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