should I open QFile before size()

DungeonLords

I want to call

QFile file("1.txt");
auto mysize= file.size();

In fact this code works in my OS. But I am afraid of UB... Should I open file before ask size()?

DungeonLords

Solution:
"The documentation states that QFileDevice::size() returns the size of the file. If the function were to require an open file, its documentation would say that. By convention, Qt doesn't document non-requirements."

JonB

@DungeonLords
If it works without opening the file then I imagine it uses a call which has nothing to do with whether the file is open. I agree the docs are not clear on this. If you feel "unsure" about this behaviour, change to using qint64 QFileInfo::size() const, QFileInfo for sure just looks at OS file information without opening it.

Christian Ehrlicher

@JonB said in should I open QFile before size():

I agree the docs are not clear on this

All QFile (not QIODevice) functions are working without open() first. Don't think that this should really be documented.

DungeonLords

Solution:
"The documentation states that QFileDevice::size() returns the size of the file. If the function were to require an open file, its documentation would say that. By convention, Qt doesn't document non-requirements."