[Interest] Strange undeletable QTemporaryFile. Is it a bug?

Alex Malyushytskyy alexmalvtk at gmail.com
Tue Aug 27 00:36:14 CEST 2013

Making function which were public in the parent, private in the child shows
that function should not be called.
That is it.  And that is the case.
It does not make it impossible to shoot yourself at the feet (whatever way
you choose)  and access it.
You can do everything in C++.

But if you do it, it is your problem and responsibility and you do not feel
frustrated cause the behavior does not meet your expectations.
QTemporaryFile::close () is not meant to be public. User have no use of it.
Make it private and this question will not ever rise again.

On Sun, Aug 25, 2013 at 4:02 AM, Constantin Makshin <cmakshin at gmail.com>wrote:

> void bar (QIODevice& zzz)
> {
>     // ...
>     zzz.close(); // Oops
> }
> void foo ()
> {
>     QTemporaryFile file;
>     bar(file);
> }
> The function bar() may be replaced by anything that doesn't care what type
> I/O object to work with (e.g. QDataStream). "Why the hell does a function
> close an object owned by something else?" is another question, but the idea
> as a whole is simple and obvious -- if a function works with a base class
> (e.g. anything that can act as an I/O device, be it an actual file, memory
> buffer, etc.), the hint "don't call this method because in one of derived
> classes it does not what the name implies" doesn't work.
> On Aug 24, 2013 2:05 PM, "Till Oliver Knoll" <till.oliver.knoll at gmail.com>
> wrote:
>> Am 24.08.2013 um 09:46 schrieb Constantin Makshin <cmakshin at gmail.com>:
>> Overriding a public method to make it private doesn't make much sense
>> because this restriction can be easily circumvented by casting the
>> pointer/reference to a base class (explicitly or by passing it to a
>> function, in the context of this thread, expects a QFile or even more
>> generic QIODevice).
>> Casting? Pointers? Why so complicated?
>> C++ makes this easy for you:
>> #define private public
>> #include "Foo.h"
>> There you go: all private members of class Foo have just become public! A
>> hip hip horray for the preprocessor ;)
>> Oh, by the way: should you feel the urge to pass on this "tip" to someone
>> else: please don't mention my name, will you? ;)
>> But on a more serious note: overriding a public method and make it
>> private is more like a "design decision" and a strong hint to the caller
>> not to call this member on that concrete class instance anymore: why not?
>> Go read the docs! (And if you still feel like calling it: C++ offers you
>> plenty of choices ;))
>> Cheers,
>>   Oliver
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