[Interest] 64 bit capable QVector

[Philippe]

I could easily guess 99.9% of Qt programmers don't need 64 bit containers... Qt containers are far more than "just convenience" classes.

STL is first of all an interface and there are various implementations, hence your remark about performances does not make sense.

Philippe

On Tue, 3 Sep 2013 14:44:58 -0700
Alex Malyushytskyy <alexmalvtk at gmail.com> wrote:

This question appears on the mailing lists since Qt 3 at least .
> 
> 
> 
> At one point I was disappointed with having signed int restriction, but then I decided 
> 
> that  QT containers are just a convenience classes which are designed to work with either widgets or data of limited size displayed 
> 
> by that widgets.
> 
> 
> 
> If  guaranteed performance is needed you should use STL anyway.
> 
> 
> Regards,
> 
>      Alex
> 
> 
> 
> On Tue, Sep 3, 2013 at 11:58 AM, Constantin Makshin <cmakshin at gmail.com> wrote:
> Thanks for the explanation, although I still don't appreciate the choice
>> (mostly regarding the size, not signedness). :)
>> 
>> On 09/03/2013 10:48 PM, Thiago Macieira wrote:
>> > On terça-feira, 3 de setembro de 2013 22:18:39, Constantin Makshin wrote:
>> >> Could you please explain (or give a link to an article or something like
>> >> that) the reasons Qt developers used to choose signed 32-bit integer for
>> >> this purpose?
>> >> Signed 32-bit container sizes, i.e. number of elements in a container,
>> >> would be acceptable (considering the equation 'n * sizeof(T)' for the
>> >> amount of memory consumed by the array alone) but why use them to
>> >> calculate and store sizes of allocated memory blocks?
>> >
>> > For two reasons:
>> >
>> > 1) it's signed because we need negative values in several places in the API:
>> > indexOf() returns -1 to indicate a value not found; many of the "from"
>> > parameters can take negative values to indicate counting from the end. So even
>> > if we used 64-bit integers, we'd need the signed version of it. That's the
>> > POSIX ssize_t or the Qt qintptr.
>> >
>> > This also avoids sign-change warnings when you implicitly convert unsigneds to
>> > signed:
>> >       -1 + size_t_variable            => warning
>> >       size_t_variable - 1             => no warning
>> >
>> > 2) it's simply "int" to avoid conversion warnings or ugly code related to the
>> > use of integers larger than int.
>> >
>> > io/qfilesystemiterator_unix.cpp:
>> >         size_t maxPathName = ::pathconf(nativePath.constData(), _PC_NAME_MAX);
>> >         if (maxPathName == size_t(-1))
>> >
>> > io/qfsfileengine.cpp:
>> >     if (len < 0 || len != qint64(size_t(len))) {
>> >
>> > io/qiodevice.cpp:
>> > qint64 QIODevice::bytesToWrite() const
>> > {
>> >     return qint64(0);
>> > }
>> >
>> >                     return readSoFar ? readSoFar : qint64(-1);
>> >
>> >
>> >>
>> >> On 09/03/2013 08:42 PM, Thiago Macieira wrote:
>> >>> On terça-feira, 3 de setembro de 2013 19:33:47, Mehmet Ipek wrote:
>> >>>> Btw, size
>> >>>> limit of QVector is 2^31 in 64 bit platforms too?
>> >>>
>> >>> Yes. All Qt container classes use a signed int for sizes.
>> 
>> 
>> 
>> 
>> _______________________________________________
>> Interest mailing list
>> Interest at qt-project.org
>> http://lists.qt-project.org/mailman/listinfo/interest
>> 




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