On quarta-feira, 7 de março de 2012 17.17.47, Alex Strickland wrote: > On 2012/03/07 03:25 PM, Marc Mutz wrote: > > You shouldn't look at the Qt-project developers when discussing > > interfaces. > > You should look a the Qt programmers in the trenches that happily write > > QColor * c = new QColor(...), as blissfully ignorant of the resource leak > > as they are of Sutter/Alexandrescu. So, Qt can either default to safety > > or it can default to the sharp edge. If you think the latter is > > acceptable, I urge you to run a Qt Open Enrollment training as an > > eye-opener. Hell, I inherited QPtrList publicly when I started out, and I > > would have been glad if the compiler told me I shouldn't do that. > > I'll bite, what is the problem with declaring c this way if I promise to > delete it?
Because even if you're not leaking it, you're using a non-optimal way of doing
things. Since QColor is a value-type class (copyable, comparable, default-
constructible, destructible, no polymorphism), using new there is a waste of
resources -- unnecessary indirection and overhead. In addition to calling the
constructor (most of which are inline), the syntax above needs to allocate
memory, which is a comparatively expensive and non-deterministic operation. It
also adds overhead, an indirection of memory access and potentially a new
cache miss.
All of the value-type classes should be used as pointers if and only if, under
similar circumstances, you'd use a pointer to int too.
So, tell me. Why would you write?
int *i = new int(42);
--
Thiago Macieira - thiago.macieira (AT) intel.com
Software Architect - Intel Open Source Technology Center
Intel Sweden AB - Registration Number: 556189-6027
Knarrarnäsgatan 15, 164 40 Kista, Stockholm, Sweden
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