Default initialization in C++11?

Question

I am not sure which style should I use:

T o; T o{};

Is there difference?

@thesquaregroot, no he doesn't. That's C++11's new initialization syntax. using parentheses results in the most vexing parse — StoryTeller - Unslander Monica
– StoryTeller - Unslander Monica, Commented Dec 24, 2013 at 16:14
I think there are a good minor points here. T o{}; won't work on old compilers, and it may scare some people who are out of touch. — RichardPlunkett
– RichardPlunkett, Commented Dec 24, 2013 at 16:33

Cubbi · Accepted Answer · 2013-12-24 16:23:32Z

7

T o; performs default initialization (in particular, it leaves non-class members uninitialized)

T o{}; performs value initialization (in particular, it zeroes out non-class members)

edited Dec 24, 2013 at 16:23

answered Dec 24, 2013 at 16:15

Cubbi

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7 Comments

user3111311 Over a year ago

What do you mean by non-class members?

Cubbi Over a year ago

@user3111311 members of non-class types (ints, pointers, arrays of such, etc)

RichardPlunkett Over a year ago

remember {} isnt strictly better, the first is potentially faster than the second. and there is little point in setting things to zero if we are about to squash them in the next few lines.

juanchopanza Over a year ago

Note that whether the value initialization zeros out built-ins and PODs can depend on whether T has a user defined default constructor or whether any of the members are initialized at the point of declaration.

Lightness Races in Orbit Over a year ago

@user3111311: You shouldn't "always prefer" anything, ever. Stop looking for mantras to follow: where you find them, they shall serve you poorly.

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