Initializing fields in constructor – initializer list vs constructor body [duplicate]

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They are not the same if member1 and member2 are non-POD (i.e. non-Plain Old Data) types:

public : Thing(int _foo, int _bar){
    member1 = _foo;
    member2 = _bar;
}

is equivalent to

public : Thing(int _foo, int _bar) : member1(), member2(){
    member1 = _foo;
    member2 = _bar;
}

because they will be initialized before the constructor body starts executing, so basically twice the work is done. That also means, if the type of these members don’t have default constructor, then your code will not compile.

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