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Subject: Re: [ub] type punning through congruent base class?
From: Herb Sutter (hsutter_at_[hidden])
Date: 2014-01-16 13:41:25

Matt quoted:

"The lifetime of an object of type T begins when:
— storage with the proper alignment and size for type T is obtained, and
— if the object has non-trivial initialization, its initialization is complete."

Perhaps the necessary fix is to strike “if the object has non-trivial initialization” here. I don’t see why trivial constructors are special – sure, they don’t do anything, but they are notionally important.

A bag of memory of alignment and size suitable for T is-not-a T object until its (possibly trivial) ctor is called on that memory – it seems wrong for that to be true for all T except trivially-constructible T’s (with implicit universal type-punning for all types <= sizeof(T)).


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