https://gcc.gnu.org/bugzilla/show_bug.cgi?id=72768
--- Comment #3 from lh_mouse <lh_mouse at 126 dot com> --- > 15.2 Constructors and destructors [except.ctor] > 3 For an object of class type of any storage duration whose initialization or > destruction is terminated by an > exception, the destructor is invoked for each of the object’s fully > constructed subobjects, that is, for each > subobject for which the principal constructor (12.6.2) has completed > execution and the destructor has not > yet begun execution, except that in the case of destruction, the variant > members of a union-like class are not > destroyed. ... Strangely enough, the standard says 'fully constructed' instead of 'completely initialized' here. I tend to consider it a symbol indicating that the committee think the two phrases are distinct from each other. From my point of view, the object is 'completely initialized' once a (delegated or non-delegated, including principle) ctor returns - if an exception is thrown, the dtor shall be called -, despite the principal ctor in progress. The antonym of 'completely initialized' should be 'partially initialized', being in a state when the ctor of a subobject throws an exception， which is not the case here.
