https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96765
Jason Merrill <jason at gcc dot gnu.org> changed:
What |Removed |Added
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CC| |jason at gcc dot gnu.org
--- Comment #2 from Jason Merrill <jason at gcc dot gnu.org> ---
Hmm, is the cast undefined, actually? I thought you were right, but now can't
find any wording to that effect. I see
[expr.static.cast] If the prvalue of type “pointer to cv1 B” points to a B that
is actually a base class subobject of an object of type D, the resulting
pointer points to the enclosing object of type D. Otherwise, the behavior is
undefined.
But this B is a base of a D. Then
[class.cdtor] For an object with a non-trivial constructor, referring to any
non-static member or base class of the object before the constructor begins
execution results in undefined behavior.
but D() has begun execution. Then
[class.cdtor] During the construction of an object, if the value of the object
or any of its subobjects is accessed through a glvalue that is not obtained,
directly or indirectly, from the constructor’s this pointer, the value of the
object or subobject thus obtained is unspecified.
but 'this' in the Base ctor seems to count as obtained indirectly from 'this'
in the Derived ctor.
Then [class.cdtor] paragraph 4 talks about virtual functions, which this is
not.
What rule makes this undefined?
