https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81327
--- Comment #6 from Ville Voutilainen <ville.voutilainen at gmail dot com> --- As stated in the other comments, this breaks *users* of existing Qt versions. Any fix would apply to newer versions only. QVector bit-blasts an object of a type with a virtual table over an object of that same type, so it doesn't change the value of the vptr. It does a cast to void* to try and tell the compiler it knows what it's doing. I don't consider it feasible nor palatable to suggest said users to have to add warning pragmas everywhere they might include QVector. As far as the bit-blast goes, I plan to write a standard change proposal to make it well-defined. Please don't release GCC 8 without fixing this problem.
