[Bug c++/98261] Wrong optimize for virtual function

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98261

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
The bug reporting guidelines tell you to try -fsanitize=undefined before
reporting a bug. That would have told you your code is wrong:

A
d.C:26:14: runtime error: member call on address 0x7ffe71274e18 which does not
point to an object of type 'A'
0x7ffe71274e18: note: object is of type 'B'
 00 00 00 00  28 20 40 00 00 00 00 00  40 20 40 00 00 00 00 00  18 4e 27 71 fe
7f 00 00  00 00 00 00
              ^~~~~~~~~~~~~~~~~~~~~~~
              vptr for 'B'
B