[Bug c/112442] Segfault from casting a ptr when using -O2

[schwab@linux-m68k.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112442

--- Comment #5 from Andreas Schwab <schwab@linux-m68k.org> ---
warning: dereferencing type-punned pointer will break strict-aliasing rules
[-Wstrict-aliasing]
   15 |     test((char **)&ptr, "test!");