[Bug c/128163] wrong code at -O1: store through the pointer argument of an [[unsequenced]] function declared without a prototype is ignored

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=128163

--- Comment #7 from Drea Pinski <pinskia at gcc dot gnu.org> ---
Created attachment 65956
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=65956&action=edit
Better testcase

Here is a testcase which shows the issue with C23 code in general.