TL;DR: the bug is due to GCC's optimization feature called full redundancy elimination (FRE). It treats "int a=* pi; * pi=a" as a redundant store and removes i

TL;DR: the bug is due to GCC's optimization feature called full redundancy elimination (FRE). It treats "int a=* pi; * pi=a" as a redundant store and removes it, as explained in the 5th comment: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69776#c5 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69776#c5