stackprotectprologue in cfgexpand.c and stackprotectepilogue in function.c in GNU Compiler Collection (GCC) 4.1 through 8 (under certain circumstances) generate instruction sequences when targeting ARM targets that spill the address of the stack protector guard, which allows an attacker to bypass the protection of -fstack-protector, -fstack-protector-all, -fstack-protector-strong, and -fstack-protector-explicit against stack overflow by controlling what the stack canary is compared against.

The POWER9 backend in GNU Compiler Collection (GCC) before version 10 could optimize multiple calls of the builtindarn intrinsic into a single call, thus reducing the entropy of the random number generator. This occurred because a volatile operation was not specified. For example, within a single execution of a program, the output of every builtindarn() call may be the same.