[Bug tree-optimization/18487] Warnings for pure and const functions that are not actually pure or const

[sjames at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=18487

--- Comment #33 from Sam James <sjames at gcc dot gnu.org> ---
Another option might be for -fsanitize=undefined to instrument reads and stores
in these functions and trap if they're reached.