https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83122
Richard Biener <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Keywords| |diagnostic Status|UNCONFIRMED |NEW Last reconfirmed| |2017-11-23 Ever confirmed|0 |1 --- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> --- Confirmed. The same probably happens with a division. Note it might be an inherent limitation of the warning given apart from some simple cases like yours we can't really tell the value range of the stored value. This is why it says "may" alter its value.