http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49820
--- Comment #10 from Agner Fog <agner at agner dot org> 2011-07-25 07:43:58 UTC --- I still think that a compiler should be predictable and consistent. It is inconsistent that a+5<a = false produces a warning, while abs(a)<0 = false does not. Both expressions could be intended overflow checks. Besides, some compilers produce a warning when a branch condition is always true or always false. That is sound behavior because it is likely to be a bug. gcc does not produce a warning when optimizing away something like if (2+2 != 4)
