https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68971
--- Comment #2 from joseph at codesourcery dot com <joseph at codesourcery dot com> --- On Thu, 17 Dec 2015, msebor at gcc dot gnu.org wrote: > Paul, the way I prefer to look at it is that the C standard says that constant > expressions are evaluated during translation and when the evaluation overflows > the behavior is undefined. The program is incorrect and the warning helps > find > the bug. That GCC happens to handle it gracefully is a bonus. There are several issues with the standard specification of constant expressions, but my understanding is that all the requirements on constant expressions apply where the syntax specifies that there is a constant expression, not where some expression happens to have operands that are constants but is used in a context not requiring a constant expression. Thus, overflow in an expression of constants, where a constant expression is not required, produces a warning rather than a pedwarn. Furthermore, it seems clear that where a constant expression *is* required, unevaluated subexpressions may contain overflows just as they may contain division by zero (footnote 118).
