Richard Guenther wrote:
On Sat, 1 Mar 2008, Richard Kenner wrote:
int f(int a, int b) { return 0 * (a + b); }
get the potentially trapping arithmetic folded away. If -ftrapv is to
have properly defined semantics, those must include trapping if (a + b)
overflows in the above code.
Why? Is there any language that requires such semantics?
Not exactly. -ftrapv semantics are defined _very_ sparsely.
"This option generates traps for signed overflow on addition,
subtraction and multiplication operations."
it doesn't say if it preserves traps on dead code, so Josephs
interpretation is one possible valid one.
And anyway, no point in doing energetic exergesis on vague language
defining an option that has never worked anyway :-)
Part of "fixing" -ftrapv should be to carefully document exactly
what it does/is-intended-to-do (hopefully those are the same :-))
Richard.
