https://gcc.gnu.org/bugzilla/show_bug.cgi?id=32667
--- Comment #54 from Richard Biener <rguenth at gcc dot gnu.org> --- (In reply to post+gcc from comment #52) > For the point discussed earlier with the `restrict` in the musl memcpy, I > had another look at the definition of `restrict` and it's not entirely clear > to me any more that there is UB here. The restrict rules only apply to > objects that are "also modified (by any means)". Now the question is, does > "*X = *X" modify the object? Is a write always a modification or only if the > stores representation changes or only if the stored value changes? > > If it requires a representation change, then "memcpy(x, x, n)" does not > modify anything, and hence there is no UB from "restrict". Heh, interesting splitting of hairs ;) I guess you need to file a DR with the language to resolve this question ...
