On Tue, 24 Sep 2019, Jakub Jelinek wrote: > On Tue, Sep 24, 2019 at 01:15:46PM +0200, Richard Biener wrote: > > > build_array_type_nelts is only meaningful for non-zero number of elements, > > > for 0 it creates weirdo arrays like char D.2358[0:18446744073709551615]. > > > The following patch uses in that case types like the C FE emits for > > > zero-length array instead (i.e. char D.2358[0:] with forced 0 size). > > > > > > Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk? > > > > Not sure [0:-1] is actually the canonical zero-length array (and IIRC > > what the C++ FE creates and what layout_type can lay out). So why > > You're right, patch withdrawn. > > > not fix the sanitizers instead? > > Well, the problem isn't in sanitizers, but jump threading and late warnings > that are warning even about code specialized by jump threading. > It could be indeed solved with __builtin_warning if we defer the late > warnings and ignore them inside of sanitization report only paths (if we can > detect them reliably, perhaps pass dominated by a failed ubsan or asan > sanitization check), or by making jump threading not try to optimize the > cold sanitization diagnostics parts.
Hmm yeah. Note that in principle the domain could be signed so that the -1 is more obvious. Also [1:0] would be an equally valid empty domain. Not sure if that helps the specific jump-threading case, of course... Richard.
