------- Comment #5 from joseph at codesourcery dot com 2009-01-21 23:27 ------- Subject: Re: Optimisation with inline function causes invalid behaviour
On Wed, 21 Jan 2009, rguenth at gcc dot gnu dot org wrote: > You overflow x and y in main() which invokes undefined behavior. Actually, I don't think this is undefined behavior; I think it's the same as bug 35634. There is no arithmetic on int8_t in C; the values are promoted to int (defined), arithmetic is done on int (which doesn't overflow for the promoted values) and if the values are then stored back in int8_t they are converted back (where the implementation-defined conversions are documented, and it's implementation-defined not undefined). But we know in bug 35634 that GCC is wrongly treating increment/decrement of types such as int8_t as having undefined behavior, by not representing the intermediate promotions and truncations. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38929
