http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56394
Richard Biener <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |RESOLVED Resolution| |INVALID --- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> 2013-02-19 14:26:14 UTC --- (In reply to comment #4) > (In reply to comment #2) > > (In reply to comment #1) > > > Also reproduces with optimization but with -fno-inline. The issue must be > > > with the exact division: > > > > > > D.2616_5 = end.0_3 - beg.1_4; > > > D.2617_6 = D.2616_5 /[ex] 12; > > > > > > the difference is 4088 but that does not divide by 12. Which means your > > > computed end is not correct (the pointers cannot point to elements of > > > an array of Xyz). > > > > That is, you probably want > > > > template<class T> > > T* end() { > > auto e = reinterpret_cast<uintptr_t>(static_cast<char*>(mem) + > > len); > > return reinterpret_cast<T*>(e - len % sizeof(T)); > > } > > > > instead. > > Is there anything wrong with my original code? Yes, pointer subtraction returns an index into an array, but your pointers do not point to array elements but elsewhere. e % sizeof(T) depends on the alignment of e, not on the size of the array. > -- Maxim