On Sat, Feb 4, 2012 at 8:53 AM, Howard Hinnant <[email protected]> wrote: > On Feb 4, 2012, at 5:25 AM, Jean-Daniel Dupas wrote: > >> Hi, >> >> Am I the only one having trouble compiling libc++ with clang TOT. >> For sometime now, clang refuse to compile (and use it) because of the >> following issue: >> >> ../include/ratio:193:19: error: static_assert expression is not an integral >> constant expression >> static_assert(_Xp != nan && _Yp != nan && __a_x <= max / __a_y, >> "overflow in __ll_mul"); >> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >> ../include/ratio:308:13: note: in instantiation of template class >> 'std::__1::__ll_mul<1, 1>' requested here >> __ll_mul<_R1::num / __gcd_n1_n2, _R2::den / __gcd_d1_d2>::value, >> ^ >> ../include/ratio:315:33: note: in instantiation of template class >> 'std::__1::__ratio_divide<std::__1::ratio<1, 1000000000>, std::__1::ratio<1, >> 1000000000> >' requested >> here >> template <class _R1, class _R2> using ratio_divide >> ^ >> ../include/chrono:410:18: note: in instantiation of template type alias >> 'ratio_divide' requested here >> (ratio_divide<_Period2, period>::type::den == 1 && >> ^ >> ../include/chrono:406:9: note: while substituting deduced template arguments >> into function template 'duration' [with _Rep2 = long long, _Period2 = <no >> value>] >> duration(const duration<_Rep2, _Period2>& __d, >> ^ >> ../include/ratio:193:26: note: initializer of 'nan' is not a constant >> expression >> static_assert(_Xp != nan && _Yp != nan && __a_x <= max / __a_y, >> "overflow in __ll_mul"); >> ^ >> ../include/ratio:187:27: note: declared here >> static const intmax_t nan = (1LL << (sizeof(intmax_t) * CHAR_BIT - 1)); >> ^ >> ../include/ratio:187:27: note: declared here >> ../include/ratio:189:27: note: declared here >> static const intmax_t max = -min; > > I haven't noticed because I'm not using TOT clang, and I've been distracted > by libc++abi for the past couple of months. > > But I note the crux of this issue appears to be that this: > > static const intmax_t nan = (1LL << (sizeof(intmax_t) * CHAR_BIT - 1)); > > is no longer consider a compile time constant expression. > > This is one of two things: > > 1. A clang bug. > 2. A standards defect. I.e. this will break a lot of C++03 code if the > standard really says this. > > If it is 2) it would be good for me to know immediately. The next C++ > standards meeting is next week (Feb. 6-10) and it would be good to give such > a defect a high profile/priority at the meeting. > > Does anyone know if this is 1) or 2)?
[expr.shift]p2: [...] if E1 has a signed type and non-negative value, and E1×2E2 is representable in the result type, then that is the resulting value; otherwise, the behavior is undefined. -Eli _______________________________________________ cfe-commits mailing list [email protected] http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
