https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64497
--- Comment #2 from Walter Mascarenhas <walter.mascarenhas at gmail dot com> --- What if there is a difference in the expected behavior for this function in C and C++11? Is it not up to g++ for implementing what is mandated in C++11? (This is not a rhetorical question, I really do not know the answer.) In http://man7.org/linux/man-pages/man3/scalbn.3.html it is written that scalbln should return 0 in case of underflow: "If the result underflows, a range error occurs, and the functions return zero, with a sign the same as *x*." On the other hand, http://en.cppreference.com/w/cpp/numeric/math/scalbn states that "If a range error due to underflow occurs, the correct result (after rounding) is returned." I looked at the standard (N3797.pdf) but did not find anything specific about std::scalbln. If there is indeed a discrepancy in the definitions of scalbln in C and C++11 then there may be no bug in libm, and my vendor will not change it. I do not have a copy of the ISO 60599 standard, and I do not know whether the content of the pages http://man7.org/linux/man-pages/man3/scalbn.3.html and http://en.cppreference.com/w/cpp/numeric/math/scalbn are compatible with any standards. Therefore I am in no position to argue, but maybe you could think a bit longer about this.. On Mon, Jan 5, 2015 at 10:29 AM, redi at gcc dot gnu.org < gcc-bugzi...@gcc.gnu.org> wrote: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64497 > > --- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> --- > GCC just calls the scalnlnl() function in libm, so it's not a GCC bug, and > is > not specific to C++ either. I suggest you report it to your libc vendor. > > Complete testcase in C: > > #include <stdio.h> > #include <math.h> > #include <assert.h> > > int main() > { > long double di = scalbnl(1.1L, -16446); > assert( di != 0.0L ); > long double dl = scalblnl(1.1L, -16446L); > assert( dl != 0.0L ); > } > > -- > You are receiving this mail because: > You are on the CC list for the bug. > You reported the bug. >
