[Bug c++/49813] [C++0x] sinh vs asinh vs constexpr

[rguenther at suse dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49813

--- Comment #14 from rguenther at suse dot de <rguenther at suse dot de> 2011-07-22 11:29:04 UTC ---
On Fri, 22 Jul 2011, paolo.carlini at oracle dot com wrote:

> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49813
> 
> --- Comment #11 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-07-22 11:20:36 UTC ---
> It does *not* Richi, there is an using ::asinh above. Exactly the same for
> sinh.

There is also a using ::asinhf but still std:: provides an
overload.

Please provide a _complete_ standalone testcase that you think should
work and does not (w/o any includes).

I suspect it's because of

DEF_C99_BUILTIN        (BUILT_IN_CASINH, "casinh", 
BT_FN_COMPLEX_DOUBLE_COMPLEX_DOUBLE, ATTR_MATHFN_FPROUNDING)

so if -std=c++0x does not include C99 functions then we have no
implicit builtin support and the following does not work:

extern "C" double asinh(double x);

namespace std {
    using ::asinh;
}

int main()
{
  constexpr double das = std::asinh(1.0);
}

it also does not work with

namespace std {
    double asinh (double x) { return __builtin_asinh (x); }
}

int main()
{
  constexpr double das = std::asinh(1.0);  // Doesn't compile.
}

but it works with

int main()
{
  constexpr double das = __builtin_asinh(1.0);  // Doesn't compile.
}

which means this is still a C++ frontend / library issue.